Impaired diluting capacity of the thick ascending limb during loop bicarbonate and nitrate perfusion in vivo

1984 ◽  
Vol 62 (11) ◽  
pp. 1416-1422 ◽  
Author(s):  
Hans-Ulrich Gutsche ◽  
Linda N. Peterson ◽  
Karl-Heinz Sauerwald ◽  
David Z. Levine
Keyword(s):  
Animal Studies ◽  
Urine Concentration ◽  
Thick Ascending Limb ◽  
Distal Nephron ◽  
Nacl Transport ◽  
Minimum Concentration ◽  
Bicarbonate Solutions ◽  
Flow Experiments ◽  
Stop Flow

Previous whole animal studies have indicated that when nitrate or bicarbonate is substituted for chloride, renal concentrating defects can be demonstrated. It has been proposed that function of the "distal nephron" or thick ascending limb may be impaired when chloride is replaced by other anions. To examine this proposal, microstop-flow experiments were performed in rats in which loops were perfused with solutions containing 110 mM NaCl, NaHCO3, or NaNO3. Solute reabsorption by the thick ascending limb was assessed by measuring the minimum conductivity of fluid emerging from the loop following intervals of stop-flow. Thick ascending limb solute transport was impaired in loops perfused with HCO3 or NO3 evidenced by the marked increase in solute remaining in the loop after 60 s of stop-flow. The calculated corresponding sodium concentrations were in the range of 17–24 mM Na for the NaCl perfusion, 57–88 mM Na for the NaHCO3 perfusion, and 57–69 mM Na for the NaNO3 perfusion. Clearly, the minimum concentration achieved with NaCl was approximately one-third of that reached with the nitrate or bicarbonate solutions. These results indicate that when chloride-poor solutions reach the thick ascending limb, an important impairment of diluting capacity is demonstrable in vivo in the rat. The present studies, therefore, provide an important link between recent information regarding the mechanism of NaCl transport in the thick ascending limb and older whole animal studies suggesting an important role for distal chloride delivery in urine concentration.

Endothelin inhibits thick ascending limb chloride flux via ETB receptor-mediated NO release

2000 ◽  
Vol 279 (2) ◽  
pp. F326-F333 ◽  
Author(s):  
Craig F. Plato ◽  
David M. Pollock ◽  
Jeffrey L. Garvin
Keyword(s):  
Intracellular Calcium ◽  
Chloride Transport ◽  
Inhibitory Effect ◽  
Thick Ascending Limb ◽  
Inhibitory Effects ◽  
Chloride Flux ◽  
Nacl Transport ◽  
No Release ◽  
Bq 610

Endothelin-1 (ET-1) inhibits transport in various nephron segments, and the thick ascending limb of the loop of Henle (TALH) expresses ET-1 receptors. In many tissues, activation of ETB receptors stimulates release of NO, and we recently reported that endogenous NO inhibits TALH chloride flux ( J Cl). However, the relationship between ET-1 and NO in the control of nephron transport has not been extensively studied. We hypothesized that ET-1 decreases NaCl transport by cortical TALHs through activation of ETBreceptors and release of NO. Exogenous ET-1 (1 nM) decreased J Cl from 118.3 ± 15.0 to 62.7 ± 13.6 pmol · mm−1 · min−1 (48.3 ± 8.2% reduction), whereas removal of ET-1 increased J Cl in a separate group of tubules from 87.6 ± 10.7 to 115.2 ± 10.3 pmol · mm−1 · min−1 (34.5 ± 6.2% increase). To determine whether NO mediates the inhibitory effects of ET-1 on J Cl, we examined the effect of inhibiting of NO synthase (NOS) with N G-nitro-l-arginine methyl ester (l-NAME) on ET-1-induced changes in J Cl. l-NAME (5 mM) completely prevented the ET-1-induced reduction in J Cl, whereas d-NAME did not. l-NAME alone had no effect on J Cl. These data suggest that the effects of ET-1 are mediated by NO. Blockade of ETBreceptors with BQ-788 prevented the inhibitory effects of 1 nM ET-1. Activation of ETB receptors with sarafotoxin S6c mimicked the inhibitory effect of ET-1 on J Cl (from 120.7 ± 12.6 to 75.4 ± 13.3 pmol · mm−1 · min−1). In contrast, ETA receptor antagonism with BQ-610 did not prevent ET-1-mediated inhibition of TALH J Cl (from 96.5 ± 10.4 to 69.5 ± 8.6 pmol · mm−1 · min−1). Endothelin increased intracellular calcium from 96.9 ± 14.0 to 191.4 ± 11.9 nM, an increase of 110.8 ± 26.1%. We conclude that exogenous endothelin indirectly decreases TALH J Cl by activating ETB receptors, increasing intracellular calcium concentration, and stimulating NO release. These data suggest that endothelin acts as a physiological regulator of TALH NO synthesis, thus inhibiting chloride transport and contributing to the natriuretic effects of ET-1 observed in vivo.

Effect of calcitonin on urine concentration in the rat

1983 ◽  
Vol 244 (4) ◽  
pp. F432-F435 ◽  
Author(s):  
S. Carney ◽  
T. Morgan ◽  
C. Ray ◽  
L. Thompson
Keyword(s):  
Water Permeability ◽  
Partial Agonist ◽  
Collecting Duct ◽  
Free Water ◽  
Urine Concentration ◽  
Distal Nephron ◽  
Free Water Clearance ◽  
Normal Increase

Because mammalian distal nephron segments with both calcitonin- and antidiuretic hormone- (ADH) sensitive adenylate cyclase activity have been described, in vivo and in vitro experiments were performed to study the effect of calcitonin on rat distal nephron water permeability. Calcitonin 1 and 0.1 U/ml, but not 0.01 U/ml, significantly increased the diffusional water permeability in the isolated papillary collecting duct by 15 and 11%, respectively. However, this effect was small when compared with a 68% increase with a supramaximal concentration of ADH (from 4.0 +/- 0.3 to 6.7 +/- 0.9 microns/s; n = 6, P less than 0.01). The normal increase in water permeability with increasing concentration of ADH (0.02 and 0.2 mU/ml) was depressed by the previous addition of calcitonin (1 U/ml) to the bath but was unaltered with the supramaximal ADH concentration (2 mU/ml). Verapamil, a compound that antagonizes cellular calcium entry, did not alter the effect of calcitonin on diffusional water permeability. Calcitonin in concentrations of 0.05, 0.5, and 5 U/ml produced a significant reduction in urine flow and free water clearance. Pretreatment with calcitonin in these concentrations inhibited the antidiuretic action of ADH. These studies suggest that calcitonin acts as a partial agonist to ADH within the distal nephron. It is unclear whether such an action represents a physiological or a pharmacological effect.

scholarly journals Effects of NKCC2 isoform regulation on NaCl transport in thick ascending limb and macula densa: a modeling study

2014 ◽  
Vol 307 (2) ◽  
pp. F137-F146 ◽  
Author(s):  
Aurélie Edwards ◽  
Hayo Castrop ◽  
Kamel Laghmani ◽  
Volker Vallon ◽  
Anita T. Layton
Keyword(s):  
Cell Model ◽  
Basolateral Membrane ◽  
Macula Densa ◽  
Tubuloglomerular Feedback ◽  
Thick Ascending Limb ◽  
Differential Splicing ◽  
Dietary Salt ◽  
Nacl Transport ◽  
Low Salt

This study aims to understand the extent to which modulation of the Na+-K+-2Cl− cotransporter NKCC2 differential splicing affects NaCl delivery to the macula densa. NaCl absorption by the thick ascending limb and macula densa cells is mediated by apical NKCC2. A recent study has indicated that differential splicing of NKCC2 is modulated by dietary salt (Schieβl IM, Rosenauer A, Kattler V, Minuth WW, Oppermann M, Castrop H. Am J Physiol Renal Physiol 305: F1139–F1148, 2013). Given the markedly different ion affinities of its splice variants, modulation of NKCC2 differential splicing is believed to impact NaCl reabsorption. To assess the validity of that hypothesis, we have developed a mathematical model of macula densa cell transport and incorporated that cell model into a previously applied model of the thick ascending limb (Weinstein AM, Krahn TA. Am J Physiol Renal Physiol 298: F525–F542, 2010). The macula densa model predicts a 27.4- and 13.1-mV depolarization of the basolateral membrane [as a surrogate for activation of tubuloglomerular feedback (TGF)] when luminal NaCl concentration is increased from 25 to 145 mM or luminal K+ concentration is increased from 1.5 to 3.5 mM, respectively, consistent with experimental measurements. Simulations indicate that with luminal solute concentrations consistent with in vivo conditions near the macula densa, NKCC2 operates near its equilibrium state. Results also suggest that modulation of NKCC2 differential splicing by low salt, which induces a shift from NKCC2-A to NKCC2-B primarily in the cortical thick ascending limb and macula densa cells, significantly enhances salt reabsorption in the thick limb and reduces Na+ and Cl− delivery to the macula densa by 3.7 and 12.5%, respectively. Simulation results also predict that the NKCC2 isoform shift hyperpolarizes the macula densa basolateral cell membrane, which, taken in isolation, may inhibit the release of the TGF signal. However, excessive early distal salt delivery and renal salt loss during a low-salt diet may be prevented by an asymmetric TGF response, which may be more sensitive to flow increases.

Gentamicin Inhibits Ca2+ Channel TPRV5 and Induces Calciuresis Independent of the Calcium-Sensing Receptor-Claudin-14 Pathway

2022 ◽  
pp. ASN.2021030392
Author(s):  
Wouter van Megen ◽  
Megan Beggs ◽  
Sung-Wan An ◽  
Patrícia Ferreira ◽  
Justin Lee ◽  
...  
Keyword(s):  
Patch Clamp ◽  
Hek293 Cells ◽  
Luciferase Reporter ◽  
Thick Ascending Limb ◽  
Wild Type ◽  
Distal Nephron ◽  
Proximal Tubular ◽  
Claudin 14

Background Treatment with the aminoglycoside antibiotic gentamicin can be associated with severe adverse effects, including renal calcium wasting. The underlying mechanism is unknown but it has been proposed to involve activation of the Ca2+-sensing receptor (CaSR) in the thick ascending limb, which would increase expression of claudin-14 (CLDN14) and limit Ca2+ reabsorption. However, no direct evidence for this hypothesis has been presented. Methods We studied the effect of gentamicin in vivo using mouse models with impaired Ca2+ reabsorption in the proximal tubule and the thick ascending limb. We used a Cldn14 promoter luciferase-reporter assay to study CaSR activation and investigated the effect of gentamicin on activity of the distal nephron Ca2+ channel transient potential receptor vanilloid 5 (TPRV5), as determined by patch-clamp in HEK293 cells. Results Gentamicin increased urinary Ca2+ excretion in wild-type mice following acute and chronic administration. This calciuretic effect was unaltered in mice with genetic CaSR overactivation and was present in furosemide-treated animals, whereas the calciuretic effect in Cldn14-/-mice and mice with impaired proximal tubular Ca2+ reabsorption (claudin-2 [CLDN2]-deficient Cldn2-/- mice) was equivalent to that of wild-type mice. In vitro, gentamicin failed to activate the CaSR. In contrast, patch-clamp analysis revealed that gentamicin strongly inhibited rabbit and human TRPV5 activity and that chronic gentamicin administration downregulated distal nephron Ca2+ transporters. Conclusions Gentamicin does not cause hypercalciuria via activation of the CaSR-CLDN14 pathway or by interfering with proximal tubular CLDN2-dependent Ca2+ reabsorption. Instead, gentamicin blocks distal Ca2+ reabsorption by direct inhibition of the Ca2+ channel TRPV5. These findings offer new insights into calcium wasting in patients treated with gentamicin.

Consequences of differential effects of ADH and other peptide hormones on thick ascending limb of mammalian kidney

1991 ◽  
Vol 260 (6) ◽  
pp. R1023-R1035 ◽  
Author(s):  
C. De Rouffignac ◽  
A. Di Stefano ◽  
M. Wittner ◽  
N. Roinel ◽  
J. M. Elalouf
Keyword(s):  
Term Treatment ◽  
Thick Ascending Limb ◽  
Adenylate Cyclase System ◽  
Nacl Transport ◽  
Differential Effects ◽  
Physiological Relevance ◽  
Long Term Treatment ◽  
Nephron Segment

Several hormones stimulate the adenylate cyclase system of the thick ascending limb (TAL). There are, however, some species differences concerning the cyclase sensitivity and the hormonal response in this nephron segment. In the mouse, antidiuretic hormone (ADH), parathyroid hormone, glucagon, calcitonin, and isoproterenol stimulate Na+, Cl-, Mg2+, and Ca2+ transports in the cortical TAL, whereas ADH, glucagon, and isoproterenol stimulate NaCl transport only in the medullary TAL. Many of these effects are different from those previously described for the corresponding segments of the rabbit nephron. The close similarity of the cyclase responsiveness to hormones of the mouse and rat TALs makes it possible to interpret the micropuncture data obtained in vivo in the rat superficial (S) and juxtamedullary (JM) nephrons, in the light of the in vitro data obtained in the mouse. Long-term treatment of Brattleboro rats with ADH also elicits differential effects along the TAL. Their consequences on the function of the S and JM nephrons are also examined. There are several indications supporting the view that the newly described hormonal effects in the mouse and rat are of physiological relevance.

Effect of metabolic inhibitors on urine osmolality and electrolyte excretion

1963 ◽  
Vol 204 (6) ◽  
pp. 1065-1070 ◽  
Author(s):  
Wolfgang Herms ◽  
Richard L. Malvin
Keyword(s):  
Renal Artery ◽  
Distal Tubule ◽  
Urine Osmolality ◽  
Metabolic Inhibitors ◽  
Before And After ◽  
K Secretion ◽  
Flow Experiments ◽  
K Transport ◽  
Stop Flow

The in vivo effects of aerobic and anaerobic metabolic inhibitors on renal Na and K transport and concentrating ability were studied in dogs. Two aerobic inhibitors (sodium cyanide and hydroxylamine) and two anaerobic inhibitors (iodoacetate and triethyleneiminotriazine) were infused into one renal artery. Urine was collected separately from both kidneys and urine osmolality, Na, and K concentrations were measured. In addition, stop-flow experiments were done before and after infusion of NaCN and iodoacetate into one renal artery. Aerobic inhibitors resulted in a decrease in urine osmolality associated with a large increase in Na excretion. Anaerobic inhibitors resulted in a similar decrease in urine osmolality with only a minimal increase in Na excretion. In stop-flow experiments cyanide blocked Na and K transport in the distal tubule. Iodoacetate had no demonstrable effect on distal Na or K transport, but did abolish K secretion which was presumed to take place in the collecting ducts. These results suggest that Na and K transport in medullary regions is largely dependent on energy derived from anaerobic glycolysis.

Site of formation of kinins in the dog nephron

1978 ◽  
Vol 234 (1) ◽  
pp. F36-F40 ◽  
Author(s):  
A. G. Scicli ◽  
R. Gandolfi ◽  
O. A. Carretero
Keyword(s):  
Distal Part ◽  
Sodium Concentration ◽  
Renal Papilla ◽  
Distal Nephron ◽  
Water Reabsorption ◽  
Sodium Potassium ◽  
Kallikrein Activity ◽  
Flow Experiments ◽  
Stop Flow ◽  
Second Peak

The site of formation of kinins in the nephron was determined by stop-flow studies in dogs. Klinin, inulin, sodium, potassium concentrations were measured in the fractions collected during the stop-flow procedures. In addition, in three of the 17 stop-flow experiments, kallikrein activity was also measured. The highest kinin concentration after correction for water reabsorption was found in the fractions that were probably trapped in the distal part of the nephron. Either one or two peak was located either in the fraction overlapping (in one instance) or in the fractions coming prior to the fractions with the highest concentration of potassium. This first peak was present in all but one of the stop-flow experiments and was greater than the second peak. The second peak of kinins was found in 13 of the 17 stop-flow exeriments and was located in the fractions with the lowest sodium concentration. Those fractions with the lowest sodium concentration. Those fractions with the lowest sodium concentration also had the highest kallikrein concentration. No evidence of kinin formation was found in the fractions representing the proximal nephron. We conclude, therefore, that kinins are formed in the distal part of the nephron, with the highest concentration found in the last part of the distal nephron and/or in the renal papilla and pelvis.

Distal site of action of parathyroid hormone on phosphate reabsorption

1975 ◽  
Vol 229 (6) ◽  
pp. 1556-1560 ◽  
Author(s):  
FG Knox ◽  
C Lechene
Keyword(s):  
Parathyroid Hormone ◽  
Proximal Tubule ◽  
Phosphate Transport ◽  
Distal Nephron ◽  
Phosphate Reabsorption ◽  
Site Of Action ◽  
Flow Experiments ◽  
Filtered Load ◽  
Stop Flow ◽  
Distal Site

The sites of inhibited phosphate transport following administration of bovine parathyroid hormone (bPTH) to thyroparathyroidectomized (TPTX) dogs were investigated. Phosphate reabsorption by the proximal and distal nephron was studied using recollection micropuncture, stop-flow methodology, and electron-probe microanalysis. Following bPTH, delivery of phosphate from the proximal tubule increased from 26 to 37% of the filtered load, P less than .01. Fractional phosphate excretion increased from 2.3 +/- 1.5 to 21.4 +/- 2.3%, P less than .001. The increased delivery of phosphate at the point of micropuncture in the proximal tubule accounted for approximately half of the phosphaturia. In six TPTX dogs, which were saline loaded, similiar increases in phosphate delivery from the proximal tubule from 27 +/- 1 to 36 +/- 2% of the filtered load resulted in a strikingly smaller phosphaturia, 5.1 +/- 1 to 9.8 +/- 2.4%, NS. In stop-flow experiments, phosphate concentratin ratios were slightly increased in the proximal nephron and markedly increased in the distal nephron following bPTH. It is concluded that parathyroid hormone markedly decreases phosphate transport in the distal nephron.

scholarly journals Connecting tubule glomerular feedback antagonizes tubuloglomerular feedback in vivo

2010 ◽  
Vol 299 (6) ◽  
pp. F1374-F1378 ◽  
Author(s):  
H. Wang ◽  
J. L. Garvin ◽  
M. A. D'Ambrosio ◽  
Y. Ren ◽  
O. A. Carretero
Keyword(s):  
Tubuloglomerular Feedback ◽  
Afferent Arteriole ◽  
In Vitro Experiments ◽  
Nacl Transport ◽  
Connecting Tubule ◽  
Vasoconstrictor Effect ◽  
Flow Pressure ◽  
Stop Flow

In vitro experiments showed that the connecting tubule (CNT) sends a signal that dilates the afferent arteriole (Af-Art) when Na+ reabsorption in the CNT lumen increases. We call this process CNT glomerular feedback (CTGF) to differentiate it from tubuloglomerular feedback (TGF), which is a cross talk between the macula densa (MD) and the Af-Art. In TGF, the MD signals the Af-Art to constrict when NaCl transport by the MD is enhanced by increased luminal NaCl. CTGF is mediated by CNT Na+ transport via epithelial Na+ channels (ENaC). However, we do not know whether CTGF occurs in vivo or whether it opposes the increase in Af-Art resistance caused by TGF. We hypothesized that CTGF occurs in vivo and opposes TGF. To test our hypothesis, we conducted in vivo micropuncture of individual rat nephrons, measuring stop-flow pressure (PSF) as an index of glomerular filtration pressure. To test whether activation of CTGF opposes TGF, we used benzamil to block CNT Na+ transport and thus CTGF. CTGF inhibition with the ENaC blocker benzamil (1 μM) potentiated the decrease in PSF at 40 and 80 nl/min. Next, we tested whether we could augment CTGF by inhibiting NaCl reabsorption in the distal convoluted tubule with hydrochlorothiazide (HCTZ, 1 mM) to enhance NaCl delivery to the CNT. In the presence of HCTZ, benzamil potentiated the decrease in PSF at 20, 40, and 80 nl/min. We concluded that in vivo CTGF occurs and opposes the vasoconstrictor effect of TGF.

Insulin stimulates NaCl transport in isolated perfused MTAL of Henle's loop of rabbit kidney

1994 ◽  
Vol 267 (2) ◽  
pp. F265-F270 ◽  
Author(s):  
O. Ito ◽  
Y. Kondo ◽  
N. Takahashi ◽  
K. Kudo ◽  
Y. Igarashi ◽  
...  
Keyword(s):  
Kinase Inhibitor ◽  
Basolateral Membrane ◽  
Rabbit Kidney ◽  
Thick Ascending Limb ◽  
Maximal Effect ◽  
Nacl Transport ◽  
Luminal Membrane ◽  
Camp Analogue

To elucidate the mechanism of Na+ retention by insulin in vivo, the direct tubular effect of insulin on NaCl transport in the in vitro microperfused medullary thick ascending limb of Henle (MTAL) was examined. Insulin at 10(-6) mol/l in the bath increased transepithelial voltage (Vte) from 3.1 +/- 0.3 to 5.7 +/- 0.3 mV (n = 12, P < 0.0001). The effect of insulin on Vte was dependent on its concentration, and the half-maximal effect of insulin was observed at 5 x 10(-9) mol/l. Insulin at 10(-6) mol/l also caused a significant decrease of luminal Cl- concentration from 85.4 +/- 5.0 to 62.8 +/- 3.0 mmol/l (n = 5, P < 0.002) when the lumen was microperfused constantly at less than 1 nl/min. Insulin at 10(-6) mol/l also increased net lumen-to-bath Cl- flux (JCl) from 143 +/- 15 to 292 +/- 37 pmol.mm-1.min-1 (n = 5, P < 0.004). When the Na(+)-K(+)-adenosinetriphosphatase (Na(+)-K(+)-ATPase) in the basolateral membrane was blocked by 10(-4) mol/l ouabain, the insulin-mediated increase in Vte was completely suppressed. When the Na(+)-K(+)-2Cl- cotransporter in the luminal membrane of the MTAL was blocked by 10(-4) mol/l furosemide, the insulin-mediated increase in Vte was also abolished. To test whether adenosine 3',5'-cyclic monophosphate (cAMP) contributes to the action of insulin, we examined the effect of cAMP analogue and cAMP-dependent protein kinase inhibitor on the action of insulin. A maximal concentration (5 x 10(-4) mol/l) of dibutyryl-cAMP (DBcAMP) increased Vte and JCl.(ABSTRACT TRUNCATED AT 250 WORDS)

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