bluuebunny/crossref_metadata_2025 huggingface dataset:
Ionic mechanisms of intestinal electrical control activity
Authors: El-Sharkaway TY , Daniel EE
Published: December 2017

The effects of inhibition and stimulation of the electrogenic Na pump and of altering the ionic environment on the electrical control activity (ECA) were studied in rabbit jejunal smooth muscle. Pump inhibition abolished the ECA at a time when the membrane potential was more negative than the peak depolarization of the control potential (CP). Pump stimulation hyperpolarized the membrane and CP's appeared. Their amplitude was initially small and progressively increased as the hyperpolarization subsided. Lowering external Na to 20 mM or Ca withdrawal, but not addition of verapamil, reversibly abolished the ECA. Chloride replacement by propionate, isethionate, or benzene-sulphonate caused a transient augmentation, followed by suppression of the secondary depolarization of the CP's and decreased their frequency. The initial depolarization of the CP was little affected. Nitrate substitution increased CP frequency and spiking activity but had no observable effects on the CP configuration. These results suggest that the intestinal control potential may result from conductance changes initially to Na and later to C1 rather than fron an oscillatory electrogenic pump.
Renal adaptation to chronic hypocapnia: dietary constraints in achieving H+ retention
Authors: Gougoux A , Kaehny WD , Cohen JJ
Published: December 2017

Previous studies suggested that renal H+ retention during adaptation to hypocapnia might be critically dependent upon concomitant Na and/or K excretion. To test this hypothesis, seven dogs were allowed to recover from hypocapnia while receiving a low electrolyte diet. Despite negligible changes in Na and K excretion, cum delta net acid excretion was --33 meq during adaptation and +44 meq during recovery. Consequently, plasma [HCO3] fell from 19.2 to 14.2 meq/liter in the former and rose from 13.8 to 19.7 meq/liter in the latter groups; these changes were virtually identical to those observed previously in animals maintained on normal electrolyte intakes. These adaptive changes in renal H+ output appeared to be balanced by parallel changes in phosphate excretion. When phosphate retention was prevented during adaptation with Na remaining available for excretion, retention of H+ was still clearly evident. When both phosphate retention and augmented cation excretion were prevented during adaptation, however, H+ retention was abolished. Nevertheless, plasma [HCO3] still fell from 20.9 to 16.2 meq/liter, a level far beyond that attributable to tissue buffering.
Hypothalamic modulation of baroreceptor afferent unit activity
Authors: Adair  , Manning JW
Published: December 2017

Unit responses to sinus nerve stimulation were recorded in the medulla. A conditioning stimulus to the posterior hypothalamus produced inhibition of 65% of unit responses to sinus nerve stimulation as early as 7 ms and extending as long as 790 ms after conditioning; 50% recovered after 300 ms. Unit responses to hypothalamic stimulation alone were also recorded in the medulla, some in the same loci as other unit responses to sinus nerve stimulation. They could be activated by contralateral as well as ipsilateral hypothalmic stimulation and showed recurrent bursts of firing over a 1,000-ms poststimulus interval. Evoked potentials and unit responses were recorded in the posterior hypothalamus, some occurring within 10--20 ms poststimulation of the sinus nerve, indicating that baroreceptor information is ascending in a time sufficiently short to involve the hypothalamus in reflex regulation of blood pressure as well as more generalized homeostatic responses which include the cardiovascular system.
Pressure dependence of the mechanical properties of arteries in vivo
Authors: Cox RH
Published: December 2017

Simultaneously measurements of intra-arterial pressure and external diameter were recorded from the thoracic and abdominal aortas, the carotid, brachiocephalic, left subclavian, and femoral arteries of anesthetized dogs. Data were recorded under control conditions and during efferent vagal stimulation, and were used to compute values of wall geometry, mechanical properties, phase velocity, and characteristic impedance. Values of these parameters computed for both control and vagal stimulation were used to represent their dependence on mean arterial pressure. Both the dynamic elastic modulus and the phase velocity increased with mean pressure at each arterial site. Values of computed characteristic impedance were constant and independent of mean arterial pressure between 80--150 mmHg. The tropical application of norepinephrine (100 mug/ml) to the femoral artery produced no change in mean pressure, while external diameter and dynamic modulus were decreased, and characteristic impedance was increased. These results provide direct support for the conclusion of previous studies on vascular impedance spectra which suggested a constancy of characteristic impedance with changes in mean arterial pressure.
Development of circadian periodicity in base and stress levels of corticosterone
Authors: Levin R , Levine S
Published: December 2017

Base and stress levels of corticosterone were assessed at 4-h intervals over a 24-h period in male and female rats at age 18, 22, and 26 days. A significant periodicity in base levels of corticosterone is present at 22 days of age; however, a rhythm in stress values does not appear until age 26 days. At age 26 days the pattern of the circadian periodicity in both base and stress concentrations of corticosterone resembles that of the mature rhythm.
Interstitial fluid pressure and alkaline gastric secretion
Authors: Altamirano M , Requena  , Perez TC
Published: December 2017

The interstitial fluid pressure of the submucosa of the gastric fundus was monitored by means of Guyton's capsules in dogs anesthetized with pentobarbital. The intracapsular pressure (ICP) was measured during secretion produced by: a) hypertonic solutions placed inside the stomach; b) arterial hypertension (200 mmHg) applied during intra-arterial infusion of histamine, and c) intra-arterial infusion of acetylcholine. The first procedure did not modify the ICP. On the other hand, whenever interstitial fluid appeared in the gastric lumen during hypertension plus histamine, the mean ICP increased, mostly due to augmented capillary filtration. The hydraulic coefficient measured in these experiments was at least 4 orders of magnitude larger than the respective osmotic coefficient. The action of acetylcholine was complex: large doses enlarged the net capillary filtration, but small doses increased the mean ICP by muscle stimulation only. Contraction of the muscularis mucosae might be the most important mechanism underlying bulk flow of interstitial fluid in physiological conditions. It is concluded that hydraulic gradients across the epithelium might account for the "secretion" of "alkaline" juice.
Feeding induced by intracerebroventricular 2-deoxy-D-glucose in the rat
Authors: Miselis RR , Epstein AN
Published: December 2017

Feeding was induced with lateral intracerebroventricular (ICV) injections of 2-deoxy-D-glucose (2-dg), a glucose analogue causing glucoprivation. Feeding increased rapidly by an average of 2.6 g following ICV 2-DG (2.9 or 5.8 mg per rat), but did not increase after ICV D-glucose or sucrose. At the same doses, 2-DG did not increase feeding when given peripherally. Core temperature dropped in a dose-dependent manner with doses of 2-DG sufficient to induce feeding after peripheral administration, but did not occur with ICV injections. The 2-DG (0.006--1.219 M) did not stimulate feeding when infused bilaterally into the lateral hypothalamus, the preoptic area, or the anterior lateral hypothalamus. Nor did it produce feeding when injected into the ventromedial hypothalamus at the same sites and in the same rats in which procaine HC1 caused increased feeding. The brain, therefore, is directly sensitive to glucoprivation in the control of feeding, and glucoprivation alone is sufficient to mobilize feeding behavior. The specific site of sensitivity to glucoprivation and the mode of action of the glucoprivic system in the brain are unknown.
Alpha-Glycerol phosphatase and glycerol kinase activities in tissues of the silkmoth Hyalophora cecropia during the larval-pupal transformation
Authors: Jungreis AM , Dailey JC , Hereth ML
Published: December 2017

Magnesium metabolism has been studied in Hyalophora cecropia during the larval-pupal transformation (LPT) (Jungreis, A. M., Am. J. Physiol. 224: 27--30, 1973). Throughout this period, it accumulated in midgut (0.5 M at ecdysis), presumably as osmotically inactive Mg3(PO4)2. Glycerol accumulation in hemolymph was also first noted during this period. Since total alpha-glycerol phosphate present in hemolymph declined between the larval and pupal stages of development, the relationship between magnesium and alpha-glycerol phosphate metabolism was studied. Specific and total alpha-glycerol phosphatase (degradative) and glycerol kinase (synthetic) enzyme activities were measured in fat-body and midgut tissue throughout the LPT. At both feeding larval and diapause pupal stages in development in both tissues, total glycerol kinase activity is greater than that of alpha-glycerol phosphatase with degradative/synthetic activity ratios of 0.2--0.5. In fat body, ratios remained constant or shifted in the direction of synthesis during the LPT, whereas those measured in midgut tissue increased in the direction of degradation with a maximum ratio of 5.8 noted following spinning. The increase in degradative/synthetic activity ratios in midgut tissue is attributed to a greater rate of loss of glycerol kinase than alpha-glycerol phosphatase enzyme activity. Orthophosphate, presumably released from alpha-glycerol phosphate within the cells of the pharate pupal midgut tissue, combines with magnesium to form osmotically inactive Mg3(PO4)2 crystals.
Fluoride absorption from the rat urinary bladder: a pH-dependent event
Authors: Whitford G. M. , Pashley D. H. , Reynolds K. E.
Published: December 2017

Urinary bladder absorption of stable and radiofluoride was studied as a function of pH in anesthetized rats to further evaluate the influence of pH gradients on fluoride transport. Buffered pH values and stable fluoride concentrations ranged from 1.85 to 7.90 and from 0.012 to 8.81 mM, respectively. [14c]inulin served as a marker for solute concentration changes due to water migration or dilution. The results indicate that bladder fluoride absorption is inversely related to pH over the 1.85–5.50 range. Mean, 15-min radiofluoride absorption values of 70% at pH 1,85, 37% at pH 3.95, and 5% at pH 5.50 WERE OBSERVED. These fractional absorption values were not significantly influenced by carrier fluoride concentration, the buffers used, or the presence of urine. Above pH 5.50, pH-independent absorption occurs to a slight extent. The results are consistent with a first-order absorptive process which occurs by the nonionic diffusion of hydrogen fluoride.
Effect of acute unilateral renal denervation on tubular sodium reabsorption in the dog
Authors: Nomura G. , Takabatake T. , Arai S. , Uno D. , Shimao M. , Hattori N.
Published: December 2017

The effects of acute denervation of the kidney on renal tubular sodium and water excretion were studied in anesthetized, hypophysectomized, and cortisone-treated mongrel dogs during stable water diuresis produced by the infusion of 2.5% dextrose. In all experiments, denervation natriuresis, and diuresis were observed without significant change in glomerular filtration rate (GRF) and renal plasma flow (RPF). Fractional sodium delivery to the distal nephron (CNa + CH2O/100 ml GFR) and fractional free water clearance (CH23/100 ml GFR) was significantly greater in the denervated kidney compared with the innervated kidney (9.6+/-1.2 vs. 6.7+/-0.9% and 8.8+/-1.2 vs. 6.5+/-0.8%, respectively). Distal tubular sodium reabsorption (CH2O/(CNa + CH2O)) was not significantly different. We conclude that renal denervation primarily affects the proximal tubule as manifested by a decrease in the reabsorption of sodium and water. A small effect of denervation on the distal nephron is not completely ruled out.
Effect of NaCl on composition and volume of cells of the rat papilla
Authors: Morgan T.
Published: December 2017

The composition and volume of the cells of an isolated rat papilla were measured in media in which NaCl was varied from 150 to 600 mM; KCl, from 2 to 20 mM; or which contained mannitol, 300 mM. Change in NaCl from 150 to 600 mM reduced cell volume by 25%, increased cell Na+ content by 250% but had no significant effect on cell potassium concentration or content. Increases in K+ concentration in the media did not affect cell water or cell sodium, but the cell potassium rose by an amount approximately 3 times the increase in the medium concentration. Mannitol reduced cell volume; the cell content of sodium and potassium did not alter, but the concentration of Na+ and K+ altered reciprocally with the change in cell volume. Similar changes were observed with liver slices. This study indicated that papillary cells maintain osmotic equilibrium by the accumulation of sodium. This accumulation may influence the metabolic activity of the medullary and papillary cells.
Renal sugar transport in the winter flounder. III. Two glucose transport systems
Authors: Kleinzeller A. , Dubyak G. R. , Griffin P. M. , McAvoy E. M. , Mullin J. M. , Rittmaster R.
Published: December 2017

Teased renal tubules of the winter flounder (Pseudopleuronectes americanus) were employed to investigate the structural requirements for two pathways of D-glucose transport which take place preponderantly across the basal (antiluminal) face of renal cells. 1) An inhibition analysis of the equilibrating, Na-independent and phlorizin-sensitive transport of the nonmetabolizable methyl-alpha-D-glucoside (0.1 and 0.5 mM), with 20 glucose analogs (5 mM), was employed to establish the structural requirements for the substrate-carrier interaction: a (pyranose) ring, oxygen, or F at C1, C2-OH, C3-OH, and C4-OH (all axial, 1C model). Some interaction may also occur at C6-OH. D-Glucose shares this transport system. Hydrogen bonding between the oxygens and the carrier is suggested. 2) The phloretin- and phlorizin-sensitive, ouabain-insensitive transport of D-glucose, 2-deoxy-D-glucose, and D-mannose is associated with considerable phosphorylation. The three sugars mutually compete for a shared transport site. The specificity pattern characterizing the transport system defines the following structural requirements: a (pyranose) ring, a free C1-OH, C3-OH, and C4-OH (both axial) and possibly C6-OH. Hydrogen bonding between the carrier and the oxygens at C3, C4, and C6, and covalent bonding at C1 is suggested.
Mechanism of dopamine-induced diuresis in the dog
Authors: Cadnapaphornchai P. , Taher S. M. , McDonald F. D.
Published: December 2017

This study was undertaken to evaluate the effect of dopamine (D) on renal water excretion. Intravenous (i.v.) infusion of D (7.5 microgram/kg per min) was associated with a significant, reversible increase in free water excretion (CH2O) and a decrease in urinary osmolality (Uosmol). These changes, however, were associated with significant increases in renal blood flow (RBF), glomerular filtration rate (GFR), and urinary sodium excretion (UNaV). These increases could have been responsible for the diuretic response to D. To examine whether D has a direct effect on vasopressin (ADH) release, D was infused into one common carotid artery at a dose equal to one-fourth the i.v. dose. No effects on CH2O and Uosmol were observed. To examine whether D might have an antagonistic effect on ADH a single bolus of ADH (100 mU) was given to the same hypophysectomized dogs with and without D infusion. The antidiuretic response to ADH was the same, whether or not D was given concomitantly. The net changes in Uosmol and CH2O in response to ADH were not significantly different. Taken together, the present results provide no evidence for a direct effect of D on ADH release nor do they indicate an interference with the peripheral action of ADH. The dopamine-induced diuresis is probably the result of increased solute excretion. This, in turn, is the result of the combined effects of dopamine on increasing renal blood flow, GFR, and sodium excretion.
Mechanism of angiotensin II-induced proteinuria in the rat
Authors: Bohrer M. P. , Deen W. M. , Robertson C. R. , Brenner B. M.
Published: December 2017

To investigate the mechanism(s) of angiotensin II-induced proteinuria, polydisperse [3H]dextran (D) (radius = 18-42 A) was infused into seven Munich-Wistar rats before and during intravenous infusion of angiotensin II (AII), 0.35 microgram/kg per min. During AII infusion, UprotV rose approximately twofold, and the fractional clearances of D [(U/P)D/(U/P)In] increased significantly for dextrans with radii greater than 22 A. Single nephron filtration fraction increased, due to a measured rise in the glomerular transcapillary hydraulic pressure difference from 34 to 43 mmHg. Near constancy of single nephron glomerular filtration rate resulted, however, from the offsetting effect of a decrease in glomerular plasma flow rate from 83 to 60 nl/min. These measured hemodynamic changes were found, by the use of pore theory, to account to a large extent for the measured increases in (U/P)D/(U/P)In. In seven other rats, fractional clearances of polyanionic dex-ran sulfate (a more reliable marker of albumin filtration than D) were also found to increase significantly with AII, suggesting that the proteinuria induced by AII can be explained, in large part, by hemodynamic factors.
Evidence for glomerular actions of ADH and dibutyryl cyclic AMP in the rat
Authors: Ichikawa I. , Brenner B. M.
Published: December 2017

Experiments were performed on 54 chronically water diuretic Munich-Wistar rats to investigate the effects of various antidiuretic peptides on the determinants of glomerular ultrafiltration. Transition from water diuresis to antidiuresis, induced either by intravenous infusion of 1) exogenous peptides (Pitressin, synthetic arginine vasopressin, or synthetic [1-deamino,4-valine]-8-D-arginine vasopressin) or 2) dibutyryl cyclic AMP, or by stimulation of endogenous ADH release by acute, mild arterial hemorrhage, was associated with near-constant or decreased values for single nephron (SN) and total kidney GFR. Nevertheless, the glomerular transcapillary hydraulic pressure difference (deltaP) uniformly increased with antidiuresis, due to consistent reductions in Bowman's space hydraulic pressure rather than to increases in glomerular capillary hydraulic pressure, the former a consequence of the fall in urine flow rate. In all antidiuretic states, the rats were uniformly observed to be at filtration pressure disequilibrium, permitting calculation of unique values of the glomerular ultrafiltration coefficient (Kf). These values of Kf in antidiuresis were invariably lower than the values obtained during water diuresis. Whether these effects of ADH and DBcAMP on deltaP and Kf represent physiological influences in the control of GFR remains uncertain; their offsetting effects in the present studies usually failed to alter GFR appreciably.
Effect of volume expansion with NaCl or NaHCO3 on nephron fluid and Cl transport
Authors: Galla J. H. , Beaumont J. E. , Luke R. G.
Published: December 2017

To assess the influence of plasma anions on nephron fluid and chloride transport following volume expansion (VE), rats were studied by micropuncture technique during hydropenia and after VE with NaCl (CVE) or NaHCO3 (BVE). VE with either solution produced increments in plasma volume, SNGFR, and fractional sodium excretion (FENa), and decrements in proximal and distal TF/P inulin ratio which were not different. The proximal transepithelial chloride ratio decreased similarly in CVE (from 1.34 to 1.16) and BVE (from 1.32 to 1.17). Following VE, proximal fractional Cl reabsorption decreased similarly in both CVE (-5.9%) and BVE (-7.4%). Early distal fractional Cl reabsorption also was decreased in CVE (-12%) but not in BVE (-1%). Fractional chloride excretion increased in CVE but not in BVE. Therefore, following VE plasma anion composition did not significantly modify either fluid reabsorption in proximal tubule or loop of Henle or urinary Na excretion. The fraction of sodium reabsorbed with chloride in the proximal tubule increased, and Cl conservation, primarily within the loop of Henle, can be maintained despite marked natriuresis.
Failure to abolish reactive hyperemia by indomethacin in denervated kidneys of rabbits
Authors: Aizawa C. , Honda N.
Published: December 2017

The effect of indomethacin (10 mg/kg) on the distribution of cortical blood flow during postocclusive reactive hyperemia was evaluated in denervated kidneys of anesthetized rabbits by the radioactive microsphere technique. Renal denervation caused a slight but not significant increase in renal blood flow with no remarkable alteration in the distribution of cortical blood flow. After release of 1-min occlusion of the renal artery, hyperemic responses developed with a fractional flow redistribution toward the inner cortex. The absolute perfusion rate increased in the inner cortex but did not significantly change in the outer cortex. Indomethacin produced a decrease in renal blood flow despite elevated blood pressure. Even in the indomethacin-treated animals, postocclusive reactive hyperemia appeared concomitantly with the fractional flow redistribution to the inner cortex. The percentage repayment by reactive hyperemia of ischemia during the artery clamping was not significantly different before and after indomethacin administration. The findings indicate that indomethacin did not significantly affect the postocclusive vascular response in denervated kidneys of rabbits, thereby giving evidence against the role of prostaglandins as mediators of reactive hyperemia.
Transient response of glomerular filtration rate and renal blood flow to step changes in arterial pressure
Authors: Jackson T. E. , Guyton A. C. , Hall J. E.
Published: December 2017

Measurement of rapid renal hemodynamic changes were made for 90 s in pentobarbital-anesthetized dogs following step increases and decreases in renal arterial pressure between 80 and 120 mm Hg. Transient analysis was used to observe time characteristics of the autoregulatory relationships which are obscured in steadystate measurements. Temporal decoupling of blood flow and glomerular filtration rate (GFR) occurred with both step increases and decreases of arterial pressure. Steady-state autoregulation of blood flow was attained in about 30 s, whereas steady-state autoregulation of GFR was not demonstrably attained even 90 s after the arterial pressure maneuver. The temporal decoupling of renal blood flow and GRR supports the concept of transient involvement of proximal tubular dynamics and efferent resistance changes during acute autoregulation of GFR following step changes in arterial pressure.
Tubular sites of potassium regulation in the normal and uninephrectomized rat
Authors: Bengele H. H. , Evan A. , McNamara E. R. , Alexander E. A.
Published: December 2017

Tubular handling of potassium was studied in the Charles River CD (cesarean derived) rat by clearance, micropuncture, and anatomic techniques. The following groups were evaluated: group I, hydropenia; group II, KCl-mannitol infusion; group III, 10% body wt saline loading; group IV, uninephrectomy, hydropenia; and group V, uninephrectomy, saline loading. Comparison of micropuncture samples from early and late distal collection sites (LDCS) and urine collections revealed no net K transport along the distal convoluted tubule in groups I and III-V but net addition of K in all groups beyond the LDCS. Absolute K secretion beyond the LDCS appeared to be flow dependent in groups I-III. The LDCS was noted by light and electron microscopy always to be lined with collecting tubule epithelium. We conclude that no net change in potassium transport occurs along the superficial distal convoluted tubule during hydropenia or saline loading in normal or uninephrectomized Charles River CD rats, but secretion is demonstrable during KCl infusion. Net addition of potassium beyond the LDCS was noted in all groups and this addition was enhanced by uninephrectomy.
Effect of phosphate deprivation on renal phosphate transport in the dog
Authors: Wen S. F. , Boynar J. W. , Stoll R. W.
Published: December 2017

In order to examine the role of dietary intake of phosphate in regulating renal phosphate transport, clearance and micropuncture studies were performed in 25 dogs with various duration of phosphate deprivation induced by low phosphate diet and aluminum hydroxide gel. In phosphate deprivation of 17-41 days duration, the phosphaturic response to extracellular volume expansion (ECVE) was blunted in the intact group and was virtually abolished in the acutely thyroparathyroidectomized (TPTX) group. With longer phosphate deprivation of 53-110 days, no phosphaturia occurred after ECVE or administration of parathyroid hormone (PTH), even with intact parathyroids. These alterations in phosphaturic responses did not correlate with the plasma phosphate but rather with the duration of phosphate deprivation. Fractional proximal tubule phosphate reabsorption was enhanced in phosphate deprivation and the proximal tubule fluid-to-ultrafilterable phosphate ratio appeared to be a good index for the degree of phosphate deprivation. Acute infusion of phosphate to raise plasma phosphate slightly above normal did not completely restore the responsiveness to ECVE. It is concluded that the adaptive response to phosphate deprivation occurs in both proximal and distal nephron segments and that factors other than plasma phosphate are primarily responsible for such an adaptation.
Renal response of the starling (Sturnus ;ulgaris) to an intravenous salt load
Authors: Braun E. J.
Published: December 2017

Total kidney GFR's, urine flow, inorganic ion excretion, and single nephron glomerular filtration rates (SNGFRs) were evaluated in anesthetized starlings under control conditions (2.5% mannitol infusion) and in starlings subjected to an osmotic stress induced by the intravenous infusion of 5.8% sodium chloride. Under control conditions the GFR was 2.92 ml/kg per min, urine flow 0.20 ml/kg per min, 63% of filtered sodium was reabsorbed, mean mammalian type (MT) SNGFR was 15.6 nl/min, and mean reptilian type (RT) SNGFR was 7.0 nl/min. During osmotic stress the GFR did not change, urine flow increased to 3 times the control level, the percentage of filtered sodium reabsorbed did not change, both the mean MT SNGFR (24.3 nl/min) and the mean RT SNGFR (10.3 nl/min) were significantly higher than the control levels. During the osmotic stress more MT and fewer RT nephrons were filtering than during control conditions. Under control conditions 98.5% of the sodium excreted by the kidney was associated with uric acid. This percentage decreased as the osmotic stress increased. The starlings tended to excrete the osmotic load imposed by the infusion of NaCl to prevent the plasma osmolality from increasing.
Determinants of proximal tubular reabsorption as mechanisms of glomerulotubular balance
Authors: Tucker B. J. , Blantz R. C.
Published: December 2017

The determinants of absolute proximal reabsorption (APR) were studied in four groups of rats during hydropenia, partial renal vein occlusion (RVO), saline expansion, and RVO after saline expansion. Nephron filtration rate (SNGFR), nephron plasma flow (RPF), APR, and proximal tubule (Pt) peritubular capillary (HPc), and interstitial (HPi) hydrostatic pressures were measured by micropuncture techniques. Subcapsular space (pii) and star peritubular capillary (piE) oncotic pressures were also determined. The peritubular capillary permeability coefficiency (LpAR) and the corresponding effective reabsorptive pressure (ERP) were computed, where APR = LpAR . ERP, and ERP = net reabsorptive pressure across the peritubular capillary. The results indicate that APR correlates best with SNGFR (P less than 0.05), but not with (pii - HPi), RPF, or LpAR. There was a significant relationship between piE and LpAR, where LpAR fell with increases in piE (P less than 0.01). In conclusion, 1) changes in absolute proximal reabsorption correlate best with changes in nephron filtration rate but not with (pii - HPi) across this range of values, 2) changes in efferent oncotic pressure (piiE) correlated inversely with LpAR, and 3) glomerulotubular balance in the proximal tubule can be partially attributed to intraluminal factors.
Tetracycline-induced inhibition of Na+ transport in the toad urinary bladder
Authors: Guzzo J. , Cox M. , Kelley A. B. , Singer I.
Published: December 2017

The effects of three tetracyclines, demethylchlortetracycline (DMC), minocycline (MNC), and oxytetracycline (OTC), on Na+ transport (measured as short-circuit current) were examined in toad urinary bladders mounted in modified Ussing chambers. During a 1-h incubation period serosal DMC (but not MNC or OTC) inhibited basal Na+ transport, whereas MNC (but not DMC or OTC) inhibited ADH-stimulated Na+ transport. MNC also inhibited cyclic AMP-stimulated Na+ transport. During longer incubation periods all three drugs inhibited basal Na+ transport. The DMC-induced inhibition of basal Na+ transport and the MNC-induced inhibition of ADH-stimulated Na+ transport were paralleled by an inhibition of the active conductance of the bladders. Thus, although all three drugs inhibit basal Na+ transport, only MNC inhibits ADH-stimulated Na+ transport. This effect does not correlate with the known effects of the tetracyclines on ADH-stimulated water flow or with drug-protein binding, and may be related to the greater lipid solubility of MNC.
Antidiuretic hormone-induced intramembranous alterations in mammalian collecting ducts
Authors: Harmanci Mehmet C. , Kachadorian William A. , Valtin Heinz , DiScala Vincent A.
Published: December 2017

Freeze-fracture electron microscopy had previously revealed antidiuretic hormone-induced aggregates of intramembranous particles in amphibian urinary bladder. To investigate the effects of antidiuretic hormone (ADH) in another ADH-sensitive epithelium, namely, mammalian renal collecting ducts, freeze-fracture studies were carried out in Brattleboro homozygous rats. Collecting duct luminal membranes of ADH-treated homozygotes showed intramembranous particle clusters (117 ± 17/100 μm2) that were loosely packed and that occurred on both exoplasmic (E) and protoplasmic (P) faces. Untreated, control homozygous rats had significantly less (3 ± 1/100 μm2) clusters. Changes similar to those seen in ADH-treated rats were observed in water-deprived Wistar rats. The clustered particles differed from those seen in ADH-treated amphibian urinary bladder in that the latter occurred only on the P face and were more densely packed. Nevertheless, our observations suggest a common membrane effect for ADH action that may apply in mammals and amphibia alike.

freeze-fracture; Brattleboro homozygous rats; membrane particle clusters

Submitted on March 6, 1978

Accepted on July 14, 1978
Importance of chloride for acute inhibition of renin by sodium chloride
Authors: Kirchner K. A. , Kotchen T. A. , Galla J. H. , Luke R. G.
Published: December 2017

To evaluate the contribution of chloride to acute renin inhibition by sodium chloride, plasma renin activity (PRA) was measured before and after peripheral venous infusion of NaCl, NaHCO3, NaBr, NaNO3, lysine monohydrochloride, or lysine glutamate in NaCl-deprived rats. In contrast to controls and animals infused with other sodium salts, PRA decreased (P less than 0.01) after infusion with NaCl [from 28.3 +/- 2.8 to 13.3 +/- 1.8 ng/ml per h (SE)] and NaBr (from 40.6 +/- 6.2 to 21.8 +/- 3.9 ng/ml per h), and renal tubular halide reabsorption increased (P less than 0.05). Arterial pressure, plasma volume, inulin clearance, net sodium balance, serum Na+ and K+, and pH were not different among sodium-loaded groups. PRA was also suppressed (P less than 0.01) by infusion with lysine monohydrochloride (from 51.6 +/- 5.4 to 32.4 +/- 5.1 ng/ml per h) but not with lysine glutamate. These results suggest that inhibition of renin by sodium is dependent on an intrarenal effect of chloride. During infusion with sodium salts which suppressed renin, negative free water clearance (TcH2O) increased, whereas infusion with sodium salts that did not inhibit renin resulted in either no change or decreased TcH2O. The association of renin inhibition and increased TcH2O indirectly supports the hypothesis that renin suppression by chloride is related to the magnitude of absorptive chloride transport in the thick ascending limb of the loop of Henle.
Cholinergic agents inhibit sodium transport across the isolated toad bladder
Authors: Wiesmann W. , Sinha S. , Yates J. , Klahr S.
Published: December 2017

Acetylcholine and carbamylcholine (carbachol) inhibited sodium transport across the toad bladder. This effect was blocked by atropine. Carbachol increased the uptake of 45Ca by isolated toad bladder epithelial cells. This increased 45Ca uptake was blocked by atropine, pentobarbital, or lanthanum chloride. The inhibitory effect of cholinergic agents on sodium transport was dependent on external calcium concentration and was abolished by decreasing external calcium from 2 to 0.2 mM or by agents (pentobarbital, lanthanum chloride) which prevent the movement of calcium into cells. Carbachol increased modestly, but significantly, the levels of cyclic GMP in isolated toad bladder epithelial cells. This effect was blocked by atropine. Whether the decrease in sodium transport produced by cholinergic agents is the result of increased intracytoplasmic calcium levels, increased cyclic GMP levels, or a combination of both remains to be established.
Response of deep nephrons and the terminal collecting duct to a reduction in renal mass
Authors: Buerkert J. , Martin D. , Prasad J. , Chambless S. , Klahr S.
Published: December 2017

Juxtamedullary (JM) nephron and collecting duct function was studied after a two-thirds reduction in renal mass in the young rat. The glomerular filtration rate of JM nephrons was twofold greater in the remnant kidney (RK) group than in controls, but this increase was proportional to the increase measured in surface nephrons. Despite an increase in absolute reabsorption, delivery of sodium and water to the end of the proximal tubule of superficial nephrons and to the bend of Henle's loop of JM nephrons was increased. This was a consequence of an increase in filtered load and a decrease in fractional reabsorption. Potassium handling in surface nephrons was similar to that of sodium and water. In deep nephrons of the RK group, potassium delivery to the bend was increased as a consequence of increased filtered load. The terminal portion of the collecting duct has a role in this adaptive response to a reduction in renal mass. In rats with a RK, reabsorption of water occurred along this segment; however, when the amount reabsorbed was related to delivery, fractional water reabsorption was only 30% of controls. Changes in sodium handling were more profound. In the group with the RK, sodium reabsorption was not detectable along this segment. Thus, while 40% of delivered sodium was reabsorbed in controls, in the remnant kidney group the mean was not different from zero (-1.7%).
Maturational development of glomerular ultrafiltration in the rat
Authors: Ichikawa I. , Maddox D. A. , Brenner B. M.
Published: December 2017

To ascertain the cause of low glomerular filtration rate in newborn and immature mammals, we measured glomerular pressures and flows directly in immature (30- to 45-day-old) euvolemic Munich-Wistar rats with surface glomeruli. As with total kidney GFR, single nephron (SN)GFR was found to be significantly lower than in adult rats, on average by 40% when corrected for kidney weight. Equality between efferent oncotic pressure and transglomeruler hydraulic pressure difference (deltaP) was usually achieved in immature rats, indicating that the glomerular capillary ultrafiltration coefficient is not a factor limiting SNGFR and GFR in immature rats. Although the average values for deltaP in immature rats were slightly, albeit significantly, lower than in adults, markedly lower values (79 +/- 5 vs. 136 +/- 10 nl/min per g kidney wt) for glomerular plasma flow rate (QA) proved to be the primary factor responsible for the lower SNGFR and GFR values in immature rats. Considerably higher values for afferent and efferent arteriolar resistances contributed to this low QA state in immature rats.
Possible role of cytosolic calcium and Na-Ca exchange in regulation of transepithelial sodium transport
Authors: Taylor A. , Windhager E. E.
Published: December 2017

Emerging evidence in a number of different epithelia suggests that changes in cytosolic calcium ion levels play a critical role in the regulation of transepithelial sodium transport. Maneuvers believed to raise cytosolic calcium ion activity lead to an inhibition of net sodium transport in toad urinary bladder, frog skin, and isolated perfused proximal renal tubules. Regulation of the level of ionized calcium in the cytosol of the epithelial cells appears to involve a process of coupled Na-Ca exchange across the basolateral plasma membrane, energized, at least in part, by the sodium gradient. It is suggested that changes in cytosolic calcium ion levels, secondary to changes in Na-Ca exchange, in turn dependent in part on the activity of the sodium pump, constitute a link in a negative feedback mechanism. Through such a feedback mechanism, the rate of entry of sodium into the cell across the apical surface may be kept in step with its rate of extrusion across the basolateral surface.
Action of adenosine on chloride active transport of isolated frog cornea
Authors: Spinowitz B. S. , Zadunaisky J. A.
Published: December 2017

Addition of adenosine (10–7 to 10–4 M) to the tear side of isolated corneas (Rana catesbeiana) produced a rapid, sustained increase in short-circuit current, potential difference, and radioisotopic chloride net flux. The increased net chloride flux accounted for the increased short-circuit current. Adenosine, a known activator of adenyl cyclase in other tissues, exerted its effects on chloride transport through a receptor different from the one described for epinephrine and prostaglandins in the corneal epithelium. Propranolol inhibited the epinephrine response but not the adenosine effect. Dipolyphloretin phosphate inhibited prostaglandin responses but did not affect the adenosine stimulation of chloride transport. Adenine and/or ribose, parts of the adenosine molecule, had no stimulatory effect, but 5'-AMP had a partial effect.The activation of the chloride pump with DBcAMP blocked the response to adenosine. Adenosine interacted with the effects of theophylline. Adenosine, a naturally occurring molecule, stimulated chloride transport by activation of adenyl cyclase through a separate membrane receptor in the corneal eqithelium.
Renal nerves in compensatory renal response to contralateral renal denervation
Authors: DiBona G. F. , Rios L. L.
Published: December 2017

Acute unilateral renal denervation and the resultant antidiuresis and antinatriuresis are accompanied by a compensatory antidiuresis and antinatriuresis from the opposite kidney. The present study tested the hypothesis that the renal sympathetic nerves mediated this adaptive response. In the volume-expanded rat, acute left renal denervation increased left kidney fractional sodium excretion from 4.4 +/- 0.6 to 5.9 +/- 0.6%, while right kidney fractional sodium excretion decreased from 4.3 +/- 0.6 to 3.5 +/- 0.5%. Subsequent acute right renal denervation increased right kidney fractional sodium excretion from 3.5 +/- 0.5 to 4.7 +/- 0.6%. Measurement of efferent left renal sympathetic nerve activity before and after acute right renal denervation showed an increase from 10.9 +/- 0.8 to 16.0 +/- 1.4 Hz. When both kidneys were simultaneously subjected to acute renal denervation, fractional excretion of sodium increased bilaterally. In uninephrectomized rats subjected to acute denervation of the remaining kidney, fractional excretion of sodium increased. Glomerular filtration rate was unchanged throughout in all studies. These results demonstrate that the compensatory renal response to acute contralateral renal denervation is mediated by the efferent renal sympathetic nerves.
Intraluminal and contraluminal magnesium on magnesium and calcium transfer in the rat nephron
Authors: Quamme G. A. , Dirks J. H.
Published: December 2017

Magnesium and calcium transport was studied in the superficial proximal tubule, loop of Henle, and superficial distal tubule of the rat by in vivo microperfusion. Magnesium chloride was used to vary plasma and perfusate magnesium concentration. Perfusion with magnesium-free Ringer solution resulted in little magnesium entry into the tubule lumen in either normomagnesemic or hypermagnesemic rats. Magnesium concentration increased with water abstraction along the perfused proximal tubule whether markedly above or below plasma concentrations. Absolute proximal magnesium reabsorption increased with perfusate concentration; however, fractional magnesium and calcium reabsorption decreased in proportion to net sodium reabsorption with elevated extracellular magnesium. Magnesium absorption increased in the loop of Henle proportional to luminal magnesium concentration. Sodium and calcium reabsorption was not affected. Acute elevation of plasma magnesium, however, significantly depressed absolute magnesium reabsorption to a greater degree than calcium whereas sodium was unchanged. The effects of extracellular magnesium onloop reabsorption were reflected in the final urine. Reabsorption of sodium, calcium, and magnesium in the perfused distal tubule was concentration-dependent and not altered by luminal or extracellular magnesium concentration.
Dynamics of ascites formation in rats with experimental cirrhosis
Authors: Lopez-Novoa J. M. , Rengel M. A. , Hernando L.
Published: December 2017

Renal function, sodium balance, and ascites formation were observed during induction in rats of experimental cirrhosis. The same variables were studied after partial removal of the ascites in rats with experimental cirrhosis. Glomerular filtration rate (GFR) and effective renal plasma flow (RPF) did not change during hepatic cirrhosis development. Positive sodium balance significantly higher than that observed in controls preceded the appearance of ascites for a period of about 2 wk. When the ascites was removed, GFR, RPF and positive Na balance did not change if Na intake remained constant. Ascites reformation rate was largely dependent on sodium balance. These data strongly support the "overflow" theory of ascites formation and are difficult to reconcile with the classical "underfilling" theory.
Renal renin responses to changes in volume status and perfusion pressure
Authors: Kaufman J. S. , Hamburger R. J. , Flamenbaum W.
Published: December 2017

The effects on juxtaglomerular apparatus (JGA) renin activity of maneuvers known to acutely alter renin secretory rates were studied in rats. Five groups of rats were studied: group I: control; group II: 1% volume expansion; group III: 10% volume expansion; group IV: hypotensive hemorrhage; and group V: aortic clamping. Superficial (S) JGA renin activity was decreased in group II and further decreased in group III. Deep (D) JGA renin activity did not change. After hypotensive hemorrhage both S- and D-JGA renin activity increased. Similar results were seen after aortic clamping, although the increase in D-JGA renin activity was significantly less. These results indicate that S- and D-JGA renin activity may be under the control of different stimuli and may vary independently. They also support the concept that acute changes in renin secretion may be related to changes in renin synthesis.
Proximal tubule glucose efflux in the rat as a function of delivered load
Authors: Knight T. F. , Senekjian H. O. , Sansom S. C. , Weinman E. J.
Published: December 2017

The effect of altering the delivered load of glucose by either increasing the rate of perfusion or the initial glucose concentration on the absorptive flux of glucose was examined in rat proximal tubule using the in vivo microperfusion technique. The passive flux coefficient was determined to be 1.27 pmol . min-1 . mm-1 . mM-1 glucose concentration gradient. With initial glucose concentrations of either 11.1 or 22.2 mM, the glucose flux increased as the rate of perfusion was increased. At similar rates of perfusion, glucose flux was higher from 22.2 mM glucose solution than from the 11.1 mM solution. Estimation of the driving force for passive glucose efflux indicates that the increase in glucose efflux when flow rate is increased cannot be accounted for by passive changes in efflux out of the proximal tubule. When large transepithelial glucose gradients are imposed across the tubule, passive glucose flux plays a more significant role, but cannot totally account for higher rates of glucose efflux observed with the perfusion solution containing 22.2 mM glucose. These results are considered in light of the recent model of the flow dependency of nonelectrolyte absorption of Barfuss and Schafer [Am. J. Physiol. 236 (Renal Fluid Electrolyte Physiol. 5): F163–F174. 1979].
Concentration of urine in the absence of ADH with minimal or no decrease in GFR
Authors: Edwards B. R. , Gellai M. , Valtin H.
Published: December 2017

It is known that large (more than 50%) reductions in glomerular filtration rate (GFR) can lead to formation of hyperosmotic urine in the absence to depend critically upon reduced delivery of luid to the loops of Henle. In the present study, we tried to determine whether a much lesser decrease in GFR could also result in hyperosmotic urine when ADH is absent. The following mean values (control vs. 3 h of partial aortic constriction) were obtained in 21 conscious diabetes insipidus rats: GRF, 909 +/- 35 (SE) vs. 835 +/- 49 microliter . min-1 . 100 g body wt-1 (8% decrease; P less than 0.02); urinary osmolality (Uosmol), 125 ”/- 6 vs. 309 +/- 14 mosmol/kg H2O (P less than 0.001; peak Uosmol 350 +/- 22). Analysis of individual responses revealed that Uosmol increased as much when there was no measurable decrease in GFR as when such decrease occurred. Neither GFR nor filtration fraction bore any systematic relationship to Uosmol or to each other. We conclude that in the absence of ADH Uosmol can increase with minimal or no change in GFR. Changes in filtration fraction--a potential mediator of reduced delivery to the loops--could not explain the increased Uosmol, even in those instances in which GFR remained unchanged.
Mechanism of activation of renal Na+-K+-ATPase in the rat: effects of reduction of renal mass
Authors: Jacobson M. P. , Rodriguez H. J. , Hogan W. C. , Klahr S.
Published: December 2017

The mechanism of activation of renal Na+-K+-ATPase was studied in rats 2 wk after unilateral nephrectomy. The increase in enzyme specific activity was confined to the outer medulla and occurred without changes in the cellular contents of RNA or protein. Enzyme activation was accompanied by increases in the levels of the phosphorylated intermediate with little or no change in the apparent turnover numbers of the reaction. The specific activity of the ouabain-sensitive p-nitrophenylphosphatase also increased by uninephrectomy but to a larger extent than did Na+-K+-ATPase. Kinetic studies demonstrated an increase in Vmax for ATP, sodium, and potassium, and small increases in Km for ATP and K1/2 for potassium. There was no change in the activation energies or phase transition temperature to indicate alterations in the membrane environment of Na+-K+-ATPase. Adrenalectomy did not adversely affect activation. These results indicate that activation of renal Na+-K+-ATPase after reduction of renal mass occurs mainly by an increase in the number of sodium pump sites.