bluuebunny/crossref_metadata_2025 huggingface dataset:
Serotonin activates phospholipase D in rat mesangial cells
Authors: Kurscheid-Reich D. , Throckmorton D. C. , Rasmussen H.
Published: December 2017

We tested the hypothesis that serotonin activates phospholipase D (PLD) in cultured rat mesangial cells. The formation of phosphatidylethanol (PET) in ethanol was used as a measure of PLD activity. Serotonin [5-hydroxytryptamine (5-HT)] stimulated PET production, with an initial 10-fold increase in PET content within 15–30 s, followed by a decrease in PET to values only sixfold above baseline at 45–60 s. Thereafter, the values increased again at 5 min to a plateau 10-fold above baseline. The decrease in PET values, following the initial increase, was due to metabolism of PET, possibly by a phosphatidic acid phosphohydrolase, which led to a 76% decrease in PET within 1 h. Inhibition of phosphohydrolase with propranolol increased the phosphatidic acid and decreased the 1,2-diacylglycerol (DAG) content of 5-HT-stimulated cells. Finally, exogenous PLD induced mesangial cell proliferation as well as increases in phosphatidic acid, PET, and DAG. We conclude that phosphatidic acid contributes to DAG formation in mesangial cells. Furthermore, we suggest that PLD is involved in 5-HT-mediated mesangial cell proliferation.
Hypertonic NaCl enhances adenosine release and hormonal cAMP production in mouse thick ascending limb
Authors: Baudouin-Legros M. , Badou A. , Paulais M. , Hammet M. , Teulon J.
Published: December 2017

Adenosine 3',5'-cyclic monophosphate (cAMP), accumulated in the presence of adenosine, was measured in medullary portions of mouse thick ascending limbs of Henle's loop, suspended either in classic extracellular buffer or in the presence of added NaCl. Under control conditions (140 mmol/l NaCl), adenosine (< 10(-5) mol/l) and N6-cyclohexyladenosine, an A1 adenosine receptor agonist, inhibit the cAMP accumulation induced by arginine vasopressin (AVP). On the other hand, high concentrations of adenosine and CGS-21680, an A2 adenosine receptor agonist, stimulate cAMP formation. Addition of NaCl (+300 mmol/l) to extracellular buffer stimulates the release of endogenous adenosine. It also enhances A2 receptor-induced cAMP accumulation but suppresses A1 receptor-mediated inhibition of adenylyl cyclase. This hypertonic NaCl medium also potentiates the stimulatory action of AVP on adenylyl cyclase. The modifications of tubular responses to both AVP and A1 and A2 agonists, brought about by hypertonic NaCl, were all inhibited by adenosine deaminase, thereby demonstrating the involvement of endogenous adenosine. Adenosine, the release and the effects of which are modulated by hypertonic NaCl, thus appears to act as an endogenous physiological modulator of kidney medulla function.
Luminal acidification in K-replete OMCDi: inhibition of bicarbonate absorption by K removal and luminal Ba
Authors: Armitage F. E. , Wingo C. S.
Published: December 2017

We have previously demonstrated that significant luminal acidification in the K-replete rabbit inner stripe of the outer medullary collecting duct (OMCDi) occurs via a renal H-K-adenosinetriphosphatase (H-K-ATPase) sensitive to several of the gastric H-K-ATPase inhibitors. To investigate further the mechanism of K-dependent luminal acidification in K-replete OMCDi, we examined the effects of luminal K removal, luminal addition of Ba in the presence and absence of luminal 5.0 nM bafilomycin A1 (BAF), and basolateral addition of Ba on net bicarbonate flux (JtCO2, pmol.mm-1.min-1) and transepithelial voltage (VT, mV). Removal of K from the perfusate inhibited JtCO2 by 74% (13.4 +/- 4.0 for control, 3.5 +/- 1.4 pmol.mm-1.min-1 for experimental, P < 0.05) and was statistically equivalent to the degree of inhibition previously observed under identical experimental conditions by either 10 microM Sch-28080 or 10 microM A-80915A. Approximately 50% inhibition of JtCO2 was observed following luminal application of 2.0 mM Ba2+, and the degree of inhibition was statistically equivalent regardless of whether BAF was present (12.2 +/- 2.7 for control, 6.0 +/- 1.4 pmol.mm-1.min-1 for 2.0 mM Ba2+, P < 0.05; 9.6 +/- 1.2 for control with 5 nM BAF, 5.7 +/- 1.3 pmol.mm-1.min-1 for 2.0 mM Ba2+ with 5 nM BAF, P < 0.05). Additionally, increasing the luminal concentration of Ba2+ from 2.0 to 4.0 mM resulted in no further inhibition of JtCO2 (8.5 +/- 1.7 for control, 3.9 +/- 1.3 pmol.mm-1.min-1 for 4.0 mM Ba2+, P = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Role of renal nerves in natriuresis of L-NMMA infusion in SHR and WKY rats
Authors: Khraibi A. A.
Published: December 2017

The purpose of this study was to determine the role of the renal nerves in the natriuresis and diuresis that is observed with the systemic infusion of a high dose of NG-monomethyl-L-arginine (L-NMMA) to inhibit nitric oxide synthesis in the Okamoto spontaneously hypertensive rat (SHR) and the Wistar-Kyoto (WKY) rat. All rats in this study underwent a unilateral nephrectomy approximately 2 wk prior to the acute experiment. On the day of the acute experiment, renal denervation of the remaining left kidney was performed in one group of SHR (n = 6) and one group of WKY rats (n = 9). Another group of SHR (n = 6) and WKY rats (n = 10) had an innervated kidney. A control clearance period was taken, and then an L-NMMA (15 mg/kg bolus followed by 500 micrograms.kg-1.min-1 continuous infusion) infusion period followed in all four groups of rats. In the innervated SHR and WKY rats, the increases in fractional excretion of sodium (FENa) were 5.11 +/- 0.70 and 3.58 +/- 0.38%, respectively, with the infusion of L-NMMA and were associated with significant increases in fractional excretions of phosphate (FEPi; 18.18 +/- 5.33 and 6.34 +/- 2.29%, respectively), suggesting a reduction in proximal tubule reabsorption. In the SHRs with acute renal denervation, FENa was significantly increased by L-NMMA; however, FENa was significantly reduced (2.03 +/- 0.70%; P < 0.05) in comparison with innervated SHRs and was associated with no increase in FEPi (FEPi = -0.72 +/- 1.23%).(ABSTRACT TRUNCATED AT 250 WORDS)
Comparison of systemic and direct intrarenal angiotensin II blockade on sodium excretion in rats
Authors: Peng Y. , Knox F. G.
Published: December 2017

To dissociate the renal effects from the systemic effects of angiotensin II blockade, the present study was designed to determine the effects of systemic and renal interstitial infusion of the specific angiotensin II (ANG II) receptor antagonist, losartan, on blood pressure and sodium excretion in rats fed a low-, normal, or high-sodium diet. Fractional sodium excretion (FENa) and mean arterial pressure (MAP) were measured in rats before and during systemic infusion of losartan (10 mg/kg) or renal interstitial infusion of losartan (3 mg/kg) by means of a chronically implanted matrix. In rats fed a low- or normal sodium diet, systemic infusion of losartan markedly decreased MAP (delta -21 +/- 2, delta -10 +/- 2 mmHg, respectively; P < 0.05) with an accompanying fall in FENa (delta -0.10 +/- 0.05, delta -0.91 +/- 0.40%, respectively; P < 0.05). In contrast, preferential blockade of renal ANG II with renal interstitial losartan infusion resulted in an increase in FENa (delta 0.13 +/- 0.04, delta 0.95 +/- 0.45%, respectively; P < 0.05) and no significant change in MAP. In rats fed a high-sodium diet, both systemic and renal interstitial infusion of losartan increased FENa (delta 1.90 +/- 0.26, delta 1.40 +/- 0.56%, respectively; P < 0.05). Although systemic infusion of losartan decreased MAP (delta -4.4 +/- 0.6 mmHg, P < 0.05) in rats fed a high-sodium diet, the reduction in MAP was much less than that in rats fed a low- and normal sodium diet.(ABSTRACT TRUNCATED AT 250 WORDS)
Oxytocin as an antidiuretic hormone. I. Concentration dependence of action
Authors: Chou C. L. , DiGiovanni S. R. , Mejia R. , Nielsen S. , Knepper M. A.
Published: December 2017

Circulating concentrations of oxytocin increase to 10-40 pM in rats in response to osmotic stimuli, suggesting that oxytocin could play a role in regulation of water balance. The present studies tested whether oxytocin at such concentrations increases osmotic water permeability (Pf) in isolated perfused terminal inner medullary collecting ducts (IMCD). In IMCD segments from Sprague-Dawley rats, 20 pM oxytocin added to the peritubular bath caused a two- to threefold increase in Pf, whereas 200 pM oxytocin increased Pf by five- to sixfold (n = 8, P < 0.01). IMCD from Brattleboro rats, which manifest central diabetes insipidus, exhibited a 2.8-fold increase in Pf in response to 20 pM oxytocin and a 4.7-fold increase in response to 200 pM oxytocin. However, in Brattleboro rats, the response to 20 pM oxytocin was dependent on prior water restriction of the rats. Immunoblotting showed no change in the expression of the aquaporin-CD water channel in Brattleboro rats in response to water restriction. Nevertheless, immunofluorescence studies of inner medullary tissue from Brattleboro rats revealed a marked redistribution of the aquaporin-CD water channels to a predominantly apical and subapical localization in IMCD cells in response to water restriction, similar to the redistribution seen in response to vasopressin. Mathematical modeling studies revealed that the measured increase in Pf in response to oxytocin is sufficient to generate a concentrated urine. We conclude that oxytocin can function physiologically as an antidiuretic hormone, mimicking the short-term action of vasopressin on water permeability, albeit with somewhat lower potency.
Multiple mechanisms of receptor-G protein signaling specificity
Authors: Raymond J. R.
Published: December 2017

The hormone-receptor-G protein complex transduces extracellular information into intracellular signals that ultimately regulate cellular functions in a highly specific manner. There are hundreds of receptor types that transduce signals through a relatively limited repertoire of heterotrimeric G proteins. Linear models of signaling specificity that require specific and highly selective coupling of hormone to receptor to G protein have proven inadequate to explain how highly particular signals are funneled through the G protein "bottleneck." Recent studies have uncovered a plethora of mechanisms that contribute to signaling specificity. This review focuses on the mechanisms that contribute to specificity in the interactions of receptors with G proteins.
Frequency domain of renal autoregulation in the conscious dog
Authors: Wittmann U. , Nafz B. , Ehmke H. , Kirchheim H. R. , Persson P. B.
Published: December 2017

The dynamic range in which renal blood flow (RBF) autoregulation occurs was determined in eight conscious foxhounds chronically catheterized in the abdominal aorta and implanted with a transit-time flow probe over the renal artery. Sinusoidal driving pressures (amplitude of 10 mmHg) were forced on the renal arterial pressure at different frequencies by a servo-control device, and transfer functions were calculated. Only one frequency range was found below which the gain of the transfer function declined and in which the phase angle increased (n = 8). This indicates the presence of a potent mechanism for renal autoregulation in the examined frequency range between 0.0031 and 0.08 Hz, which buffers changes in blood flow < 0.02 Hz. After furosemide treatment, one indicator for autoregulation (phase shift of transfer function) was significantly blunted at low frequencies (n = 6). Furosemide, however, did not reduce the phase shift to zero, suggesting that some autoregulation still remained in the frequency range between 0.04 and 0.08 Hz. In conclusion, autoregulation of RBF during sinusoidal changes in driving pressure between 0.0031 and 0.02 Hz is mediated by a single mechanism, which can be blocked by the acute administration of furosemide. The residual phase shift between arterial pressure and RBF in the transfer function observed during sinusoidal changes in driving pressure between 0.04 and 0.08 Hz suggests the presence of a second mechanism for RBF autoregulation.
Anion secretion drives fluid secretion by monolayers of cultured human polycystic cells
Authors: Mangoo-Karim R. , Ye M. , Wallace D. P. , Grantham J. J. , Sullivan L. P.
Published: December 2017

We have investigated the hypothesis that active anion transport drives fluid secretion by the cystic epithelium in autosomal dominant polycystic kidney disease (ADPKD). We prepared monolayers of a primary culture derived from cystic tissue removed from ADPKD patients. The monolayers were grown on permeant supports, and fluid secretion was initiated by forskolin. The results were compared with those obtained with monolayers of Madin-Darby canine kidney (MDCK) cells, known to secrete Cl-. In the absence of the agonist, ADPKD monolayers absorbed fluid (0.20 +/- 0.02 microliter.cm surface area-2.h-1). Forskolin reversed this to secretion (0.60 +/- 0.03 microliter.cm-2.h-1). Control MDCK monolayers did not transport fluid in either direction, but forskolin induced secretion (0.48 +/- 0.03 microliter.cm-2.h-1). The electrical properties of the monolayers were monitored in Ussing chambers. Forskolin increased the transepithelial potential difference (Vte) of ADPKD monolayers (-0.9 +/- 0.1 to -1.1 +/- 0.1 mV) and the short-circuit current (Isc) (6.6 +/- 0.7 to 9.2 +/- 0.8 microA/cm2). The transepithelial resistance (Rte) fell (156 +/- 9 to 138 +/- 10 omega.cm2). Similar results were obtained with MDCK monolayers. The polarity of Vte and the direction of the Isc are compatible with the hypothesis that active secretion of anion drives fluid secretion. Basolateral application of the Na-K-2Cl cotransporter, bumetanide, reduced forskolin-stimulated fluid secretion by ADPKD monolayers (0.56 +/- 0.05 to 0.28 +/- 0.03), depolarized Vte, and inhibited Isc without affecting Rte. Apical application of the Cl- channel blocker, diphenylamine-2-carboxylate, also inhibited fluid secretion by ADPKD monolayers (0.65 +/- 0.03 to 0.27 +/- 0.02 microliter.cm-2.h-1).(ABSTRACT TRUNCATED AT 250 WORDS)
Taurine ameliorates chronic streptozocin-induced diabetic nephropathy in rats
Authors: Trachtman H. , Futterweit S. , Maesaka J. , Ma C. , Valderrama E. , Fuchs A. , Tarectecan A. A. , Rao P. S. , Sturman J. A. , Boles T. H. , et al.
Published: December 2017

We examined the effect of two endogenous antioxidant agents, taurine and vitamin E, on renal function in experimental diabetes. Male Sprague-Dawley rats, rendered diabetic with streptozocin (STZ), were assigned to one of the following groups: 1) untreated; 2) insulin treatment with 6 U Ultralente insulin/day in two doses; 3) taurine supplementation by 1% taurine in drinking water; and 4) vitamin E supplementation at 100 IU vitamin E/kg chow. Animals were kept for 52 wk. The survival rate was similar (70-90%) in all groups except vitamin E-treated animals, of which 84% died by 6 mo. At 52 wk, glomerular filtration rate was elevated in untreated and taurine-treated STZ rats compared with normal or insulin-treated diabetic rats. Taurine supplementation reduced total proteinuria and albuminuria by nearly 50%. This treatment also prevented glomerular hypertrophy, preserved immunohistochemical staining for type IV collagen in glomeruli, and diminished glomerulosclerosis and tubulointerstitial fibrosis in diabetic animals. The changes in renal function and structure in taurine-treated diabetic rats were associated with normalization of renal cortical malondialdehyde content, lowering of serum free Fe2+ concentration, and decreased formation of the advanced glycooxidation products, pentosidine, and fluorescence in skin collagen. Administration of the vitamin E-enriched diet exacerbated the nephropathy in STZ-diabetic rats. In addition, vitamin E supplementation increased serum free Fe2+ concentration, enhanced renal lipid peroxidation, and accelerated the accumulation of advanced glycosylation end products (AGEs) in skin collagen. We conclude that administration of taurine, but not vitamin E, to rats with STZ-diabetes ameliorates diabetic nephropathy. The beneficial effect of taurine is related to reduced renal oxidant injury with decreased lipid peroxidation and less accumulation of AGEs within the kidney.
Endothelin receptor mRNA expression in renal medulla identified by in situ RT-PCR
Authors: Chow L. H. , Subramanian S. , Nuovo G. J. , Miller F. , Nord E. P.
Published: December 2017

Three subtypes of endothelin (ET) receptors have been identified by cDNA cloning, namely ET-RA, ET-RB, and ET-RC. In the current study the precise cellular distribution of the ET receptor subtypes in the renal medulla was explored by detecting the corresponding polymerase chain reaction (PCR)-amplified cDNAs by in situ reverse transcription (RT)-PCR. The PCR-amplified cDNAs were detected either by direct incorporation using digoxigenin-dUTP (dig-dUTP) as a nucleotide substrate in the PCR reaction or by in situ hybridization with the dig-dUTP-labeled probe. ET-RB mRNA was detected exclusively in the epithelial cells of the inner and outer medullary collecting duct. In contrast, ET-RA message was observed primarily in interstitial cells and pericytes of the vasae rectae in the outer and inner medulla. Southern blot analysis of PCR-amplified cDNAs reverse transcribed from extracted RNA of rat renal medulla confirmed the specificity of the RT-PCR products. ET-RC mRNA was not detected. We conclude that ET-RB is the major ET receptor found in rat renal medulla and is expressed exclusively on inner medullary collecting duct cells. The pattern of ET receptor mRNA expression described suggests different physiological actions for ET on the diverse cellular structures of the renal medulla.
Selective A1 adenosine receptor antagonism augments beta-adrenergic-induced renin release in vivo
Authors: Pfeifer C. A. , Suzuki F. , Jackson E. K.
Published: December 2017

This study determines, in vivo, whether endogenous adenosine/A1 receptor interactions at juxtaglomerular cells restrain the release of renin induced by receptor-mediated activation of the adenosine 3',5'–cyclic monophosphate pathway and whether endogenous adenosine/A2 receptor interactions diminish this restraining response. The following four pharmacological probes were employed: 1) 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) and 2) FK-453, both selective A1 receptor antagonists; 3) FR-113452, a nearly inactive enantiomer of FK-453; and 4) KF-17837, a selective A2 receptor blocker. Adult Sprague-Dawley rats were prepared (adrenalectomized, renal denervated, uninephrectomized, and treated with indomethacin, aldosterone, and hydrocortisone) to minimize endogenous stimulation of renin release and received either vehicle (control group) or one of the four drugs. Intrarenal infusions of isoproterenol (3, 30, and 100 ng.kg-1.min-1) caused dose-related increases in plasma renin activity (PRA). This PRA response was significantly augmented in the groups receiving DPCPX (P = 0.0010) or FK-453 (P = 0.0001) but was not altered in the groups treated with FR-113452 (P = 0.3422) or KF-17837 (P = 0.2155). Systemic and renal hemodynamics and renal electrolyte excretions were monitored and could not account for the PRA augmentation caused by the A1 antagonists. This study clearly demonstrates that endogenous adenosine acts on the A1 receptor to restrain the renin release induced by activation of intrarenal beta-adrenoceptors and is not counteracted by endogenous activation of the A2 receptor.
Expression of endothelins 1 and 3 in the rat kidney
Authors: Firth J. D. , Schricker K. , Ratcliffe P. J. , Kurtz A.
Published: December 2017

Endothelins (ETs) 1 and 3 are expressed in the rat kidney, but the factors that regulate this expression remain unknown. To try to understand what these might be, we have measured the renal levels of ET-1 and ET-3 mRNAs by the ribonuclease protection-assay technique after a number of clearly defined renal/hemodynamic insults. 1) Six hours after the induction of hemorrhagic anemia and hypotension, there was a threefold increase in ET-1 mRNA and a simultaneous threefold decrease in ET-3 mRNA. This indicates that, in this situation, these two ET isoforms are differentially controlled and emphasizes the need for assay techniques capable of distinguishing between them. 2) One day after application of a 0.2-mm clip to the left renal artery, there was a > 2.5-fold induction of ET-1 mRNA in that kidney, which persisted for 10 days. A smaller rise in ET-1 mRNA was seen in the contralateral organ. After 2 days, ET-3 mRNA levels were reduced by approximately 50% in the clipped organ. Both ramipril (an angiotensin-converting enzyme inhibitor, 7.5 mg/kg daily) and bosentan (a nonselective ET receptor antagonist, 100 mg/kg daily) substantially reduced the elevation in ET-1 mRNA seen in the clipped kidney after 2 days, suggesting that the generation of angiotensin II and the action of ET itself are involved in the mechanism by which clipping stimulates ET-1 expression. By contrast, ramipril, but not bosentan, prevented the reduction in ET-3 mRNA levels. 3) Renal denervation, dietary salt restriction, or diuretic treatment (furosemide) did not alter renal expression of ET-1 or ET-3.(ABSTRACT TRUNCATED AT 250 WORDS)
DARPP-32 promoter directs transgene expression to renal thick ascending limb of loop of Henle
Authors: Blau S. , Daly L. , Fienberg A. , Teitelman G. , Ehrlich M. E.
Published: December 2017

DARPP-32, a dopamine- and adenosine 3',5'-cyclic monophosphate (cAMP)-regulated inhibitor of protein phosphatase-1, is highly colocalized with neuronal and nonneuronal D1-type receptors. DARPP-32 concentration is enriched in the renal outer medulla and in the medium-size spiny neurons of the brain. In the ascending limb of the loop of Henle, DARPP-32 is phosphorylated following stimulation by dopamine and other first messengers, and in this form inhibits the activity of the Na(+)-K(+)-adenosinetriphosphatase pump. For functional analysis of the DARPP-32 promoter in the kidney, we characterized the murine gene. There are two groups of transcription start sites utilized in the brain, but the proximal set appears to be preferentially used in the kidney. In four of four lines of mice carrying a DARPP-32/lacZ transgene with 2.1 kb of 5'-flanking DNA, adult kidney lacZ transgene expression mimicked that of endogenous DARPP-32. There was no ectopic expression in peripheral organs. We conclude that the sequences necessary for direction of DARPP-32 expression to the medullary thick ascending limb are contained within this 2.1-kb fragment.
Cross-linked hemoglobin increases fractional reabsorption and GFR in hypoxic isolated perfused rat kidneys
Authors: Baines A. D. , Christoff B. , Wicks D. , Wiffen D. , Pliura D.
Published: December 2017

We compared the ability of human red blood cells (RBC) and a cell-free oxygen carrier to maintain isolated perfused kidney function under moderately hypoxic conditions. Recirculating perfusate was gassed initially with 93% air-7% CO2, and, after 30 min, the gas was changed to 12 O2-7 CO2-81% N2. Oxygen content of the perfusate was increased with RBC (30 g/l Hbg) or highly purified human hemoglobin Ao (HbAo) polymerized with O-raffinose (o-R-poly-Hb, 30 g/l Hbg). For comparison, kidneys were perfused with 60 g/l of bovine serum albumin (BSA) alone. The effects of unmodified hemoglobin were examined by adding 5 g/l of nonpolymerized HbAo to the BSA perfusate after 20 min. The effect of increasing oxygen delivery without hemoglobin was examined by switching to 93% O2 after 20 min during some BSA perfusions (BSA-HiO2). Vascular resistance decreased progressively in o-R-poly-Hb- and BSA-HiO2-perfused kidneys but remained constant in other experiments. Nitro-L-arginine methyl ester (L-NAME) prevented vasodilation and increased the filtration fraction of o-R-poly-Hb-perfused kidneys with no change in other functions. L-NAME also prevented the formation of methemoglobin. After a 70-min perfusion with BSA, Na reabsorption was 82 +/- 3% (means +/- SD), and inulin clearance [glomerular filtration rate (GFR)] was 0.66 +/- 0.33 ml.min-1.g-1. RBC increased reabsorption to 95% (85-98%) (median, 25th-75th percentile) but did not alter GFR (0.52 +/- 0.26 ml.min-1.g-1). o-R-poly-Hb increased Na reabsorption proportionately more than GFR, so that, while GFR was doubled to 1.04 +/- 0.40 ml.min-1.g-1, Na reabsorption increased to 98% (92-99.5%). HbAo increased GFR to 1.07 +/- 0.44 ml.min-1.g-1 and increased reabsorption to 89 +/- 6%.(ABSTRACT TRUNCATED AT 250 WORDS)
Developmental regulation of chloride/formate exchange in guinea pig proximal tubules
Authors: Guillery E. N. , Huss D. J.
Published: December 2017

There is a marked decrease in renal NaCl excretion immediately following birth. To test the hypothesis that parallel upregulation of the proximal tubule apical membrane Na+/H+ and Cl-/formate exchangers contributes to this postnatal adaptation, we measured exchanger activities in brush-border membrane vesicles from near-term fetal, 3- to 5-day-old, and adult guinea pigs. Uptake of 36Cl- was measured in the presence of an outwardly directed formate gradient and an inwardly directed proton gradient. In other experiments, 22Na+ uptake was measured in the presence of an outwardly directed proton gradient. 36Cl- uptake was inhibitable by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and furosemide, and 22Na+ uptake was inhibitable by amiloride. Maximal uptakes of both 36Cl- and 22Na+ exceeded 2-h equilibration values in vesicles from newborn and adult guinea pigs, suggesting transporter-mediated uptake. Such overshoots were not seen with the vesicles from fetuses. Compared with vesicles from fetuses, the initial velocity of formate-driven 36Cl- uptake was 73% greater in vesicles from newborns and 65% greater in vesicles from adults. These results demonstrate parallel upregulation of proximal tubule Na+/H+ and Cl-/formate exchanger activities immediately after birth. This parallel upregulation may be important in mediating the postnatal decrease in renal NaCl excretion.
Kallikrein excretion in Dahl salt-sensitive and salt-resistant rats with native and transplanted kidneys
Authors: Churchill P. C. , Churchill M. C. , Bidani A. K. , Rabito S. F.
Published: December 2017

Urinary kallikrein excretion is decreased in Dahl salt-sensitive (S) vs. salt-resistant (R) rats, and several lines of reasoning suggest not only that decreased kallikrein excretion is a marker for salt-sensitive hypertension but also that kallikrein might play a pathogenic role. Because previous cross-transplantation studies have demonstrated that the kidney's genotype plays a role in determining the blood pressure of the recipient in Dahl S and R rats, the present experiments were designed to determine whether both blood pressure and urinary kallikrein excretion "traveled with the kidney" in transplantation. The Rapp strains of S and R were maintained on a low- NaCl (0.13%) diet until kidney transplantation (bilaterally nephrectomized recipients), at which time the diet was switched to high NaCl (7.8%). Sixteen days later, blood pressures (tail-cuff plethysmography) of the cross-transplant groups (R/S and S/R, indicating kidney genotype/recipient genotype) were nearly identical to each other and intermediate between the blood pressures of the control groups with transplanted kidneys (R/R and S/S). Renal function studies, performed on anesthetized rats 17 days after surgery, demonstrated that R kidneys had higher glomerular filtration rates, renal plasma flows, and urinary kallikrein excretion rates than S kidneys. These differences tended to be preserved in the cross-transplant groups, and therefore they must be genetically determined intrinsic differences between R and S kidneys. This was especially striking with respect to urinary kallikrein excretion. The rank order of urinary kallikrein excretion was R/R = R/S > S/R = S/S, which implies that it is completely determined by the genotype of the kidney.(ABSTRACT TRUNCATED AT 250 WORDS)
Role of NF-kappa B in the regulation of inducible nitric oxide synthase in an MTAL cell line
Authors: Kone B. C. , Schwobel J. , Turner P. , Mohaupt M. G. , Cangro C. B.
Published: December 2017

The effects of cytokines, lipopolysaccharide (LPS), 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP), and pyrrolidine dithiocarbamate (PDTC), an inhibitor of nuclear factor kappa B (NF-kappa B) activation, on inducible nitric oxide synthase (iNOS) expression were studied in the medullary thick ascending limb of Henle's loop cell line ST-1. LPS + interferon-gamma (IF-gamma) promoted a time-dependent increase in nitrite (a NO metabolite) and iNOS mRNA and the appearance of NF-kappa B p50 and p65 in nuclear protein extracts. Actinomycin D but not cycloheximide prevented the LPS + IF-gamma induction of iNOS mRNA and NO synthesis, indicating that iNOS transcriptional activation by LPS + IF-gamma does not require newly synthesized proteins. PDTC inhibited the LPS + IF-gamma induction of NO, iNOS mRNA, and the appearance of NF-kappa B in nuclear protein extracts, suggesting that NF-kappa B mobilization and trans-activation of the iNOS gene mediates this induction. In contrast to other cell types, cycloheximide did not alter iNOS mRNA stability, and 8-BrcAMP did not alter basal or LPS+IF-gamma induced NO production in ST-1 cells.
Role of bradykinin B2 receptors in the developmental changes of renal hemodynamics in the neonatal rat
Authors: el-Dahr S. S. , Yosipiv I. V. , Lewis L. , Mitchell K. D.
Published: December 2017

The present study was performed to evaluate the role of bradykinin, acting via B2 receptors, in the developmental rise in renal blood flow (RBF) and glomerular filtration rate (GFR) in the rat. Newborn rats were chronically treated from birth with the kinin B2 receptor antagonist HOE-140 (600 micrograms/kg sc, every 12 h, n = 9) or 0.9% saline (n = 7). Weanling rats (mean age 23 days) were anesthetized with pentobarbital sodium (50 mg/kg ip) for measurements of mean arterial pressure (MAP), GFR, and renal plasma flow estimated from p-aminohippurate (PAH) clearance (ERPF). Outer cortical RBF (OCBF) was measured by laser-Doppler flowmetry. Baseline MAP was similar in HOE-140- and saline-treated rats (96 +/- 4 vs. 97 +/- 4 mmHg). Also, baseline GFR (0.65 +/- 0.05 vs. 0.52 +/- 0.08 ml.min-1.g-1) and ERPF (1.6 +/- 0.2 vs. 1.3 +/- 0.1 ml.min-1.g-1) were not different in HOE-140- and saline-treated rats, respectively. Intravenous infusion of 200 ng bradykinin did not change MAP or OCBF in HOE-140 rats but decreased MAP (-29 +/- 3%, P < 0.05) and OCBF (-20 +/- 2%, P < 0.05) in controls. Intravenous infusion of 25 ng angiotensin II increased MAP equally in both groups (-32 +/- 4%) and caused a similar reduction in OCBF (-37 +/- 14 vs. -46 +/- 5%). The angiotensin type 1 (AT1) receptor antagonist losartan (10 mg/kg iv) decreased MAP equally in both groups (-22 +/- 2%). However, AT1 blockade increased ERPF to 3.1 +/- 0.8 ml.min-1.g-1 (P < 0.05 vs. baseline) in saline but not in HOE-140 rats (1.9 +/- 0.4 ml.min-1.g-1). Kidney renin mRNA and angiotensin II contents were not different in HOE-140 vs. saline groups. The present findings indicate that bradykinin is not a primary mediator of the maturational rise in RBF or GFR in the rat. However, the data suggest that under control conditions, angiotensin II, acting via AT1 receptors, counteracts the renal vasodilatory effects of endogenous bradykinin in the developing kidney.
Parallel regulation of constitutive NO synthase and renin at JGA of rat kidney under various stimuli
Authors: Bosse H. M. , Bohm R. , Resch S. , Bachmann S.
Published: December 2017

Four chronic experiments were performed to assess changes in the activity and gene expression of type I nitric oxide synthase (NOS) at the macula densa (MD) and of renin expression and immunoreactivity (IR) at the juxtaglomerular apparatus (JGA) of rat kidney, as follows: 1) two-kidney, one-clip Goldblatt hypertension (2K1C, for 3 and 40 days; sham operation for controls), 2) furosemide treatment (150 mg/kg-1.day-1 ip for 5 days), 3) chronic low-salt diet (0.02%) vs. high-salt diet (3%; both for 11 days), and 4) chronic blockade of NOS by nitro-L-arginine methyl ester (L-NAME, 40 mg.kg-1.day-1 for 2 mo). NOS and renin gene expression, NOS enzyme activity and renin IR were semiquantitatively evaluated with histochemical methods (NADPH diaphorase, in situ hybridization, immunohistochemistry). In 2K1C, marked increases were induced in NOS and renin in the ischemic vs. contralateral kidneys both after 3 and 40 days, respectively (P < 0.05). Related to controls, significant increases in the ischemic kidney were encountered after 3 and 40 days, whereas contralateral suppression of NOS and renin was found only after 40 days. Furosemide treatment resulted in a marked increase of both NOS and renin levels compared with controls (P < 0.05). Salt restriction induced a significant elevation of NOS levels compared with salt loading (P < 0.05), whereas only minor changes were evident in renin levels. L-NAME treatment resulted in a moderate reduction of NOS activity (not significant), whereas renin levels were markedly reduced (P < 0.05). These results show that NOS activity and gene expression are inversely related to chronic changes in renal perfusion, salt balance, and salt transport at the distal tubule in parallel with the known response of renin to these changes. Inhibition of NOS decreases renin levels at the JGA. The histochemical findings support previous concepts that MD-derived NO is involved in the control of renin synthesis.
Nitric oxide and prostaglandins are involved in the macula densa control of the renin system
Authors: Schricker K. , Hamann M. , Kurtz A.
Published: December 2017

This study sought to examine the involvement of prostaglandins and of nitric oxide (NO) in the macula densa-dependent activation of the renin system in vivo. For this purpose, male Sprague-Dawley rats were chronically infused with furosemide (12 mg/day) for 6 days to inhibit macula densa salt transport. To inhibit the synthesis of prostaglandins and of NO, animals were injected with indomethacin (2 mg/kg twice daily) and with nitro-L-arginine methyl ester (L-NAME; 40 mg/kg twice daily) for the last 2 days of the experiment, respectively. Furosemide infusion increased plasma renin activity (PRA) from 8.8 +/- 1.4 to 41 +/- 5.2 ng angiotensin I (ANG I).h-1.ml-1 and renin mRNA levels from 112 +/- 8 of standard to 249 +/- 18% of standard. After treatment with indomethacin, the furosemide-induced increases in renin mRNA levels was attenuated to 190 +/- 11% of standard. After injections of L-NAME, both the furosemide-induced increases of renin mRNA levels and of PRA were reduced to 126 +/- 14% of standard and 22 +/- 5 ng ANG I.h-1.ml-1, respectively. These findings suggest that activation of renin gene expression by blockade of the macula densa function is dependent on intact NO and prostaglandin formation, whereas for stimulation of renin secretion mainly intact NO formation appears to be necessary.
Polarized distribution of renal natriuretic peptide receptors in normal physiology and ischemia
Authors: Ritter D. , Dean A. D. , Guan Z. H. , Greenwald J. E.
Published: December 2017

The polarized expression of guanylyl cyclase-coupled natriuretic peptide receptors, types A (GC-A) and B (GC-B), was measured in inner medullary collecting ducts (IMCD) of normal and ischemic rat kidneys, as well as in IMCD cells. Exposure of normal rat kidney medulla to an anti-GC-A antibody demonstrated a propensity of receptor staining on the cellular basal membrane. The polarization of GC-A receptors was lost in the ischemic kidney. The maximal binding capacity of 125I-atrial natriuretic factor (ANF) to the basal membrane of the inner medullary cell line mIMCD-K2 was five times greater than that to the apical membrane. ANF or C-type natriuretic peptide (CNP) added to the basal side of cultured cells resulted in guanosine 3',5'-cyclic monophosphate formation that was greater than when applied to the apical side. Depletion of ATP stores in cultured cells was followed by an increase of 125I-ANF binding to apical cellular membranes. Similar results were obtained when receptor guanylyl cyclase activity was assayed. In conclusion, these results suggest that functional GC-A and GC-B receptors are present predominantly on the basal membrane of IMCD. However, depletion of cellular ATP stores such as in ischemia is followed by a partial loss of polarization.
Functional activity of H-K-ATPase in individual cells of OMCD: localization and effect of K+ depletion
Authors: Kuwahara M. , Fu W. J. , Marumo F.
Published: December 2017

Recent studies have indicated the presence of hydrogen-potassium-adenosinetriphosphatase (H-K-ATPase) in the collecting duct. We examined the localization of functional H-K-ATPase activity in individual cells of the outer and inner stripes of outer medullary collecting ducts (OMCDo and OMCDi). Tubules were isolated from control and K(+)-depleted rabbits and perfused in vitro. Intracellular pH (pHi) of principal cells, intercalated cells, and OMCDi cells was monitored by fluorescence ratio imaging using 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF). An intracellular acid load was induced by NH3/NH4 prepulse in extracellular Na(+)-, K(+)-, and HCO3(-)-free condition, and then 5 mM K+ was added to the lumen or the bath in the presence of Ba2+. Functional activity of H-K-ATPase was estimated by the difference in the rates of pHi recovery before and after K+ addition. In the control condition, luminal addition of K+ significantly increased the pHi recovery rate by 1.6 +/- 0.4 and 1.9 +/- 0.4 x 10(-3) pH units/s in intercalated calls and OMCDi cells, respectively, but not in principal cells. This K(+)-dependent pHi recovery was inhibited by 63% in intercalated cells and 74% in OMCDi cells in the presence of luminal Sch-28080 (10 microM) but was not affected in the presence of luminal bafilomycin-A1 (10 nM). K+ depletion increased the K(+)-dependent pHi recovery to 2.3-fold in intercalated cells and 2.6-fold in OMCDi cells. By contrast, K(+)-dependent pHi recovery was not detected in the basolateral membrane of any cell types in either the control or the K(+)-depleted condition. These results provide functional evidence that H-K-ATPase is distributed in the luminal membrane of intercalated cells and OMCDi cells and that this ATPase is activated by K+ depletion, suggesting the contribution of intercalated cells and OMCDi cells to K+ conservation in rabbit OMCD.
Antibody and complement reduce renal hemodynamic function in isolated perfused rat kidney
Authors: Jocks T. , Zahner G. , Helmchen U. , Kneissler U. , Stahl R. A.
Published: December 2017

To evaluate the effect of antibody and complement on renal hemodynamic changes, glomerular injury was induced in isolated perfused kidneys by an anti-thymocyte antibody (ATS) and rat serum (RS). Glomerular filtration rate (GFR), renal vascular resistance (RVR), and renal perfusate flow (RPF) were assessed over an 80-min period. The possible role of thromboxane (Tx) was tested by the application of the Tx synthesis inhibitor UK-38485 and the Tx receptor blocker daltroban. Perfusion of kidneys with ATS and RS significantly reduced GFR at 10 min (control, 501 +/- 111; ATS + RS, 138 +/- 86 ml.g kidney-1.min-1, significance of F = 0.000) after RS. Similarly, RPF (ml.g kidney-1.min-1) fell from 19.2 +/- 1.8 to 6.1 +/- 2.0 (significance of F = 0.000), whereas RVR (mmHg.ml-1.g.min) increased threefold from 5.2 +/- 0.4 to 17.9 +/- 5.0 at 10 min. These changes were ameliorated by the pretreatment of the rats with daltroban and UK-38485. Addition of erythrocytes to the perfusate increased RVR and GFR, whereas RPF decreased compared with cell-free perfused kidneys. ATS and RS in this preparation also decrease GFR and RPF. The hemodynamic alterations appeared without changes in filtration fraction. Compared with untreated, perfused control kidneys, glomerular Tx formation was significantly increased in ATS and RS perfused kidneys. These data demonstrate that antibody and RS induce impairment of renal hemodynamics, which are mediated by increased Tx formation.
Localization of parathyroid hormone/parathyroid hormone-related peptide receptor mRNA in kidney
Authors: Lee K. , Brown D. , Urena P. , Ardaillou N. , Ardaillou R. , Deeds J. , Segre G. V.
Published: December 2017

In kidney, parathyroid hormone (PTH) exerts differential distal effects along the nephron. To define cells expressing receptors for PTH in kidney, we localized PTH/ PTH-related peptide (PTH/PTHrP) receptor mRNA in rat kidney by in situ hybridization. PTH/PTHrP receptor mRNA is localized to glomerular podocytes, convoluted and straight proximal tubules, the cortical portion of thick ascending limbs, and distal convoluted tubules, but was not detected in the thin limb of Henle's loop or in collecting ducts. Northern blot analysis showed that cultured human glomerular podocytes express a unique 4.0-kb PTH/PTHrP receptor transcript but do not express detectable levels of the common approximately 2.4-kb transcript found in whole kidney and in many other tissues. Whereas the tubular localization of PTH/PTHrP receptor mRNA coincides well with previously known sites of PTH action, the intense expression and the unique size of the PTH/PTHrP receptor transcript in glomerular podocytes suggest that PTH and/or PTHrP may play a role(s) in glomerular function.
Adhesion of calcium oxalate monohydrate crystals to anionic sites on the surface of renal epithelial cells
Authors: Lieske J. C. , Leonard R. , Swift H. , Toback F. G.
Published: December 2017

Adhesion of microcrystals to the apical surface of renal tubular cells could be a critical step in the formation of kidney stones. The role of membrane surface charge as a determinant of the interaction between renal epithelial cells (BSC-1 line) and the most common crystal in kidney stones, calcium oxalate monohydrate (COM), was studied in a tissue culture model system. Adhesion of COM crystals to cells was blocked by cationized ferritin. Other cations that bind to cells including cetylpyridinium chloride and polylysine, as well as cationic dyes such as Alcian blue, also inhibited adhesion of COM crystals, but not all polycations shared this effect. Specific lectins including Triticum vulgaris (wheat germ agglutinin) blocked crystal binding to the cells. Furthermore, treatment of cells with neuraminidase inhibited binding of crystals. Therefore, anionic cell surface sialic acid residues appear to function as COM crystal receptors that can be blocked by specific cations or lectins. In vivo, alterations in the structure, function, quantity, or availability of these anionic cell surface molecules could lead to crystal retention and formation of renal calculi.
Altered EGF expression and thyroxine metabolism in kidneys following acute ischemic injury in rat
Authors: Rogers S. A. , Miller S. B. , Hammerman M. R.
Published: December 2017

To define the relationship between renal epidermal growth factor (EGF) expression and thyroid hormones in acute renal failure, we performed an analysis of the renal thyroid hormone-EGF axis following acute ischemic renal injury in rats. Levels of mature EGF extractable from kidney were elevated 24 h postinjury, and levels of membrane-associated EGF precursor were reduced. Administration of triodothyronine (T3) to rats, either prior to or immediately following the induction of injury, did not further increase levels of extractable EGF. Levels of EGF mRNA in kidneys were reduced 24 h following acute ischemic damage and not affected by administration of T3. Enhanced production of mature EGF from EGF precursor occurred in membranes isolated from kidneys of rats 24 h postinjury compared with production in membranes from kidneys of normal rats. In addition, levels of thyroxine 5'-deiodinase activity in renal membranes were increased 24 h following injury. Levels of circulating total thyroxine (T4), free T4, and free T3 were reduced postischemic injury. Total T3 was unchanged. The administration of T3 to normal rats increased renal 5'-deiodinase activity and EGF precursor cleavage. Administration of propylthiouracil to rats inhibited renal 5'-deiodinase activity and prevented the increase in extractable EGF postischemic injury. We conclude that the increase in levels of mature EGF extractable from kidneys of rats postischemic injury results from enhanced activity of the serine protease that cleaves the EGF precursor. This activity may be stimulated by T3 produced in kidney. These alterations in renal T4 metabolism and EGF expression could serve to facilitate recovery of renal function following ischemia.
Regional and segmental localization of AE2 anion exchanger mRNA and protein in rat kidney
Authors: Brosius F. C. , Nguyen K. , Stuart-Tilley A. K. , Haller C. , Briggs J. P. , Alper S. L.
Published: December 2017

Pages F461–F468: F. C. Brosius III, K. Nguyen, A. K. Stuart-Tilley, C. Haller, J. P. Briggs, and S. L. Alper. “Regional and segmental localization of AE2 anion exchanger mRNA and protein in rat kidney.” The last portion of the legend to Fig. 6 (p. F465) should read as follows: “B: immunoblot of mouse kidney microsomes prepared with high concentrations of protease inhibitors. All lanes were loaded with 25 μg protein from medulla ( lanes 1 and 4), cortex ( lanes 2 and 5), and whole kidney ( lanes 3 and 6). Blots were visualized with ECL.” Also, in the accompanying section of text in the results (p. 465, column 2), at the paragraph beginning “Membranes prepared...”, the second sentence should read as follows: “Maximal levels of 170-kDa AE2 polypeptide were present in medulla (Fig. 6B, lane 1), whereas cortex (Fig. 6B, lane 2) contained lower levels of AE2.”
Spontaneous blood pressure fluctuations and renal blood flow dynamics
Authors: Cupples W. A. , Novak P. , Novak V. , Salevsky F. C.
Published: December 2017

Two mechanisms operating at 0.03-0.05 and 0.1-0.2 Hz are involved in autoregulation of renal blood flow (RBF). To examine the behavior of the faster system, the response of RBF to spontaneous fluctuations of arterial pressure was assessed in Sprague-Dawley rats anesthetized by isoflurane or halothane. During halothane anesthesia, autonomous oscillation of total RBF was observed at 0.10-0.15 Hz, and normalized admittance gain became negative at 0.11 +/- 0.01 Hz. During isoflurane anesthesia, there was autonomous power in blood flow in a broad peak between 0.15 and 0.25 Hz, and gain became negative at 0.15 +/- 0.01 Hz. Increasing inspired isoflurane concentration from 1.4 +/- 0.1% to 2.2 +/- 0.1% reduced pressure by 22 +/- 2 mmHg but did not alter blood flow or the transfer function, indicating that the operating frequency was not changed. In another experiment, changing from isoflurane to halothane increased peak power in the autonomous blood flow oscillation fivefold and reduced its frequency from 0.18 +/- 0.01 to 0.14 +/- 0.01 Hz. Gain became negative at a higher frequency (0.16 +/- 0.01 Hz) during isoflurane than halothane anesthesia (0.12 +/- 0.01 Hz). The results show that the 0.1–0.2 Hz system is reliably detected under unforced conditions and provides modest attenuation of pressure fluctuations at < or = 0.1 Hz. Its operating frequency under isoflurane anesthesia is consistent with previous estimates from barbiturate-anesthetized rats, whereas it operates significantly slower under halothane anesthesia.