scholarly journals Maturation of rabbit proximal straight tubule chloride/base exchange

1998 ◽  
Vol 274 (5) ◽  
pp. F883-F888 ◽  
Author(s):  
Mehul Shah ◽  
Raymond Quigley ◽  
Michel Baum
Keyword(s):  
Adult Rabbit ◽  
Albumin Solution ◽  
Nacl Transport ◽  
Base Exchange ◽  
Straight Tubule ◽  
Volume Absorption ◽  
Straight Tubules ◽  
Proximal Straight Tubule ◽  
Proximal Tubular

The present in vitro microperfusion study compared the mechanism and rates of NaCl transport in neonatal and adult rabbit proximal straight tubules. In proximal straight tubules perfused with a late proximal tubular fluid and bathed in a serumlike albumin solution, the rate of volume absorption ( J V) was 0.54 ± 0.10 and 0.12 ± 0.05 nl ⋅ mm−1 ⋅ min−1in adults and neonates, respectively ( P < 0.05). With the addition of 10−5 M bath ouabain, J Vdecreased to 0.27 ± 0.07 and −0.03 ± 0.04 nl ⋅ mm−1 ⋅ min−1in adult and neonatal tubules, respectively ( P < 0.05), consistent with lower rates of active and passive NaCl transport in the neonatal proximal straight tubule. The effect of luminal sodium and chloride removal on intracellular pH was used to assess the relative rates of Na+/H+and Cl−/base exchange. The rates of Na+/H+and Cl−/base exchange were approximately fivefold less in neonatal proximal straight tubules than adult tubules. In both neonatal and adult proximal straight tubules, the rate of Cl−/base exchange was not affected by formate, bicarbonate, or cyanide and acetazolamide, consistent with Cl−/OH−exchange. These data demonstrate an increase in proximal straight tubule NaCl transport during postnatal renal development.

Evidence that parallel Na+-H+ and Cl(-)-HCO3-(OH-) antiporters transport NaCl in the proximal tubule

1987 ◽  
Vol 252 (2) ◽  
pp. F338-F345 ◽  
Author(s):  
M. Baum
Keyword(s):  
Carbonic Anhydrase ◽  
Proximal Tubule ◽  
Driving Forces ◽  
Disulfonic Acid ◽  
Albumin Solution ◽  
Nacl Transport ◽  
Volume Absorption ◽  
Proximal Tubular ◽  
High Chloride

The present in vitro microperfusion study examined whether active NaCl transport in the proximal convoluted tubule (PCT) occurs via parallel Na+-H+ and Cl(-)-HCO3-(OH-) exchangers. PCT were perfused with a high-chloride, low-bicarbonate solution simulating late proximal tubular fluid, and were bathed in a similar solution containing 6 g/dl albumin. In this setting the driving forces responsible for passive NaCl transport are eliminated. Addition of 0.1 or 0.5 mM luminal 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS), 0.5 mM luminal 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), or 0.1 mM bath ethoxyzolamide, a lipophilic carbonic anhydrase inhibitor, resulted in an approximately 50% reduction in volume absorption. Inhibition of the Na+-H+ antiporter with 1.0 mM luminal amiloride inhibited volume absorption by 50%. The transepithelial potential difference (PD) was not significantly different from zero, consistent with an electroneutral mechanism for active NaCl transport. The effect of a Cl(-)-HCO3-(OH-) exchanger on acidification was examined in PCT perfused with an ultrafiltrate-like solution and bathed in a serumlike albumin solution. Addition of 0.5 mM DIDS did not significantly decrease volume absorption, demonstrating that luminal DIDS did not result in a nonspecific decrease in solute transport. Luminal DIDS significantly stimulated bicarbonate absorption, consistent with a Na+-H+ antiporter running in parallel with a Cl(-)-HCO3-(OH-) antiporter, which exchanges luminal Cl- for cellular HCO3- (or OH-). In conclusion, these data are consistent with parallel Na+-H+ and Cl(-)-HCO3-(OH-) antiporters mediating neutral active NaCl transport in the PCT.

Heterogeneity of chloride/base exchange in rabbit superficial and juxtamedullary proximal convoluted tubules

1995 ◽  
Vol 268 (5) ◽  
pp. F847-F853 ◽  
Author(s):  
J. N. Sheu ◽  
R. Quigley ◽  
M. Baum
Keyword(s):  
Intracellular Ph ◽  
Rate Of Change ◽  
Disulfonic Acid ◽  
Nacl Transport ◽  
Base Exchange ◽  
Volume Absorption ◽  
Proximal Tubular ◽  
Presence And Absence ◽  
Convoluted Tubules

Active transcellular NaCl transport in the proximal convoluted tubule (PCT) is via apical parallel Na/H and Cl/base exchange. The mechanism of Cl/base exchange remains unclear. The present in vitro microperfusion study examined the mechanism of Cl/base exchange in superficial and juxtamedullary PCT by examining the rate of change in intracellular pH in response to luminal Cl removal. In superficial PCT the rate of Cl/base exchange was 24.0 +/- 2.3 without formate, 36.4 +/- 6.6 with 10 microM formate (P < 0.05), and 43.6 +/- 2.8 pmol.mm-1.min-1 (P < 0.001) with 1 mM luminal formate. Cl/base exchange was inhibited by luminal 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) in the presence and absence of formate. In juxtamedullary PCT, Cl/base exchange was 22.2 +/- 3.8 without formate and 25.0 +/- 5.4 pmol.mm-1.min-1 in the presence of 1 mM luminal formate [P = not significant (NS)]. Cl/base exchange was inhibited by luminal DIDS in juxtamedullary PCT. The rates of Cl/base exchange in both superficial and juxtamedullary PCT were not affected by 0.1 mM acetazolamide and 2 mM cyanide and were the same in the presence and absence of HCO3/CO2, consistent with Cl/OH rather than Cl/HCO3 exchange. To examine the effect of formate on PCT transport, tubules were perfused with a high-Cl solution without organics simulating late proximal tubular fluid. In superficial PCT net volume absorption (JV) was 0.00 +/- 0.05 in the absence of formate and 0.14 +/- 0.06 nl.mm-1.min-1 in the presence of 1 mM formate (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary acidification: CO2 transport by the rabbit proximal straight tubule

1977 ◽  
Vol 232 (1) ◽  
pp. F20-F25 ◽  
Author(s):  
D. G. Warnock ◽  
M. B. Burg
Keyword(s):  
Blood Flow ◽  
Renal Blood Flow ◽  
Functional Heterogeneity ◽  
High Permeability ◽  
Straight Tubule ◽  
Urinary Acidification ◽  
Straight Tubules ◽  
Proximal Straight Tubule ◽  
Tubule Fluid

Proximal straight tubules from rabbit kidneys were perfused in vitro in order to study transport of bicarbonate. Total CO2 content was measured in perfused and collected tubule fluid, using microcalorimetry. When the initial perfusate and bath contained 25 mM bicarbonate, the concentration of total CO2 decreased in the collected tubule fluid, indicating net reabsorption of bicarbonate. When the initial perfusate contained no bicarbonate and the bath contained 25 mM bicarbonate, total CO2 appeared in the collected tubule fluid. The rate at which total CO2 appeared in the tubule fluid was rapid, indicating a high permeability. Proximal straight tubules from superficial and juxtamedullary nephrons were compared and found to differ in permeability to CO2 and in transport rate. This functional heterogeneity may affect urinary acidification when there is redistribution of renal blood flow.

scholarly journals Maturation of proximal straight tubule NaCl transport: role of thyroid hormone

2000 ◽  
Vol 278 (4) ◽  
pp. F596-F602 ◽  
Author(s):  
Mehul Shah ◽  
Raymond Quigley ◽  
Michel Baum
Keyword(s):  
Thyroid Hormone ◽  
Apical Membrane ◽  
Organic Solutes ◽  
Nacl Transport ◽  
Straight Tubule ◽  
Proximal Straight Tubule ◽  
Tubule Fluid ◽  
High Chloride

We have recently demonstrated that the rates of both active and passive proximal straight tubule (PST) NaCl transport in neonatal rabbits were less than in adults. In this segment NaCl entry across the apical membrane is via parallel Na+/H+ and Cl−/OH− exchangers, which increases in activity with maturation. The present in vitro microperfusion study examined whether thyroid hormone plays a role in the maturational increase in PST NaCl transport. Neonatal and adult PST were perfused with a high-chloride-low bicarbonate solution without organic solutes, simulating late proximal tubule fluid. Thyroid hormone-treated neonates had a higher rate of PST total and passive NaCl transport. In 8-wk-old animals that were hypothyroid since birth, the maturational increase in total and passive NaCl transport was prevented. Thyroid treatment for 4 days in hypothyroid 8-wk-old rabbits increased the rate of both total and passive NaCl transport. The maturational increases in both Na+/H+ and Cl−/OH− exchange activities were blunted in 8-wk-old hypothyroid animals and increased to control levels with thyroid treatment. This study demonstrates that thyroid hormone is a factor responsible for the maturational increase in both active and passive PST NaCl transport.

scholarly journals Neonatal rabbit proximal tubule basolateral membrane Na+/H+antiporter and Cl−/base exchange

1999 ◽  
Vol 276 (6) ◽  
pp. R1792-R1797 ◽  
Author(s):  
Mehul Shah ◽  
Raymond Quigley ◽  
Michel Baum
Keyword(s):  
Proximal Tubule ◽  
Intracellular Ph ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Fluorescent Dye ◽  
Adult Rabbit ◽  
Base Exchange ◽  
Straight Tubules ◽  
Exchange Activity

The present in vitro microperfusion study examined the maturation of Na+/H+antiporter and Cl−/base exchanger on the basolateral membrane of rabbit superficial proximal straight tubules (PST). Intracellular pH (pHi) was measured with the pH-sensitive fluorescent dye 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein in neonatal and adult superficial PST. Na+/H+antiporter activity was examined after basolateral Na+ addition in tubules initially perfused and bathed without Na+. Neonatal Na+/H+antiporter activity was ∼40% that of adult segment (9.7 ± 1.5 vs. 23.7 ± 3.2 pmol ⋅ mm−1 ⋅ min−1; P < 0.001). The effect of bath Cl− removal on pHi was used to assess the rates of basolateral Cl−/base exchange. In both neonatal and adult PST, the Cl−/base exchange activity was significantly higher in the presence of 25 mM[Formula: see text] than in the absence of[Formula: see text] and was inhibited by cyanide and acetazolamide, consistent with Cl−/[Formula: see text]exchange. The proton flux rates in the presence of bicarbonate in neonatal and adult tubules were 14.1 ± 3.6 and 19.5 ± 3.5 pmol ⋅ mm−1min−1, respectively ( P = NS), consistent with a mature rate of Cl−/[Formula: see text]exchanger activity in neonatal tubules. Basolateral Cl−/base exchange activity in the absence of CO2 and[Formula: see text], with luminal and bath cyanide and acetazolamide, was greater in adult than in neonatal PST and inhibited by bath DIDS consistent with a maturational increase in Cl−/OH−exchange. We have previously shown that the rates of the apical membrane Na+/H+antiporter and Cl−/base exchanger were approximately fivefold lower in neonatal compared with adult rabbit superficial PST. These data demonstrate that neonatal PST basolateral membrane Na+/H+antiporter and Cl−/base exchanger activities are relatively more mature than the Na+/H+antiporter and Cl−/base exchangers on the apical membrane.

scholarly journals QUANTITATIVE HISTOCHEMISTRY OF URIDINE DIPHOSPHOGLUCOSE-PYROPHOSPHATASE AND URIDINE DIPHOSPHOGLUCOSE-PYROPHOSPHORYLASE IN DEVELOPING RAT KIDNEY

1974 ◽  
Vol 22 (11) ◽  
pp. 1034-1038 ◽  
Author(s):  
CLINTON N. CORDER ◽  
MARK L. BERGER ◽  
OLIVER H. LOWRY
Keyword(s):  
Rat Kidney ◽  
Development Activity ◽  
Quantitative Histochemistry ◽  
Small Arteries ◽  
Straight Tubule ◽  
Adult Kidney ◽  
Straight Tubules ◽  
Proximal Straight Tubule ◽  
Developing Rat ◽  
Made In

Quantitative histochemical measurements of two enzymes of uridine diphosphoglucose (UDPG) metabolism have been made in the developing rat kidney nephron. Kidneys were examined from -4 days to 44 days of age. In the adult kidney, UDPG-pyrophosphatase was concentrated in proximal convoluted and straight tubules. During maturation, activity decreased in glomeruli, increased in the proximal tubule and changed little elsewhere in the nephron. UDPG-pyrophosphorylase revealed a different pattern. Activity was more nearly uniformly distributed throughout the nephron but was highest in the proximal straight tubule and ascending limb of Henle. During development, activity was unchanged or increased in glomeruli and small arteries and increased elsewhere, particularly in the proximal straight tubule and ascending limb of Henle.

Mechanism of bicarbonate exit across basolateral membrane of rabbit proximal straight tubule

1987 ◽  
Vol 252 (1) ◽  
pp. F11-F18 ◽  
Author(s):  
S. Sasaki ◽  
T. Shiigai ◽  
N. Yoshiyama ◽  
J. Takeuchi
Keyword(s):  
Negative Charge ◽  
Driving Forces ◽  
Basolateral Membrane ◽  
Disulfonic Acid ◽  
Exit Mechanism ◽  
Total Replacement ◽  
Straight Tubules ◽  
Proximal Straight Tubule ◽  
Basolateral Membrane Potential

To clarify the mechanism(s) of HCO3- (or related base) transport across the basolateral membrane, rabbit proximal straight tubules were perfused in vitro, and intracellular pH (pHi) and Na+ activity (aiNa) were measured by double-barreled ion-selective microelectrodes. Lowering bath HCO3- from 25 to 5 mM at constant PCO2 depolarized basolateral membrane potential (Vbl), and reduced pHi. Most of these changes were inhibited by adding 1 mM 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS) to the bath. Total replacement of bath Na+ with choline also depolarized Vbl and reduced pHi, and these changes were also inhibited by SITS. Reduction in aiNa was observed when bath HCO3- was lowered. Taken together, these findings suggest that HCO3- exists the basolateral membrane with Na+ and negative charge. Calculation of the electrochemical driving forces suggests that the stoichiometry of HCO3-/Na+ must be larger than two for maintaining HCO3- efflux. Total replacement of bath Cl- with isethionate depolarized Vbl gradually and increased pHi slightly, implying the existence of a Cl(-)-related HCO3- exit mechanism. The rate of decrease in pHi induced by lowering bath HCO3- was slightly reduced (20%) by the absence of bath Cl-. Therefore, the importance of Cl(-)-related HCO3- transport is small relative to total basolateral HCO3- exit. Accordingly, these data suggest that most of HCO3- exits the basolateral membrane through the rheogenic Na+/HCO3- cotransport mechanism with a stoichiometry of HCO3-/Na+ of more than two.

Transport of potassium in the rabbit pars recta

1982 ◽  
Vol 242 (3) ◽  
pp. F226-F237 ◽  
Author(s):  
J. Work ◽  
S. L. Troutman ◽  
J. A. Schafer
Keyword(s):  
Bathing Solution ◽  
Passive Permeability ◽  
Straight Tubule ◽  
Straight Tubules ◽  
Proximal Straight Tubule ◽  
Pars Recta ◽  
K Secretion ◽  
Unidirectional Fluxes ◽  
K Concentration ◽  
K Permeability

Unidirectional fluxes of 42K+ and 86Rb+ were measured in isolated perfused segments of proximal straight tubules and no differences were found between the two isotopes for the same flux determination. In the three segments examined (the early and late superficial proximal straight tubule and the juxtamedullary proximal straight tubule) there was apparent net active K+ secretion as demonstrated by differences in the unidirectional fluxes of 2.6, 3.2, and 4.8 pmol.min-1.mm-1, respectively. However, in contrast to the expectations for active K+ secretion, the bath-to-lumen fluxes were unaffected by 0.1 mM ouabain added to the bathing solution, and in the early superficial and juxtamedullary segments these fluxes were directly proportional to the K+ concentration of the bathing solution over a range of concentrations. Apparent K+ permeability coefficients were calculated from lumen-to-bath fluxes to be 0.14 +/- 0.02, 0.10 +/- 0.02, and 0.52 +/- 0.07 micrometers.s-1 in the early and late superficial and juxtamedullary segments, respectively. Based on these data and on a mathematical analysis, we have concluded that active K+ secretion of the magnitude measured would have little importance in determining the K+ load delivered to the descending limb of the loop of Henle. However, the higher passive permeability of the juxtamedullary segment would allow significant net K+ secretion if the outer medullary interstitium had even a moderately elevated K+ concentration.

Inhibition of Jv by ANF in rat proximal straight tubules requires angiotensin

1989 ◽  
Vol 257 (5) ◽  
pp. F907-F911 ◽  
Author(s):  
J. L. Garvin
Keyword(s):  
Angiotensin Ii ◽  
Atrial Natriuretic Factor ◽  
Second Messenger ◽  
Fluid Absorption ◽  
Straight Tubule ◽  
Cyclic Monophosphate ◽  
Natriuretic Factor ◽  
Straight Tubules ◽  
Proximal Straight Tubule ◽  
Messenger System

The effects of atrial natriuretic factor (ANF) on fluid absorption (Jv) by isolated perfused proximal straight tubules of rats were investigated. ANF alone (10(-8) M) added to the bath had no significant effect on absorption. In contrast, when tubules were first treated with 1.6 X 10(-10) M angiotensin II, this same concentration of ANF lowered fluid absorption from 0.99 +/- 0.03 to 0.69 +/- 0.02 nl.mm-1.min-1. A lower dose of ANF, 2 X 10(-10) M, reduced fluid absorption in the presence of angiotensin II from 1.13 +/- 0.06 to 0.65 +/- 0.05 nl.mm-1.min-1, an inhibition of 40%. Since guanosine 3',5'-cyclic monophosphate (cGMP) is reportedly part of the second messenger system of ANF, the effects of dibutyryl-cGMP (DBcGMP) on fluid absorption were studied. This membrane-permeant form of cGMP mimicked the effects of ANF, reducing fluid absorption from 1.15 +/- 0.18 to 0.54 +/- 0.08 nl.mm-1.min-1. These studies suggested the following: 1) ANF can regulate fluid absorption in the proximal nephron; 2) this inhibition occurs only in the presence of angiotensin; and 3) cGMP is part of the second messenger system of ANF in the rat proximal straight tubule, as it is in other tissues.

Bicarbonate and ammonia transport in isolated perfused rat proximal straight tubules

1987 ◽  
Vol 253 (2) ◽  
pp. F277-F281 ◽  
Author(s):  
J. L. Garvin ◽  
M. A. Knepper
Keyword(s):  
Fluid Transport ◽  
Distal Tubule ◽  
Co2 Absorption ◽  
Straight Tubule ◽  
Straight Tubules ◽  
Proximal Straight Tubule ◽  
Total Ammonia ◽  
The Mean ◽  
Disequilibrium Ph

Bicarbonate, ammonia, and fluid transport were studied in isolated perfused proximal straight tubules from rats. The mean rate of fluid absorption (0.77 nl X min-1 X mm-1) and the mean rate of total CO2 absorption (42 pmol X min-1 X mm-1) exceeded corresponding rates measured previously in rabbit proximal straight tubules. The limiting total CO2 concentration when the tubules were perfused at slow flow rates was 5 mM, a value similar to those reported previously for rat proximal convoluted tubules and thick ascending limbs. When rat proximal straight tubules were perfused and bathed with solutions containing 1 mM total ammonia at slow perfusion rates, the measured total ammonia concentration in collected fluid rose to a level predicted by the diffusion trapping model of ammonia secretion in the absence of a luminal disequilibrium pH. We conclude the proximal straight tubule of the rat can absorb bicarbonate at a rate that can account for a large portion of the bicarbonate absorption measured in vivo between the late proximal convoluted tubule and the early distal tubule, the rat proximal straight tubule is capable of transepithelial ammonia secretion, most likely by NH3 diffusion down a concentration gradient generated by luminal acidification, and the rat proximal straight tubule apparently does not generate a luminal disequilibrium pH despite the occurrence of proton secretion, implying the presence of endogenous luminal carbonic anhydrase.

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