bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Na+ intake on dopamine-induced inhibition of renal cortical Na(+)-K(+)-ATPase
Authors: Seri I. , Kone B. C. , Gullans S. R. , Aperia A. , Brenner B. M. , Ballermann B. J.
Published: December 2017

The enzyme L-amino acid decarboxylase (L-AADC), found in abundance in rat proximal tubule cell cytosol, converts L-dopa to dopamine. Dopamine, in turn, suppresses proximal tubule sodium transport by inhibiting Na(+)-K(+)-ATPase activity. We sought to determine whether changes in dietary sodium intake in rats lead to adaptation of dopamine formation and dopamine-induced Na(+)-K(+)-ATPase inhibition. In rats on a high-salt (HS) diet, the maximal velocity (Vmax) of renal cortical L-AADC was 78 +/- 19% higher than that in rats on a low-salt (LS) diet. The Michaelis constant (Km) of the enzyme remained unchanged. In renal cortical tubule cell suspensions the L-dopa-induced inhibition of ouabain-sensitive oxygen consumption (QO2) was significantly greater in rats on HS diet than in rats on LS diet. Furthermore, L-dopa completely inhibited the nystatin-induced rise in QO2 in the HS but not in the LS group. Carbidopa, an inhibitor of L-AADC, abolished the L-dopa-induced inhibition of nystatin-stimulated QO2 in cells from HS rats and was without significant effect in cells from LS rats. L-Dopa-stimulated K+ efflux was greater in cells from HS rats at 28 +/- 1 nmol.min-1.mg protein-1, compared with 7 +/- 6 nmol.min-1.ng protein-1 in cells from LS rats. By contrast, ouabain-stimulated K+ efflux did not differ between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Role of ANG II in eicosanoid production by isolated glomeruli from rats with bilateral ureteral obstruction
Authors: Yanagisawa H. , Morrissey J. , Morrison A. R. , Purkerson M. L. , Klahr S.
Published: December 2017

The production of prostaglandin (PG) E2, 6-keto-PGF1 alpha, and thromboxane B2 (TxB2) under basal conditions and after exposure to angiotensin II (ANG II) or arginine vasopressin (AVP) was examined in vitro in isolated glomeruli. The glomeruli were obtained from control rats and rats with bilateral ureteral obstruction (BUO) of 24-h duration that were pretreated or not with an inhibitor of the angiotensin I converting enzyme (ACE). Basal prostanoid production was greater in isolated glomeruli from BUO rats than in controls. Administration of an ACE inhibitor, enalaprilat, given in vivo returned basal prostanoid production by isolated glomeruli of BUO rats to levels seen in glomeruli of control rats. The prostanoid production in response to addition of ANG II or AVP in vitro was blunted in glomeruli from BUO rats, but the response was restored to “normal” after blockade of ANG II synthesis in vivo in BUO rats. Blockade of ANG II synthesis in vivo did not affect prostanoid synthesis by isolated glomeruli of control rats. The prostanoid generation in response to addition of both ANG II and arachidonic acid in vitro compared with ANG II addition alone was not significantly stimulated in glomeruli from BUO rats. In contrast, it was significantly stimulated in glomeruli of control rats. The results indicate that endogenous ANG II has an important role in the increased synthesis of prostanoids found in isolated glomeruli of rats with BUO and that the in vitro prostanoid production in response to ANG II and AVP can be restored to normal when the synthesis of ANG II is inhibited in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)
A potassium channel in the apical membrane of rabbit thick ascending limb of Henle's loop
Authors: Wang W. H. , White S. , Geibel J. , Giebisch G.
Published: December 2017

We used the patch-clamp technique to study the activity of single potassium channels in the apical membrane of isolated thick ascending limbs of Henle's loop (TAL) of rabbit kidneys. In cell-attached patches with NaCl Ringer or high-K+ solution in the bath and 140 mM K+ in the pipette, an inwardly rectifying K+ channel was observed with an inward slope conductance of 22.0 +/- 0.5 pS and outward slope conductance of 10.2 +/- 0.3 pS at 22 degrees C (n = 15). The channel was highly selective for K+, with a calculated permeability ratio for K(+)-to-Na+ of 20:1 (n = 4). The open probability (Po) of the channel was 0.89 +/- 0.03 (n = 15) and was not voltage dependent. In inside-out patches with 140 mM K+ in both the bath and the pipette solutions, both Po and conductance of the channel were similar to that in cell-attached patches. Addition of 0.1 mM Ba2+ to the pipette solution reduced Po of the channel in a voltage-dependent manner. Lowering the pH of the bath solution from 7.4 to 6.9 or increasing Ca2+ concentration from 0 to 0.5 mM in inside-out patches did not alter either Po or conductance of the channel. Addition of 2 mM ATP to the bath solution completely inhibited channel activity. This ATP-induced inhibition was fully reversible and was found to be dependent on the ratio of ATP to ADP, since adding 1 mM ADP to the bath solution relieved the ATP-induced blockade. The property of this small-conductance K+ channel make it a likely candidate for recycling of K+ across the apical membrane of TAL of the rabbit kidney. ATP and ADP are possible intracellular regulators of the channel's activity.
D-penicillamine and the transport of L-cystine by rat and human renal cortical brush-border membrane vesicles
Authors: Furlong T. J. , Posen S.
Published: December 2017

Brush-border membrane vesicles (BBMV) were prepared from rat and human renal cortical tissue by magnesium aggregation and differential centrifugation, and the uptake of L-cystine, L-cysteine, and L-cysteine-D-penicillamine were assessed by a rapid-filtration technique. L-Cystine uptake was relatively sodium independent and associated with membrane binding. Sodium-stimulated uptake was sensitive to a cation but not anion diffusion potential. Both sodium-independent and sodium-stimulated uptake rates were inhibited by the cationic L-amino acids and by some neutral L-amino acids. The uptake rates of L-cysteine and L-cysteine-D-penicillamine were more sodium dependent, and sodium-stimulated uptake rates were more sensitive to cation and anion diffusion potentials. Neither the sodium-independent nor the sodium-stimulated uptake rates of L-cysteine or L-cysteine-D-penicillamine were inhibited by the cationic L-amino acids. L-Cysteine-D-penicillamine showed relatively little membrane binding. It is concluded that L-cystine is transported into renal cortical BBMV by pathways distinct from those concerned with the transport of L-cysteine and L-cysteine-D-penicillamine, and it is postulated that these differences may account for some of the effects of D-penicillamine in cystinuria.
Direct effects of endothelin in the rat kidney
Authors: Katoh T. , Chang H. , Uchida S. , Okuda T. , Kurokawa K.
Published: December 2017

In the present study, we tested the direct effects of endothelin (ET) on rat kidney in vivo. ET was infused into the left renal artery of anesthetized rats at a rate of 0.5, 5, 20, or 40 pmol/h. ET reduced ipsilateral urine volume (V), clearance of inulin (CIN), and clearance of p-aminohippuric acid (CPAH) in a dose-dependent manner. Thus ET at 20 pmol/h did not change V but decreased renal plasma flow (RPF) and glomerular filtration rate (GFR) by 27.6 +/- 14.3 and 30.8 +/- 10.4%, respectively, in the ipsilateral kidney. ET at 0.5 pmol/h was without effect and at 5 pmol/h had only minor effects on CIN and CPAH of ipsilateral kidney. At 40 pmol/h, ET reduced ipsilateral V, GFR, and RPF by 52.3 +/- 21.4, 58.4 +/- 14.5, and 72.5 +/- 10.6%, respectively. Filtration fraction and fractional excretion of Na remained unchanged during ET infusion. ET, 40 pmol/h, infused into the renal artery together with atrial natriuretic peptide (ANP) at a rate of 12 pmol/h reduced the ipsilateral V, GFR, and RPF by 33.2 +/- 6.3, 26.1 +/- 6.0, and 27.2 +/- 7.1%, respectively, decrements less than those with ET alone. When a calcium-channel blocker nicardipine was infused at a rate of 2.5 micrograms/h into the renal artery together with ET, 20 pmol/h, there was little change in the ipsilateral V, RPF, and GFR; ET, 40 pmol/h, with nicardipine did not change V and decreased GFR and RPF by 25.9 +/- 5.6 and 23.1 +/- 10.8%, respectively, decrements less than those without nicardipine.(ABSTRACT TRUNCATED AT 250 WORDS)
Atrial natriuretic peptide differentially modulates T- and L-type calcium channels
Authors: McCarthy R. T. , Isales C. M. , Bollag W. B. , Rasmussen H. , Barrett P. Q.
Published: December 2017

Atrial natriuretic peptide (ANP) inhibits the secretion of aldosterone stimulated by any of these major physiological agonists: angiotensin II, adrenocorticotropic hormone, or K+. The stimulatory actions of each of these agonists depend on calcium influx through voltage-dependent calcium channels. Because two types of calcium channels have been previously described in bovine glomerulosa cells (T- and L-type), the patch-clamp technique was used to evaluate the effect of ANP on each voltage-dependent calcium channel type. ANP was found to differentially modulate these two channel types, stimulating L-current while inhibiting T-current. Inhibition of T-current resulted from a shift in the voltage dependence of inactivation to more negative potentials within the physiological range. These results indicate that the ANP-induced inhibition of aldosterone secretion may be partially mediated via a reduction of the calcium current through T-type channels.
Tubuloglomerular feedback responses during peritubular infusions of calcium channel blockers
Authors: Mitchell K. D. , Navar L. G.
Published: December 2017

Experiments were performed in pentobarbital-anesthetized rats to evaluate the dependence of the effector limb of the tubuloglomerular feedback mechanism on transmembrane calcium flux through potential-operated calcium channels. Peritubular capillary infusions of the calcium channel blockers, verapamil and nifedipine, were used to achieve high intrarenal levels without influencing arterial blood pressure. Proximal tubule stop-flow pressure (SFP) and single-nephron glomerular filtration rate (SNGFR) tubuloglomerular feedback responses were obtained during control conditions and during simultaneous peritubular capillary infusion with an isotonic saline solution containing either verapamil or nifedipine. Infusion of either 10(-3) M verapamil or 10(-3) M nifedipine, at a rate of 20 nl/min, increased resting SFP (measured during conditions of zero distal volume delivery) and markedly attenuated both the SFP and SNGFR feedback responses to a late proximal perfusion rate of 30 nl/min. Infusion of verapamil (10(-3) M) also increased the slope of the relationship between SFP and renal arterial perfusion pressure between 80 and 120 mmHg (0.43 +/- 0.03 vs 0.24 +/- 0.02, P less than 0.001, n = 10). These findings support the hypothesis that the preglomerular contractile elements responsive to signals from the macula densa cells are activated by calcium influx through potential-operated calcium channels. Furthermore, the preglomerular contractile elements sensitive to calcium channel blockers can dilate further even when orthograde flow to a single macula densa segment is interrupted.
Effects of vasoactive agents on uptake of immunoglobulin G complexes by mesangial cells
Authors: Singhal P. C. , Santiago A. , Satriano J. , Hays R. M. , Schlondorff D.
Published: December 2017

Mesangial handling of immune complexes may be important in immune injury. We examined whether vasoactive agents, independent of hemodynamic effects, could directly influence uptake of immunoglobulin G (IgG) complexes by mesangial cells (MC). Under basal conditions, MC took up more gold particles coated with IgG2b (P less than 0.05) than coated with IgG2a. Preincubation of MC with angiotensin II (ANG II) (5 x 10(-7) M) resulted in enhancement of uptake (P less than 0.05) of IgG2b-gold [7,578 +/- 968 counts per minute (cpm) per well], IgG2a-gold (4,566 +/- 295 cpm/well; P less than 0.01), and bovine serum albumin (BSA)-gold (2,532 +/- 66; P less than 0.05) when compared with respective controls (IgG2b-gold, 5,513 +/- 762 cpm/well; IgG2a-gold, 3,282 +/- 439; BSA-gold, 2,279 +/- 97). Cytochalasin B produced a significant reduction of uptake of IgG2b-gold (2,224 +/- 88 cpm/well) when compared with the uptake by control cells (3,711 +/- 287 cpm/well) (P less than 0.05). Pretreatment of MC with atrial natriuretic peptide (ANP, 10(-9) M) slightly decreased uptake of IgG-gold under basal conditions (P less than 0.05) and decreased the response to ANG II (P less than 0.05). Similarly, dopamine (DA, 10(-6) M) attenuated uptake of IgG2b-gold under basal (P less than 0.01) as well as ANG II-stimulated (P less than 0.01) states. ANP increased mesangial guanosine 3',5'-cyclic monophosphate (cGMP), DA, adenosine 3',5'-cyclic monophosphate (cAMP) content.(ABSTRACT TRUNCATED AT 250 WORDS)
Identification of individual renocortical cells that secrete renin
Authors: Carey R. M. , Geary K. M. , Hunt M. K. , Ramos S. P. , Forbes M. S. , Inagami T. , Peach M. J. , Leong D. A.
Published: December 2017

Successful application of the reverse hemolytic plaque assay was developed to identify individual renocortical cells that secrete renin directly. The plaque assay was validated by a number of established criteria. Using this technique, we demonstrate an increase in renin secretion with beta-adrenergic stimulation and an inhibition of renin secretion with extracellular calcium in groups of renin-secreting cells. Transmission electron microscopy of the cell in the center of a hemolytic plaque demonstrated a modified vascular smooth muscle cell with densely packed secretory granules. Electron microscopy immunocytochemistry demonstrated the presence of renin in the secretory granules, confirming the identity of the cell as a renal juxtaglomerular cell. The technology developed here has allowed the precise identification and study of the individual renin-secreting juxtaglomerular cell.
The 11 beta-OHSD inhibitor, carbenoxolone, enhances Na retention by aldosterone and 11-deoxycorticosterone
Authors: Morris D. J. , Souness G. W.
Published: December 2017

Carbenoxolone sodium, CS, a liquorice derivative associated with hypertension and sodium retention, has been demonstrated to inhibit 11 beta-hydroxysteroid dehydrogenase, an enzyme that metabolizes cortisol and corticosterone to their respective inactive 11-dehydro products (cortisone and 11-dehydrocorticosterone). It has been proposed that the increased bioavailability of unmetabolized corticosterone and cortisol following 11 beta-OHSD inhibition allows these steroids to act on renal mineralocorticoid receptors to elicit the mineralocorticoid action. Here we describe how CS amplifies the antinatriuretic activity of aldosterone and deoxycorticosterone; the latter steroid is of particular importance in that it does not possess a hydroxyl group at the C-11 position in the steroid ring, indicating that another mechanism(s) in addition to 11 beta-OHSD inhibition is responsible for the amplification of the action of deoxycorticosterone.
Peritubular capillary permeability and intravascular RBC aggregation after ischemia: effects of neutrophils
Authors: Hellberg P. O. , Kallskog O. T. , Ojteg G. , Wolgast M.
Published: December 2017

The influence of neutrophils on peritubular capillary permeability and intravascular red blood cell (RBC) aggregation after renal ischemia was studied in anesthetized Sprague-Dawley rats. Intraperitoneal administration of antineutrophil serum (ANS) reduced the number of neutrophils in the blood to 3% of normal. The control group received an equal volume of inactive serum. Renal macromolecular capillary permeability was studied from 1) extravasation of albumin and 2) plasma to lymph transport of plasma proteins and of neutral and negatively charged lactate dehydrogenase (LDH). The net driving force (NDF) for fluid transfer over the peritubular capillary membrane was determined by the micropuncture technique. The intrarenal distributions of neutrophils and RBC were measured by a histochemical method and 51Cr-labeled RBC, respectively. Under preischemic control conditions neither macromolecular permeability nor renal clearance of inulin was affected by ANS. However, the steep increase in the macromolecular transport from plasma to lymph resulting from 45 min of ischemia and reperfusion was blunted by ANS, and preischemic control values were restored after 1 h of recirculation. In the control group the mass transport of plasma proteins increased twofold and that of both neutral and negatively charged LDH fourfold. NDF was equal in the two groups. In the ANS-treated animals the intrarenal neutrophil content was only 2% of the control. Neutrophils were found mainly in the cortex, whereas RBC aggregation was observed only in the renal medulla. It is concluded that neutrophils mediate postischemic capillary leakage. It is suggested that this leakage underlies RBC aggregation and incomplete return of blood flow in the renal medulla after ischemia.
Regulation of renin release and renal hemodynamics during acute and chronic verapamil administration
Authors: Young D. B. , Lin H. B. , LeDuff J. K.
Published: December 2017

The effects of short- and long-term administration of the calcium-entry blocker verapamil on regulation of renal hemodynamics and renin release were analyzed in anesthetized dogs at controlled levels of renal perfusion pressure between 110 and 60 mmHg. The following three groups of dogs were studied: a control group, an acutely treated verapamil group (initial dose of 150 micrograms/kg followed by 4 micrograms.kg-1.min-1), and a chronically treated verapamil group (240 mg per os twice each day). At 110 mmHg the renal blood flow (RBF) in the acutely and chronically treated groups was 53% greater than (P less than 0.03) and 79% greater than (P less than 0.01) that of the control group. Glomerular filtration rate (GFR) in the acutely and chronically treated groups was 64 and 92%, respectively, greater than (P less than 0.01 for both) that of the control group. Autoregulation of RBF and GFR was extremely effective in the control group, whereas it was severely impaired by acute and long-term treatment with verapamil. Renin release at 110 mmHg in the control and the acutely treated groups were similar, 3.36 +/- 0.96 and 4.46 +/- 0.64 U.min-1.g-1, respectively, although in the chronically treated group the rate of release was 8.89 +/- 2.60 U.min-1.g-1 (P less than 0.03). As perfusion pressure was reduced, the rate of release from the acutely treated group rose to higher levels than that of the control group; at 70 mmHg release from the acutely treated group was 88% greater than that of the control group (P less than 0.01). Verapamil profoundly alters regulation of renal hemodynamics and renin release and the effect is prominent during both short- and long-term administration.
Effects of amino acid isomers on canine renal hemodynamics
Authors: Premen A. J. , Dobbins D. E.
Published: December 2017

The major objective of this study was to ascertain whether the renal hemodynamic response to amino acid infusion in dogs is stereospecific. To test this hypothesis, we examined the renal hemodynamic effects of two isomers (L and D) of an amino acid mixture of serine, alanine, and proline (SAP; 0.051 mmol.kg-1.min-1) in anesthetized dogs. Intravenous infusion of L-SAP (n = 6) significantly elevated renal blood flow (RBF) and glomerular filtration rate (GFR) by 33 +/- 3 and 30 +/- 5%, respectively, over 1 h. DL-SAP (n = 6) elevated RBF and GFR by only 14 +/- 3 and 13 +/- 3%, respectively. Yet D-SAP (n = 6) failed to elevate either RBF or GFR over 1 h. Intravenous mannitol (940 mos-mol/kg; osmotic control; n = 6) also failed to elevate renal hemodynamics. In six other dogs, intrarenal infusion of L-, but not D-, SAP marginally elevated RBF and GFR by 13 +/- 2 and 12 +/- 2%, respectively, over 1 h. Infusion of alpha-aminoisobutyric acid (0.051 mmol.kg-1.min-1; n = 6), an amino acid analogue that is cotransported with sodium but not metabolized by renal cells, elevated RBF and GFR by 22 +/- 5 and 18 +/- 6%, respectively, over 1 h. These data indicate that vascular infusion of L, but not D, isomers of amino acids elevate RBF and GFR. We therefore suggest the importance of amino acid stereospecificity in the renal vascular response to amino acid infusion in dogs.
Effect of cellular acidosis on cell volume in S2 segments of renal proximal tubules
Authors: Sullivan L. P. , Wallace D. P. , Clancy R. L. , Grantham J. J.
Published: December 2017

The presence of pH-sensitive transport mechanisms in the basolateral membrane of proximal tubular cells suggests that cell volume and its regulation may be sensitive to changes in cell pH. We have measured the response of cell pH and cell volume to changes in the acid-base composition of solutions bathing isolated, lumen-collapsed, proximal S2 tubular segments taken from the rabbit kidney. Cell pH was determined by measurement of the fluorescence emission of 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. Cell volume was calculated from measurements of tubular diameter. An increase in CO2 from 5 to 15% reduced cell pH 0.30 units and raised cell bicarbonate concentration ([HCO3]) 10 mM. Cell volume rose to 108.6% of control in 4 min. A decrease in bath [HCO3] from 25 to 5 mM reduced cell pH 0.41 units and cell [HCO3] by 15 mM. Cell volume gradually increased to 105.7% at 8 min. The rate of the regulatory volume decrease after cell swelling on exposure to a 160 mosM solution was determined in the presence of 5 and 15% CO2. The latter reduced the maximum fractional rate of recovery of volume from 0.18 to 0.11 min-1 but did not affect the extent of regulation. We conclude that acidosis causes cell swelling and reduces the rate of volume regulation in response to hypotonic media.
In situ localization of renin and its mRNA in neonatal ureteral obstruction
Authors: el-Dahr S. S. , Gomez R. A. , Gray M. S. , Peach M. J. , Carey R. M. , Chevalier R. L.
Published: December 2017

Angiotensin II is an important mediator of renal vasoconstriction resulting from chronic unilateral ureteral obstruction (UUO). Distribution of renin mRNA and immunoreactive renin (IR) was examined in kidneys of 1-mo-old Sprague-Dawley rats subjected to either sham operation (n = 21), left complete UUO (n = 21), or right uninephrectomy (UNX, n = 16) at 2 days of age. There were no differences among the three groups in mean arterial pressure or plasma renin activity. Unlike sham kidneys, in which IR was detected in less than 55% of juxtaglomerular apparatuses (JGA) and was confined to a juxtaglomerular location, IR in both kidneys of animals with UUO appeared in greater than 75% of JGA and extended along most of the length of the afferent arteriole (P less than 0.01). In contrast, IR in kidneys of UNX rats was localized to the JGA as in sham-operated animals. Compared with sham-operated kidneys, renal renin content was increased in the obstructed kidneys (P less than 0.01) but decreased in the intact opposite kidneys of UUO rats and in the remaining kidneys of UNX rats (P less than 0.05). Renin mRNA, detected by in situ hybridization histochemistry, was localized to the JGA in kidneys of all groups. However, the fraction of JGA containing detectable renin mRNA was higher in obstructed kidneys than in intact opposite, UNX, or sham kidneys (P less than 0.05). In conclusion, UUO alters intrarenal renin independent of the systemic renin-angiotensin system. The greater distribution of IR, increased renin content, and renin gene expression of kidneys with ipsilateral UUO are consistent with a role for renin-angiotensin in mediating the vasoconstriction resulting from UUO.
Dopamine stimulation of cAMP production in cultured opossum kidney cells
Authors: Cheng L. , Precht P. , Frank D. , Liang C. T.
Published: December 2017

Dopamine receptors have been identified in many tissues including the kidney. To establish an in vitro system as a model for dopamine action, we studied the effect of dopamine (DA) receptor agonists and antagonists on adenosine 3',5'-cyclic monophosphate (cAMP) formation in opossum kidney (OK) cells. The stimulation of cAMP production in these cells by dopamine was dose dependent, and markedly higher levels were observed in the presence of dopamine plus a phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine. Half-maximal stimulation was found with 1.15 +/- 0.22 microM dopamine. A DA1-receptor agonist, SKF 82526J, stimulated cAMP production, whereas a DA2-receptor agonist, Ly 171555, did not. The stimulatory effects of dopamine and SKF 82526J were abolished by a specific DA1-receptor antagonist, Sch 23390 with half-maximal inhibition concentrations of 1.24 +/- 0.18 and 4.0 +/- 0.5 nM, respectively. In contrast, the DA2-receptor antagonist, spiperone, had no inhibitory effect on dopamine- and SKF 82526J-stimulated cAMP production. Beta-Adrenergic antagonists failed to attenuate the stimulatory effects of dopamine and SKF 82526J on cAMP production. In addition, the beta-adrenergic receptor agonist, isoproterenol, did not stimulate cAMP production. These results suggest that the action of dopamine was not mediated through beta-adrenergic receptors. Furthermore, our results clearly demonstrated the existence of DA1-receptors linked to adenylate cyclase in OK cells.
Transport of urate and p-aminohippurate in rabbit renal brush-border membranes
Authors: Martinez F. , Manganel M. , Montrose-Rafizadeh C. , Werner D. , Roch-Ramel F.
Published: December 2017

The mechanisms involved in urate and p-aminohippurate (PAH) transport in the rabbit renal brush-border membrane were investigated through study of membrane vesicles. Transport of [14C]urate and [3H]PAH was measured by a rapid filtration method. As previously reported by others, no OH(-)-PAH exchanger could be demonstrated by imposing an outwardly directed OH- gradient (pHin 7.4, pHout 6). In contrast, an OH(-)-lactate exchanger (or H(+)-lactate cotransport) was demonstrated. In the presence of valinomycin and an inwardly directed K+ gradient, both [14C]urate and [3H]PAH vesicle uptake were stimulated, demonstrating a potential-driven transport of these two anions. Probenecid, PAH, or cold urate decreased potential-driven urate uptake, suggesting that this transport was facilitated by a specific transport mechanism. The potential-driven urate transport described here may play a role in the second step of urate secretion in rabbits, because rate (or PAH) is transported across the brush-border membrane from the negative interior of the cell to the more positive omen.
Transport characteristics of renal brush border Na(+)- and K(+)-dependent uridine carriers
Authors: Lee C. W. , Cheeseman C. I. , Jarvis S. M.
Published: December 2017

The uptake of uridine into rat renal brush-border membrane vesicles is mediated by Na(+)- and K(+)-dependent concentrative transport processes. At a 100 mM extravesicular cation concentration the apparent Km values were 9.7 +/- 4.2 and 28 +/- 5 microM, and Vmax values were 28 +/- 4 and 7 +/- 1 pmol.mg protein-1.s-1 for the Na(+)- and K(+)-dependent systems, respectively. Uracil, D-ribose, and D-glucose failed to inhibit the uptake processes, indicating that these carriers are specific for nucleosides. Other purines and pyrimidines inhibited uridine uptake competitively, although these two transport systems seem to favor adenosine and pyrimidines as permeants. Evidence is also given that transport is rheogenic, involving a net transfer of positive charge. The Na+:uridine and K+:uridine coupling stoichiometry was found to be 1:1 and 3:2, respectively. Both systems can also be driven by an anion gradient with apparent NO3- affinity (KNO3-) values of 42 +/- 13 and 163 +/- 54 mM for Na(+)- and K(+)-dependent systems, respectively.
Effects of modulation of renal kallikrein-kinin system in the nephrotic syndrome
Authors: Hutchison F. N. , Martin V. I.
Published: December 2017

Albuminuria (UAlbV) can be reduced by converting-enzyme inhibitors (CEI), but the hormonal mechanism responsible for this effect has not previously been defined. Since CEI increase kinin activity as well as reduce angiotensin II (ANG II) activity, experiments were performed to determine the effect of isolated alterations in kinin and ANG II metabolism on UAlbV in rats with passive Heymann pephritis. Phosphoramidon was used to potentiate kinin activity without altering ANG II synthesis. Aprotinin was utilized in combination with the CEI, enalapril, to prevent the increase in kinin activity caused by CEI. UAlbV and the fractional renal clearance of albumin (FCAlb) decreased significantly after either phosphoramidon or enalapril, although only enalapril reduced blood pressure. Glomerular filtration rate (GFR) was not affected by either drug. Phosphoramidon did not affect plasma renin activity (PRA) or the pressor response to angiotensin I (ANG I), indicating that ANG II synthesis was not altered. Aprotinin prevented the reduction in UAlbV and FCAlb produced by CEI but not the hypotension, elevated PRA, or ANG I pressor blockade produced by CEI. Aprotinin alone had no effect on UAlbV, GFR, PRA, or blood pressure. UAlbV can be reduced by increasing kinin activity by a mechanism that is not dependent on suppression of ANG II activity or reduction in GFR or blood pressure. CEI may reduce proteinuria as a result of their action on the kallikrein-kinin system rather than on the renin-angiotensin system.
Regulation of renal Na(+)-H+ exchanger by cAMP-dependent protein kinase
Authors: Weinman E. J. , Steplock D. , Bui G. , Yuan N. , Shenolikar S.
Published: December 2017

Octyl glucoside-extracted rabbit renal brush-border membrane (BBM) proteins were sequentially fractionated using anion exchange chromatography, and the fractions were tested for Na(+)-H+ exchange activity, amiloride sensitivity, and the effect of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase (PKA) after reconstitution into artificial lipid vesicles. Compared with the initial protein extract, an anionic protein fraction eluting with 0.2-0.4 M NaCl (fraction B) demonstrated increased Na(+)-H+ exchange activity. Fraction B also demonstrated sensitivity to inhibition by amiloride but was not regulated by PKA. Co-reconstitution of fraction B with a BBM protein fraction highly enriched in a 42-kDa polypeptide restored the inhibitory response to PKA. These experiments suggest that, as assayed in a solubilized and reconstituted system, the Na(+)-H+ exchanger contains a dissociable PKA regulatory component, possibly a polypeptide of 42 kDa.
Effect of bradykinin and kininogens in isolated rat kidney vasoconstricted by angiotensin II
Authors: Gardes J. , Baussant T. , Corvol P. , Menard J. , Alhenc-Gelas F.
Published: December 2017

The hemodynamic and endocrine effects of bradykinin and kininogens were investigated using a closed-circuit isolated rat kidney perfused with angiotensin II (ANG II). ANG II induced vasoconstriction, stimulation of urinary kallikrein release, and inhibition of renin secretion. Bradykinin markedly increased renal perfusate flow (RPF) and produced a slight but significant diuresis and natriuresis. The inhibitory effect of ANG II on renin secretion was delayed. Urinary kallikrein secretion was unchanged. The effect of bradykinin was suppressed by the competitive kinin antagonist [DArg,Hyp3,Thi5,8,DPhe7]bradykinin. Kallikrein-sensitive rat high-molecular-weight kininogen produced a progressive rise in renal perfusate flow. Exocrine function and renin and kallikrein secretions were unchanged. Immunoreactive kinins, identified as bradykinin by high-pressure liquid chromatography, were liberated into the perfusate. Perfusate immunoreactive high-molecular-weight kininogen decreased in parallel as a result of consumption. The kalikrein-resistant T-kininogen was not hydrolyzed to release a kinin, had no effect on renal function, and its concentration in the perfusate remained constant. These results suggest that kinin can be produced in the renal circulation from kallikrein-sensitive circulating kininogens and can antagonize the vasoconstrictor effect of ANG II and alter renal hemodynamics. They provide evidence that the kallikrein-kinin system can participate with the renin-angiotensin system in the control of renal blood flow.
Possible endothelial modulation of prostaglandin-stimulated renin release
Authors: Beierwaltes W. H.
Published: December 2017

Studies were run to determine whether the renal microvascular endothelium influences renin release. Blood-free rat renal cortical slices were incubated in a bicarbonate buffer for 60 min and sampled at 30 and 60 min to determine renin concentration and at 60 min for prostaglandin (PG) E2 and I2 (6-keto-PGF1 alpha) synthesis. Stimulation by 10(-6) M melittin of endogenous PGs simultaneously increased renin release, PGE2, and PGI2 synthesis, and all were inhibited by 1.6 x 10(-6) M meclofenamate. Renin release was stimulated with isoproterenol [26.2 +/- 2.4 ng angiotensin I (ANG I) .h-1.mg-1.30 min-1; P less than 0.001], PGI2 (32.3 +/- 7.4 ng ANG I.h-1.mg-1.mg-1.30 min-1; P less than 0.005), and PGE2 (25.7 +/- 2.8 ng ANG I.h-1.mg-1.30 min-1, P less than 0.001). Acetylcholine did not affect basal renin but potentiated the response to PGE2 by 80% (46.0 +/- 5.8 ng ANG I.h-1.mg-1.30 min-1; P less than 0.001). Atropine (10(-7) M) reversed this potentiation. Deendothelialization of renal microvessels with H2O2 eliminated PGI2, but neither PGE2 nor renin release, and reversed acetylcholine-potentiation of PGE2-stimulated renin release as did meclofenamate. Hemoglobin increased PGE2-stimulated renin similarly to acetylcholine. These studies suggest that stimulating the endothelium with acetylcholine results in selective potentiation of PGE2-stimulated renin release, which may be mediated through some cyclooxygenase product and is independent of endothelium-derived relaxing factor. Thus the renal endothelium may influence or modulate renin release.
Prostaglandin E2 inhibits oxygen consumption in rabbit medullary thick ascending limb
Authors: Lear S. , Silva P. , Kelley V. E. , Epstein F. H.
Published: December 2017

The effect of prostaglandin (PG) E2 on transport-dependent oxygen consumption (QO2) of rabbit medullary thick ascending limb (MTAL) cells was studied. Exogenous PGE2, at a concentration of 30 microM, inhibited ouabain-sensitive QO2 by 70%. Addition of either ouabain or bumetanide, after PGE2, further depressed QO2, whereas PGE2 had no effect when added after these transport inhibitors. There was no significant inhibition of QO2 by PGE2 in the absence of either Na or Cl. The QO2 of amphotericin-treated cells was inhibited by the addition of PGE2. Therefore the inhibitory effect of PGE2 was on the transport-dependent moiety of QO2 and was independent of Na entry. Other prostanoids had no significant effect on MTAL QO2. Suspensions of isolated MTAL cells accumulated PGE2 at about one-fifth the rate of outer medullary collecting duct cells. Finally, PGE2 caused an increase in intracellular adenosine 3',5'-cyclic monophosphate levels by approximately 100%. Although the precise mechanism of action is unclear, PGE2, which is synthesized by several cell types in the renal medulla, exerts an inhibitory effect on transport in rabbit MTAL.
Active and passive chloride transport by the rabbit cortical collecting duct
Authors: Wingo C. S.
Published: December 2017

Dietary K intake has been shown to influence solute flux in the cortical collecting duct (CCD). We recently observed active Cl secretion by the CCD when rabbits were fed a K-rich diet. The present studies examined two different methods of K loading (KHCO3 or KCl) on net Cl flux (JNet Cl), active Cl flux (JA Cl), and passive Cl flux (JP Cl) by the rabbit CCD. These two methods of K loading were compared with a low-K diet (control or NaHCO3 diet) that had the same anion composition as the KHCO3 diet (Na for K substitution). In the low-K group there was neither significant net Cl transport nor active Cl secretion. Increasing dietary K content (KHCO3 group) resulted in significant net Cl secretion (JNet Cl = -26.3 +/- 9.3 pmol.mm-1.min-1). Moreover, K secretion was significantly greater (23.8 +/- 4.3 pmol.mm-1.min-1) and transepithelial voltage (VT) was more lumen negative (-14.8 +/- 5.9 mV) compared with the low-K group (P less than 0.05). Consequently, there was both significant passive Cl absorption and significant active Cl secretion. In the KCl group there was significant net Cl absorption (JNet Cl = 17.2 +/- 5.1 pmol.mm-1.min-1, P less than 0.05 vs. low-K diet). However, Na absorption significantly exceeded JNet Cl (JNet Na = 42.0 +/- 7.2 pmol.mm-1.min-1, P less than 0.01), and this group also exhibited the most lumen-negative voltage (VT = -35.4 +/- 5.4 mV).(ABSTRACT TRUNCATED AT 250 WORDS)
Direct evidence for apical Na+:2Cl-:K+ cotransport in macula densa cells
Authors: Lapointe J. Y. , Bell P. D. , Cardinal J.
Published: December 2017

Previous studies by our laboratory indicate that increases in apical NaCl concentration ([NaCl]) depolarize macula densa (MD) cells, although the mechanism for apical NaCl transport was not identified. To determine the pathway for MD apical NaCl transport, we utilized microdissected cortical thick ascending limbs (CTAL) with attached glomeruli and conventional microelectrode techniques. Addition of 50 microM furosemide in the presence of 150 mM NaCl produced a variable hyperpolarization of basolateral membrane voltage (delta Vbl, -14 +/- 8.2 mV, NS P = 0.15, n = 6) and completely blocked the expected repolarization on reducing luminal [NaCl] from 150 to 25 mM. Addition of furosemide in the presence of 25 mM NaCl depolarized Vbl by 22 +/- 6.8 mV (P less than 0.05, n = 6) indicating that the direction of the NaCl transport can be reversed in low luminal [NaCl]. In other studies, luminal concentration of Na or Cl was increased from 25 to 150 mM. Increased [Na] produced a 6.9 +/- 1.2 mV (n = 9) depolarization, whereas Cl addition depolarized Vbl by 8.2 +/- 1.7 mV (n = 5), suggesting that both ions are involved in the NaCl-induced MD depolarization. Removal of K from the luminal perfusate elicited a hyperpolarization of -14 +/- 2.9 mV (n = 9). These results are all consistent with the existence of an apical Na+:2Cl-:K+ transporter that would result in NaCl reabsorption in the presence of 150 mM luminal NaCl but would produce NaCl secretion at low luminal NaCl concentrations.
Role of atrial natriuretic factor in renal adaptation to variation of salt intake in humans
Authors: Dal Canton A. , Romano G. , Conte G. , De Nicola L. , Caglioti A. , Veniero P. , Uccello F. , Andreucci V. E.
Published: December 2017

This study was performed to define the extent to which atrial natriuretic factor (ANF) contributes to upregulate salt excretion in subjects eating a high-salt diet. Eight normal volunteers were first studied at low-salt diet (80 mmol NaCl/day); urinary sodium excretion (UNaV) and plasma ANF (PANF) were measured in the basal condition and during stepwise infusion of human alpha-ANF at 2, 4, 8, and 16 ng.min-1.kg-1. Then the same subjects were shifted to a high-salt diet (400 mmol/day), and UNaV and PANF were measured in the new balance condition. At low-salt diet, UNaV averaged 0.069 meq/min, and PANF averaged 21 pg/ml; infusion of human alpha-ANF raised stepwise both UNaV and PANF (means in meq/min and pg/ml, respectively, were 0.177 and 46, 0.218 and 76, 0.360 and 86, and 0.601 and 182). Infusion of ANF caused a progressive fall of plasma aldosterone and plasma renin activity. Mean UNaV and PANF at high-salt diet were 0.301 meq/min and 35 pg/ml. Thus, by increasing experimentally PANF in a low-salt diet condition to the levels occurring physiologically in a high-salt diet condition, a significant rise in UNaV is evoked, which accounts for approximately 50% of the rise of UNaV that is necessary to balance the increased salt intake.
Effect of acidosis on PTH-dependent renal adenylate cyclase in phosphorus deprivation: role of G proteins
Authors: Bellorin-Font E. , Starosta R. , Milanes C. L. , Lopez C. , Pernalete N. , Weisinger J. , Paz-Martinez V.
Published: December 2017

These studies examine the regulation of adenylate cyclase in renal cortical membranes from phosphate-deprived and phosphate-deprived acidotic dogs. Enzyme stimulation by parathyroid hormone (PTH) was decreased in phosphate deprivation [Vmax 1,578 +/- 169 vs. 2,581 +/- 219 pmol adenosine 3',5'-cyclic monophosphate (cAMP).mg protein-1 x 30 min-1 in controls, P less than 0.01]. Metabolic acidosis further decreased PTH-stimulated activity. Membranes from phosphate-deprived dogs showed a decrease in Gs alpha-content by cholera toxin-dependent ADP-ribosylation (174 +/- 18 arbitrary units vs. 266.4 +/- 13.6 in controls, P less than 0.01). Metabolic acidosis further decreased Gs alpha-content, P less than 0.01. Gi content by pertussis-dependent ADP-ribosylation was also lower in phosphate-deprived and phosphate-deprived acidotic animals. Gs function was examined by its property to protect the catalytic unit from inactivation by N-ethylmaleimide when preincubated with GTP gamma S. In controls, protection of inactivation was 80% of the maximal activity, whereas in phosphate deprivation protection was less than 50%. In conclusion, metabolic acidosis enhances adenylate cyclase resistance to PTH in phosphate deprivation. These alterations are associated with a decrease in the content and function of Gs alpha, suggesting a role of Gs in the renal adaptation to phosphate depletion and acidosis.
Cell volume regulation of rabbit cortical collecting tubule in anisotonic media
Authors: Natke E.
Published: December 2017

Volume regulation of nonperfused rabbit cortical collecting tubules in anisotonic bathing media was examined in vitro. When media osmolality is abruptly increased by 150 mosmol/kgH2O with the addition of NaCl, tubules shrink by 20% but do not volume regulate. However, volume regulatory increase (VRI) is observed when 1 mM butyrate is present in the bathing media or when tubules are pretreated with hypotonic media. When media osmolality is increased, butyrate-treated tubules shrink to 74% of their isotonic control volume. As evidence of volume regulation, butyrate-treated tubules swell while still bathed in hypertonic media, recovering in 30 min 78% of the volume lost due to osmotic shrinkage. The butyrate effect requires external Na+ and is inhibited by amiloride. When media osmolality is lowered to 150 mosmol/kgH2O, nonbutyrate tubules swell before showing typical volume regulatory decrease. When these tubules are returned to isotonic media, they immediately shrink to 78% of control volume before showing evidence of VRI. These results suggest that, under the appropriate conditions, cortical collecting tubules are capable of VRI.
Atrial natriuretic peptide receptors in renal papilla of DOCA-salt hypertensive rats
Authors: Nuglozeh E. , Gauquelin G. , Garcia R. , Tremblay J. , Schiffrin E. L.
Published: December 2017

The receptor for atrial natriuretic peptide (ANP) in the rat renal papilla was characterized pharmacologically. After solubilization and irreversible binding with disuccinimidylsuberate, it was shown on sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) to be made of a single peptide of 125 kDa. The regulation of the renal papillary ANP receptor was studied in deoxycorticosterone acetate (DOCA)-salt hypertensive rats. DOCA-salt rats had suppressed plasma renin activity and increased plasma ANP concentrations (408 +/- 35 vs. 133 +/- 12 pg/ml in uninephrectomized controls, P less than 0.01). The renal papilla was hypertrophied in DOCA-salt hypertensive rats (93 +/- 1 vs. 52 +/- 1 mg, P less than 0.01). The density of ANP sites in the papilla was significantly higher in DOCA-salt rats (141 +/- 31 fmol/papilla) than in controls (34 +/- 8 fmol/papilla, P less than 0.01). Affinity of sites in DOCA-salt rats and controls was similar. The production of guanosine 3',5'-cyclic monophosphate (cGMP) in renal papilla in response to ANP was significantly higher in DOCA-salt rats. In contrast to the renal papillary ANP receptor, acid-washed vascular and glomerular ANP sites were significantly decreased in density in DOCA-salt hypertensive rats. In blood vessels and glomeruli, both the high- and low-molecular mass receptor (as detected on SDS-PAGE under reducing conditions) was proportionately decreased in density in DOCA-salt hypertensive rats. The present results suggest that an increased number of ANP receptors and exaggerated cGMP response to ANP in the renal papilla may underlie the increased natriuretic responsiveness of the kidney to ANP in DOCA-salt hypertensive rats.
Intracoronary veratrine and acute aortic stenosis modify renal responses to hypotension in conscious dogs
Authors: Chen J. S. , Gorman A. J.
Published: December 2017

The present study was undertaken to determine whether intracoronary (left circumflex) veratrine (ICV) infusions and increases in left ventricular (LV) systolic pressure influence renal circulatory and excretory function in chronically instrumented conscious dogs (n = 19). Thirty minutes of ICV infusions decreased arterial pressure by 15-20 mmHg, but heart rate, urine flow, sodium excretion, and free water clearance did not change. Intravenous nitroprusside infusions, which also lowered arterial pressure by 15-20 mmHg, increased heart rate while urine flow, sodium excretion, and free water clearance were significantly decreased. Heart rate and renal excretory function also did not change during a 15- to 20-mmHg decrease in arterial pressure when LV systolic pressure was simultaneously raised to approximately 170 mmHg by ascending aortic occlusion. The topical application of a local anesthetic in the region of the left main coronary artery abolished the Bezold-Jarisch reflex and the attenuation of hypotension-induced salt and water retention and tachycardia by ICV. Renal plasma flow and glomerular filtration rate were not altered during any of the above experimental treatments. These results suggest that in the conscious dog chemical and mechanical stimulation of LV sensory receptors with afferents in the pericoronary region can modulate the neurohumoral reflex control of renal excretory function independent of local filtration effects.
Hypertension and progressive glomerular injury caused by focal glomerular ischemia
Authors: Miller P. L. , Rennke H. G. , Meyer T. W.
Published: December 2017

Sprague-Dawley rats received infusions of 55-microns microspheres (groups 1 and 3) or dextrose (groups 2 and 4) into both renal arteries. Groups 1 and 2 rats were studied over 7 mo. In group 1 rats renal embolization increased the mean arterial pressure (group 1, 140 +/- 4 mmHg; group 2, 118 +/- 2 mmHg) without reducing the glomerular filtration rate (GFR; group 1, 4.69 +/- 0.16 ml/min; group 2, 4.57 +/- 0.22 ml/min). Micropuncture studies showed that systemic hypertension was accompanied by an increase in the glomerular capillary pressure of functioning nephrons in group 1 rats. Morphological studies showed that renal embolization caused both glomerular ischemia (group 1, 11.8 +/- 1.9% of glomeruli; group 2, 0.1 +/- 0.1% of glomeruli) and glomerular segmental sclerosis (group 1, 15.0 +/- 1.0% of glomeruli; group 2, 3.3 +/- 0.2% of glomeruli). Groups 3 and 4 rats were studied over 2 mo. Renal embolization again increased the mean arterial pressure without reducing the GFR in group 3 rats. Morphological studies showed that at 2 mo renal embolization caused glomerular ischemia without glomerular segmental sclerosis. These studies show that focal glomerular ischemia can cause systemic and glomerular capillary hypertension in the absence of a reduction in the GFR. They further show that focal glomerular ischemia can cause progressive sclerotic injury in the remaining, nonischemic portion of the glomerular population.