Renal excretion of urate in mongrel and Dalmatian dogs: a micropuncture study

Free-low micropunction experiments were performed in mongrel dogs and in Dalmatian coach hounds infused with urate to obtain Purate levels of 0.15-0.21 mM before and during the infusion of pyrazinioc acid (PZA). In the absence of PZA, mongrel dogs excreted approximately 50% and Dalmatians 140% of filtered loads of urate. In mongrel dogs net reabsorption occurred only in the proximal convoluted tubules. PZA enhanced net proximal reabsorption and revealed the occurrence of proximal secretion, whereas fractional urate excretion in the urine decreased only slightly. In Dalmation dogs urate fluxes across walls of proximal convoluted tubules resulted in either net reabsorption or net secretion, with no mean change. Net urate secretion occurred between superficial late-proximal and early-distal tubules, and considerably decreased fractional excretion of urate. The renal handling of PZA was similar in mongrel and in Dalmatian dogs.

Download Full-text

Effects of furosemide or acetazolamide infusion on renal handling of lithium: a micropuncture study in rats

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1993.264.1.r129 ◽

1993 ◽

Vol 264 (1) ◽

pp. R129-R134 ◽

Cited By ~ 3

Author(s):

R. Fransen ◽

W. H. Boer ◽

P. Boer ◽

E. J. Dorhout Mees ◽

H. A. Koomans

Keyword(s):

Concentration Ratio ◽

Thick Ascending Limb ◽

Renal Handling ◽

Pars Recta ◽

Micropuncture Study ◽

Convoluted Tubules ◽

Filtered Load ◽

Proximal Convoluted Tubules

Renal lithium (Li) handling was studied by micropuncture at the late proximal (LPT) and early distal (EDT) tubules in control rats and rats infused with furosemide (FUR) or acetazolamide (ACTZ). In control rats, the tubular fluid-to-plasma Li concentration ratio [(T/P)Li] at the LPT exceeded unity (1.05 +/- 0.02, P < 0.05). Some 25% of the filtered load (FL) of Li and water was reabsorbed in proportion between the LPT and the EDT, and consequently the (T/P)Li at the EDT (1.03 +/- 0.03) did not change. FUR inhibited Li reabsorption in the proximal convoluted tubules (PCT), by approximately 7% of the FL. Reabsorption of Li and water in the loop segment was also inhibited, virtually in proportion, by approximately 10% of the FL. These data suggest that FUR-sensitive Li reabsorption in the loop mainly takes place in the pars recta. However, a small increase in the (T/P)Li at the EDT (to 1.10 +/- 0.01) suggested inhibition of some Li transport (approximately 2% of the filtered load of Li) without water, most likely in the thick ascending limb (TAL). In the PCT, ACTZ reduced Li reabsorption by approximately 16% of its FL. Although it is likely that ACTZ also inhibited the pars recta, net Li reabsorption in the loop was not reduced. This suggests that TAL Li reabsorption can compensate for increased delivery.(ABSTRACT TRUNCATED AT 250 WORDS)

Download Full-text

Cellular and subcellular localization of enzymes of arginine metabolism in rat kidney

Biochemical Journal ◽

10.1042/bj2820369 ◽

1992 ◽

Vol 282 (2) ◽

pp. 369-375 ◽

Cited By ~ 43

Author(s):

S N Dhanakoti ◽

M E Brosnan ◽

G R Herzberg ◽

J T Brosnan

Keyword(s):

Rat Kidney ◽

Subcellular Fractionation ◽

Kidney Cortex ◽

Ornithine Aminotransferase ◽

Outer Medulla ◽

Argininosuccinate Synthase ◽

Distal Tubules ◽

Convoluted Tubules ◽

Inner Cortex ◽

Proximal Convoluted Tubules

Rat kidneys extract citrulline derived from the intestinal metabolism of glutamine and convert it stoichiometrically into arginine. This pathway constitutes the major endogenous source of arginine. We investigated the localization of enzymes of arginine synthesis, argininosuccinate synthase and lyase, and of breakdown, arginase and ornithine aminotransferase, in five regions of rat kidney, in cortical tubule fractions and in subcellular fractions of cortex. Argininosuccinate synthase and lyase were found almost exclusively in cortex. Arginase and ornithine aminotransferase were found in inner cortex and outer medulla. Since cortical tissue primarily consists of proximal convoluted and straight tubules, distal tubules and glomeruli, we prepared cortical tubule fragments by collagenase digestion of cortices and fractionated them on a Percoll gradient. Argininosuccinate synthase and lyase were found to be markedly enriched in proximal convoluted tubules, whereas less than 10% of arginase and ornithine aminotransferase, were recovered in this fraction. Arginine production from citrulline was also enriched in proximal convoluted tubules. Subcellular fractionation of kidney cortex revealed that argininosuccinate synthase and lyase are cytosolic. We therefore conclude that arginine synthesis occurs in the cytoplasm of the cells of the proximal convoluted tubule.

Download Full-text

OCCURRENCE OF PHAGOSOMES AND PHAGO-LYSOSOMES IN DIFFERENT SEGMENTS OF THE NEPHRON IN RELATION TO THE REABSORPTION, TRANSPORT, DIGESTION, AND EXTRUSION OF INTRAVENOUSLY INJECTED HORSERADISH PEROXIDASE

The Journal of Cell Biology ◽

10.1083/jcb.21.3.295 ◽

1964 ◽

Vol 21 (3) ◽

pp. 295-308 ◽

Cited By ~ 125

Author(s):

Werner Straus

Keyword(s):

Horseradish Peroxidase ◽

Foreign Protein ◽

Outer Cortex ◽

Size Number ◽

Peritubular Capillaries ◽

Distal Tubules ◽

High Doses ◽

Collecting Tubules ◽

Convoluted Tubules ◽

Proximal Convoluted Tubules

The size, number, and location of lysosomes, phagosomes, and phago-lysosomes in different segments of the proximal and distal tubules, in the collecting tubules, and in invading macrophages of the kidneys of rats were compared by staining lysosomes (acid phosphatase) red, and phagosomes (injected horseradish peroxidase) blue in separate sections, and by staining phago-lysosomes purple by successive application of the reactions for the two enzymes in the same sections. It was concluded from these observations that the absorption of the foreign protein from the lumen and its gradual digestion in large phago-lysosomes took place mainly in the cells of the proximal convoluted tubules of the outer cortex. Several segments of the proximal convoluted tubules were distinguished on the basis of differences in the size and location of the phago-lysosomes and the amounts of peroxidase ingested. The distal tubules showed, in addition to moderate numbers of phago-lysosomes, many small phagosomes in the apical and basal zones of the cells. Moderate numbers of phagosomes and phago-lysosomes were observed in the cells of the collecting tubules. Macrophages showing very large phago-lysosomes were seen in the peritubular capillaries of the medulla, after injection of peroxidase. When high doses of peroxidase were administered, enlarged phago-lysosomes, parts of which seemed to be extruded into the lumen, were formed in the terminal segments of the proximal convoluted tubules.

Download Full-text

Renal excretion of ascorbic acid in the rat: a micropuncture study

AJP Renal Physiology ◽

10.1152/ajprenal.1983.244.3.f335 ◽

1983 ◽

Vol 244 (3) ◽

pp. F335-F341

Author(s):

M. Martin ◽

B. Ferrier ◽

F. Roch-Ramel

Keyword(s):

Ascorbic Acid ◽

High Performance ◽

Renal Excretion ◽

Fractional Excretion ◽

Proximal Convoluted Tubule ◽

Drug Induced ◽

Micropuncture Study ◽

Ascorbate Concentration ◽

Secretory Transport ◽

Steady State Levels

Ascorbate concentration was measured by high-performance liquid chromatography and amperometry in plasma, tubular fluid, and urine from rats infused with ascorbic acid to steady-state levels. At a low concentration of ascorbate in plasma (Pasc = 0.2 mM) reabsorption occurred along the proximal convoluted tubule (PCT). The fractional delivery (FD) of ascorbate [(TF/P)asc/(TF/P)polyfructosan] to the late proximal convoluted tubule was 0.64 +/- 0.04, and the fractional excretion of ascorbate (FEasc) was 0.56 +/- 0.01. At higher Pasc (0.9 mM) net secretion occurred in the PCT, while the FDasc was 1.5 +/- 0.2 to the early and 1.8 +/- 0.2 to the late PCT. At still higher Pasc the secretory and the reabsorptive transports were saturated and the FDasc and FEasc approached unity, indicating that reabsorptive as well as secretory transport occurs in the proximal tubule. In clearance experiments the reabsorptive transport and secretory transport were inhibited by 2-nitroprobenecid. The drug induced a fall of FEasc when infused at a low rate (0.9 mumol X kg body wt-1 . min-1), which was followed by an increase in FEasc when the rate of infusion of 2-nitroprobenecid was increased to 3 mumol . kg body wt-1 X min-1.

Download Full-text

Phosphate transport in superficial and deep nephrons in phosphate-loaded rats

AJP Renal Physiology ◽

10.1152/ajprenal.1977.233.2.f150 ◽

1977 ◽

Vol 233 (2) ◽

pp. F150-F153 ◽

Cited By ~ 2

Author(s):

F. G. Knox ◽

J. A. Haas ◽

T. Berndt ◽

G. R. Marchand ◽

S. P. Youngberg

Keyword(s):

Wistar Rats ◽

Fractional Excretion ◽

Phosphate Transport ◽

Loop Of Henle ◽

Phosphate Loading ◽

Distal Tubules ◽

Fractional Excretion Of Phosphate ◽

Convoluted Tubules ◽

Superficial And Deep Nephrons ◽

Collecting System

We tested the hypothesis that greater phosphate delivery from deep nephrons than from superficial nephrons contributes to the addition of phosphate to the collecting system during phosphate loading. In the first group of eight anesthetized Munich-Wistar rats infused with phosphate and parathyroid hormone (PTH), fractional delivery of phosphate (FDP%) from superficial distal tubules was 56 +/- 6%, significantly less than the amount appearing in the urine, 67 +/- 6% (P less than 0.01). In the second group of six rats, we determined whether this addition of phosphate could be accounted for by a higher FDP% from the deep nephrons. Free-flow micropuncture collections were taken from deep nephrons (ascending limb of the loop of Henle in the papilla), superficial nephrons (distal tubules in the cortex), and urine (duct of Bellini). The FDP% to the ascending limb of the loop of Henle in deep nephrons was 78 +/- 10%, significantly greater than to the distal convoluted tubules in superficial nephrons, 51 +/- 6% (P less than 0.005), and the fractional excretion of phosphate in urine, 72 +/- 10% (P less than 0.05). Although a difference between FDP% in superficial and deep nephrons due to reabsorption in the ascending limb of the loop of Henle cannot be ruled out from the present data, other studies indicate that this interpretation is unlikely. We conclude that greater phosphate delivery by deep nephrons contributes to the addition of phosphate to the collecting system of phosphate-loaded rats.

Download Full-text

Micropuncture study of renal excretion of water, K, Na, and Cl in Necturus

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1962.203.4.662 ◽

1962 ◽

Vol 203 (4) ◽

pp. 662-666 ◽

Cited By ~ 29

Author(s):

Phyllis A. Bott

Keyword(s):

Renal Excretion ◽

Distal Tubule ◽

Sodium Concentration ◽

Great Variability ◽

Proximal Tubules ◽

Kidney Tubules ◽

Sodium Potassium ◽

Micropuncture Study ◽

Distal Tubules

Inulin, sodium, potassium, and chloride were determined on identical samples of serum and fluid collected from the kidney tubules of Necturus under urethan anesthesia. Inulin fluid-serum ratios obtained were as follows: highest ratios for proximal tubules approximated 2, indicating a reabsorption of about 50%, of filtered water; highest ratios for distal tubules were near 3.4; ratios for sodium remained near 1 in proximal tubules, tending to be lowest near the ends of the segments. There was an abrupt drop in sodium concentration in the early part (thin segment) of the distal tubules, which may be made possible by the better oxygen supply in this region. Chloride ratios rose to 1.12 in the proximal tubules and chloride concentrations fell over the same region, as did sodium. Potassium ratios remained close to 1 in the proximal tubules, indicating that up to one-half of the filtered potassium may be reabsorbed there. Distal tubule potassium ratios showed great variability, some being higher and some lower than 1.

Download Full-text