Effects of 20-HETE and 19(S)-HETE on rabbit  proximal straight tubule volume transport

The kidney has the highest abundance of cytochrome P-450 of all extrahepatic organs. Within the kidney, the highest concentration of cytochrome P-450 is found in the proximal tubule. Whether 20- or 19( S)-hydroxyeicosatetraenoic acid (HETE), the major P-450 metabolites of arachidonic acid in the proximal tubule, affect transport in this segment has not been previously investigated. We examined the direct effects of 20- and 19( S)-HETE on volume absorption ( J v) in the rabbit proximal straight tubule (PST). Production of 20-HETE by rabbit PST was demonstrated by incubating microdissected tubules with [3H]arachidonic acid and separating the lipid extract by HPLC. There was significant conversion of [3H]arachidonic acid to 20-HETE in control tubules that was inhibited by 10− 5 M N-methylsulfonyl-12,12-dibromododec-11-enamide (DDMS). Addition of exogenous 20-HETE had no effect on PST volume transport. However, inhibition of endogenous production of 20-HETE using DDMS stimulated transport. In the presence of DDMS, 20-HETE inhibited PST J v. 19( S)-HETE in the bathing solution stimulated PST J v alone and in the presence of DDMS. Thus ω- and ω-1-hydroxylase products of arachidonic acid have direct effects on PST transport. Endogenous production of 20-HETE may play a role in tonic suppression of transport and may therefore be an endogenous regulator of transport in the proximal tubule.

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Vitamin D3 metabolites increase [Ca2+]i in rabbit renal proximal straight tubule cells

AJP Renal Physiology ◽

10.1152/ajprenal.1991.260.5.f757 ◽

1991 ◽

Vol 260 (5) ◽

pp. F757-F763 ◽

Cited By ~ 1

Author(s):

M. Suzuki ◽

S. Kurihara ◽

Y. Kawaguchi ◽

O. Sakai

Keyword(s):

Vitamin D ◽

Proximal Tubule ◽

Ion Concentration ◽

Rabbit Kidney ◽

Vitamin D Metabolites ◽

Dihydroxyvitamin D3 ◽

Straight Tubule ◽

Proximal Straight Tubule ◽

Tubule Cells ◽

Free Media

Vitamin D metabolites exert both acute and chronic influences on proximal tubule function. To further evaluate vitamin D action on the kidney, we examined the immediate effects of vitamin D metabolites on cytoplasmic calcium ion concentration [( Ca2+]i), using fura-2 and patch-clamp method in cultured proximal straight tubule cells of rabbit kidney. 1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] and 25-hydroxyvitamin D3 [25(OH)D3] evoked a transient rise in [Ca2+]i, and 24,25-dihydroxyvitamin D3 [24,25(OH)2D3] caused a sustained rise in [Ca2+]i; all effects were dose dependent. [Ca2+]i transient, evoked by 1,25(OH)2D3 alone, was abolished in Ca(2+)-free media. Pretreatment of cells in Ca(2+)-free media with caffeine (4 mM) or ryanodine (1 microM) to deplete Ca2+ store of endoplasmic reticulum or with TMB-8 (5 mM) to block Ca2+ release from storage blunted the effect of 25(OH)D3 on [Ca2+]i but not of 24,25(OH)2D3. Data were also supported by activities of Ca-dependent K channel and show that these three vitamin D metabolites in pharmacological doses increase [Ca2+]i of proximal tubule cells from different sources.

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Transport of potassium in the rabbit pars recta

AJP Renal Physiology ◽

10.1152/ajprenal.1982.242.3.f226 ◽

1982 ◽

Vol 242 (3) ◽

pp. F226-F237 ◽

Cited By ~ 3

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.

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Maturation of rabbit proximal straight tubule chloride/base exchange

AJP Renal Physiology ◽

10.1152/ajprenal.1998.274.5.f883 ◽

1998 ◽

Vol 274 (5) ◽

pp. F883-F888 ◽

Cited By ~ 5

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.

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Effect of methionine sulfoximine on glutathione and amino acid levels in the nephron

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1976.231.5.1536 ◽

1976 ◽

Vol 231 (5) ◽

pp. 1536-1540 ◽

Cited By ~ 28

Author(s):

JE Brehe ◽

AW Chan ◽

TR Alvey ◽

HB Burch

Keyword(s):

Amino Acid ◽

Proximal Tubule ◽

Methionine Sulfoximine ◽

Outer Cortex ◽

Straight Tubule ◽

Freeze Dried ◽

Proximal Straight Tubule ◽

Amino Acid Levels ◽

Convoluted Tubules ◽

Proximal Tubule Segments

The effect of L-methionine-DL-sulfoximine (MSO) on renal glutathione concentration and aspartic acid transport has been studied by analyses of parts of individual freeze-dried glomeruli, early and late proximal convoluted, early and late proximal straight, and distal straight and convoluted tubules, and patches from thinlimb and papilla areas. Glutathione normally varies threefold along the kidney nephron, being highest in the convoluted and early straight proximal tubule, lowest in the distal straight tubule. Large loads of aspartate cause 20% diminution of glutathione in outer cortex, due entirely to changes in proximal tubule segments. MSO alone lowers glutathione 90% in all parts of the proximal tubule, with no change elsewhere. MSO does not affect the large increase in aspartate in proximal tubules caused by saturating aspartate loads, suggesting that glutathione is not directly involved in transport of this amino acid. Aspartate loads cause a large increase in renal glutamine, which is especially marked in the proximal straight tubule. MSO effectively blocks this increase and depresses tissue glutamine below normal levels.

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Potassium channels in the luminal membrane of rabbit proximal straight tubule. Evidence from vesicle studies

Biochemical Journal ◽

10.1042/bj2620271 ◽

1989 ◽

Vol 262 (1) ◽

pp. 271-275 ◽

Cited By ~ 3

Author(s):

C Jacobsen ◽

H Røigaard-Petersen ◽

M I Sheikh

Keyword(s):

Potassium Channels ◽

Proximal Tubule ◽

Membrane Vesicles ◽

Diffusion Potential ◽

K Channels ◽

Straight Tubule ◽

Cation Selectivity ◽

Luminal Membrane ◽

Proximal Straight Tubule ◽

Pars Recta

The characteristics of 86Rb+ fluxes through K+ channels in luminal-membrane vesicles isolated from the pars recta of rabbit proximal tubule were studied. In KCl-loaded vesicles from the pars recta, transient accumulation of 86Rb+ is observed which is modestly inhibited by BaCl2 and blocked by CdCl2. The isotope accumulation is driven by an electrical diffusion potential, as shown in experiments using either these membrane vesicles loaded with different anions, or an outwardly directed Li+ gradient with a Li+ ionophore. The vesicles containing the channel show a cation selectivity with the order K+ greater than Rb+ greater than choline+ greater than or equal to Li+ greater than Na+. The CdCl2-sensitive 86Rb+ flux is dependent on intravesicular Ca2+. Increasing concentrations of Ca2+ gradually decreased the 86Rb+ uptake and at 1 microM-Ca2+ the CdCl2-sensitive isotope flux is nearly abolished.

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Lack of a direct effect of atrial natriuretic factor in the rabbit proximal tubule

AJP Renal Physiology ◽

10.1152/ajprenal.1986.250.1.f66 ◽

1986 ◽

Vol 250 (1) ◽

pp. F66-F69 ◽

Cited By ~ 4

Author(s):

M. Baum ◽

R. D. Toto

Keyword(s):

Proximal Tubule ◽

Atrial Natriuretic Factor ◽

Bathing Solution ◽

Volume Absorption ◽

Natriuretic Factor ◽

Clearance Studies ◽

Convoluted Tubules ◽

Atrial Natriuretic

Whole animal clearance studies and in vitro microperfusion studies were performed to examine the effect of atrial natriuretic factor (ANF) on the rabbit proximal tubule. Infusion of ANF into rabbits resulted in an increase in glomerular filtration rate and a natriuresis and diuresis. To determine whether ANF has a direct proximal tubule effect to account for part of the observed natriuresis, proximal convoluted tubules (PCT) and proximal straight tubules (PST) were perfused in vitro. Addition of 10(-9) M ANF, a concentration recently measured in vivo during volume expansion, to the bathing solution of PCT caused no significant change in volume absorption. Addition of a pharmacological concentration of ANF (10(-7) M) to either the bathing solution or the luminal perfusate of PCT resulted in no change in volume absorption. When added to the bathing solution of PST, 10(-7) M ANF did not have an effect on volume absorption. ANF did not affect the transepithelial potential difference in any protocol. In conclusion, these data show that ANF does not affect transport directly in the proximal tubule.

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Localization of arginine synthesis along rat nephron

AJP Renal Physiology ◽

10.1152/ajprenal.1990.259.6.f916 ◽

1990 ◽

Vol 259 (6) ◽

pp. F916-F923 ◽

Cited By ~ 11

Author(s):

O. Levillain ◽

A. Hus-Citharel ◽

F. Morel ◽

L. Bankir

Keyword(s):

Proximal Tubule ◽

Urine Concentration ◽

Precursor Concentration ◽

Whole Body ◽

Straight Tubule ◽

Nephron Segments ◽

Proximal Straight Tubule ◽

Isolated Rat

Arginine production was measured in isolated rat nephron segments. Segments were incubated with 0.3 mM aspartate and 0.1 mM L-[ureido-14C]-citrulline in a sealed chamber. Arginase and urease were added to the medium to hydrolyze arginine and to release 14CO2, which was trapped in KOH and counted. Arginine synthesis was found only in the proximal tubule, with decreasing intensity from proximal convoluted (PCT) to proximal straight tubule (PST). Results were as follows (in fmol.min-1.mm tubule length-1): PCT, 122 +/- 15; cortical PST, 71 +/- 6; outer medullary PST, 41 +/- 4; all other segments, less than 6. Arginine synthesis changed almost proportionally with precursor concentration of less than or equal to 0.4 mM. We had shown previously that PST but not PCT was able to hydrolyze arginine into urea and ornithine. In this study arginine was further hydrolyzed in cortical (40%) and medullary (64%) PST but not in PCT. These observations suggest that the arginine formed in PCT contributes to the maintenance of the whole body arginine pool, whereas most of the arginine formed in PST might contribute, by its conversion to urea, to the process of urine concentration.

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Secretion of prostaglandin E2 by rabbit proximal tubules

AJP Renal Physiology ◽

10.1152/ajprenal.1979.237.4.f268 ◽

1979 ◽

Vol 237 (4) ◽

pp. F268-F273 ◽

Cited By ~ 2

Author(s):

J. M. Irish

Keyword(s):

Prostaglandin E2 ◽

Proximal Tubule ◽

Organic Anion ◽

Passive Movement ◽

Proximal Tubules ◽

Straight Tubule ◽

Luminal Membrane ◽

Cell Accumulation ◽

Proximal Straight Tubule ◽

Anion Transport System

This study was designed to evaluate prostaglandin secretion from bath to urine in isolated perfused rabbit proximal tubules. Active prostaglandin E2 (PGE2) secretion occurred along the entire length of the proximal tubule, but the rate of net secretion was highest in the S2 segment of the proximal straight tubule. Sixteen percent of the PGE2 secreted in the proximal straight tubule was metabolized to other products. The PGE2 cell-to-bath ratio averaged 40 and the tubule fluid-to-bath ratio averaged 3.4. These findings suggest active transport of PGE2 across the peritubular membrane and passive movement across the luminal membrane. Indomethacin, probenecid, para-aminohippurate, and ouabain partially inhibited PGE2 cell accumulation and net secretion. PGE2 entered the urine of the perfused descending limb of Henle (DLH), but at a rate two orders of magnitude below that observed in the S2 segment of the proximal tubule. No evidence of active PGE2 secretion was observed in the DLH. These results suggest that PGE2 is secreted into the urine at substantial rates by the organic anion transport system of renal proximal tubules.

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Endothelin inhibits fluid and bicarbonate transport in part by reducing Na+/K+ ATPase activity in the rat proximal straight tubule.

Journal of the American Society of Nephrology ◽

10.1681/asn.v25976 ◽

1991 ◽

Vol 2 (5) ◽

pp. 976-982

Author(s):

J Garvin ◽

K Sanders

Keyword(s):

Atpase Activity ◽

Proximal Tubule ◽

Flow Rate ◽

Control Period ◽

Bicarbonate Transport ◽

Fluid Absorption ◽

Straight Tubule ◽

Proximal Straight Tubule ◽

Pump Activity

The effects of endothelin on fluid and bicarbonate absorption and Na+/K+ ATPase activity in the proximal straight tubule were investigated. During the control period, fluid absorption was 0.59 +/- 0.03 nL/mm.min when tubules were perfused at 4.76 nL/mm.min. After treatment with 10(-9) M endothelin, fluid absorption fell to 0.36 +/- 0.06 nL/mm.min when perfused at a similar flow rate. During the control period, bicarbonate absorption was 67.9 +/- 3.6 pmol/mm.min. After treatment with endothelin, it fell to 42.8 +/- 4.3 pmol/mm.min, an inhibition of 38%. To test whether inhibition of fluid and bicarbonate absorption was due to suppression of Na+/K+ ATPase activity, the effect of endothelin on pump activity was investigated. In control tubules, Na+/K+ ATPase activity was 85 +/- 5 pmol/mm.min. In endothelin-treated tubules, Na+/K+ ATPase activity was 68 +/- 4 pmol/mm.min, a reduction of 20%. From these data, it was concluded that endothelin inhibits fluid and bicarbonate transport in the proximal tubule and that this inhibition is in part due to suppression of Na+/K+ ATPase activity.

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