Comparison of transcellular and transepithelial water osmotic permeabilities (P os) in the isolated proximal straight tubule (PST) of the rabbit kidney

1988 ◽  
Vol 412 (1-2) ◽  
pp. 66-74 ◽  
Author(s):  
Paola Carpi-Medina ◽  
Guillermo Whittembury
Keyword(s):  
Rabbit Kidney ◽  
Straight Tubule ◽  
Proximal Straight Tubule

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

1991 ◽  
Vol 260 (5) ◽  
pp. F757-F763 ◽  
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.

Potassium secretion in the rabbit proximal straight tubule

1983 ◽  
Vol 245 (2) ◽  
pp. F167-F174 ◽  
Author(s):  
A. G. Wasserstein ◽  
Z. S. Agus
Keyword(s):  
Rabbit Kidney ◽  
Renal Handling ◽  
Straight Tubule ◽  
Proximal Straight Tubule ◽  
Proximal Tubular ◽  
K Secretion ◽  
Luminal Flow ◽  
Potassium Secretion ◽  
K Concentration

The renal handling of potassium is generally thought to involve proximal reabsorption and distal secretion. To evaluate transport in the pars recta, we perfused S2 and S3 segments from superficial and juxtamedullary proximal straight tubules isolated from the rabbit kidney. The data indicate net potassium secretion in the isolated perfused perfused proximal straight tubule (PST). K+ secretion (JK, pmol X mm-1 X min-1) was -2.51 +/- 0.53 in superficial PST S2 segments, -2.80 +/- 1.05 in superficial PST S3 segments, and -1.36 +/- 0.84 in juxtamedullary PST. Secretion was inhibited by 10(-5) M ouabain in the bath in superficial S2 and S3 segments. When a solution resembling late proximal tubular fluid was perfused in superficial PST, JK fell from -3.86 +/- 1.77 to -0.45 +/- 0.63 pmol X mm-1 X min-1. When luminal flow rate was varied in the physiologic range in individual superficial S2 and S3 segments, JK varied directly; K+ secretion increased by -0.5 pmol X mm-1 X min-1 per 1 nl X min-1 increment in luminal flow, while collected K+ concentration did not vary significantly. When a favorable bath-to-lumen K+ gradient (10 vs. 5 mM) was imposed, K+ secretion was markedly enhanced; when an equal but oppositely directed gradient was imposed, net K+ reabsorption was observed. These data are consistent with a gradient-limited process. In midcortical tubule segments (S2 and S3), 10(-3) M amiloride in perfusate inhibited net K+ secretion from -2.77 +/- 0.52 to -0.18 +/- 1.08 pmol X mm-1 X min-1 and fluid absorption from 0.42 +/- 0.10 to 0.18 +/- 0.05 nl X mm-1 X min-1. Net K+ secretion in S2 and S3 segments of PST may contribute to previously reported K+ secretion prior to the bend of Henle's loop. The magnitude of this process in vivo is uncertain in the absence of measurements of interstitial K+ concentration in the milieu of the PST.

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.

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.

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.

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