Free flow micropuncture studies of glucose transport in the rat nephron

Frohnert, Peter P.; Höhmann, Bernhard; R, Zwiebel; Baumann, Karl

doi:10.1007/bf00587238

Cited by 84 publications

(38 citation statements)

References 34 publications

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“…Wen (26) demonstrated that after extracellular volume expansion, fractional and absolute glucose excretions in the final urine were not increased despite a reduction in proximal tubule glucose reabsorption. Similar data has also been reported in the rat (10). It was then suggested that a site distal to the proximal convoluted tubule had the capacity to completely reabsorb the excess distal delivery.…”

Section: Discussionsupporting

confidence: 79%

Maturation of the Glucose Transport Process by the Fetal Kidney

et al. 1978

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Summaryperiod than later in life-suggesting that the tubular function b a s more immature than the-glome;ular function at birth (24). In order to study the maturation the glucose reabsorptive However, Brodehl (6), Baker (4), and Arant (2) were recently process by the fetal kidney, nine chronic fetal lamb Preparations able to demonstrate that the maximal glucose reabsorption per (0.66-3.72 kg) were studied and values compared to data milliliter of glomerular filtrate (Tm JGFR) was equal to or obtained from four nonpregnant ewesand urine control slightly higher than adult levels during the first weeks of life, values showed there was a close relationship between fetal thereby suggesting that glomerular tubular balance was mainglomerular filtration rate (GFR mllmin) and fetal body weight tained, (r = 0-78,P < 0.02). The fractional excretion of sodium, during It has been demonstrated during fetal life in rats (8), pigs control periods, varied from 3.86-14.76%, but no relation with (16), and lambs (1) that the fetal renal tubule reabsorbs glucose.weight Or GFR mi/min was found. The mean Alexander and Nixon (1) suggested that the fetal lamb kidney for blood glucose observed at threshold was higher in the fetus has the capacity to reabsorb most of the filtered glucose before (200 13.3 mg/lOO ml) than in ewes 2.8 mg/lOO the midpoint of gestation, confirming a previous study on the ml). Fetal glucose threshold was correlated to fetal body weight mesonephros of fetal pigs (16). They also demonstrated that (r = 0.71, P < 0.05) and fetal GFR ml/min (r = 0.74, P < phlorizin blocked glucose reabsorption (1). 0.025). r he maximum amount of glucose reabsorbed expressedThese fetal studies (1,8,16), however, were done in acute per GFR (TmJGFR) was reached in One fetus and fetal preparations in which the renal function might have been was 4.73. In fetuses, T m~ was reached since altered considerably by stress and hypoxia (1 1, 20). The present metabolic acidosis developed during the murse of glucose work was designed to study, in chronic fetal sheep preparations, infusion. ow ever, in those fetuses, the highest amount of the maturation of the glucose reabsorptive process by the fetal glucose reabsorbed expressed per unit of GFR (TdGFR), kidney during the last trimester of gestation, before glucose infusion was stopped, varied from 2.32 to 3.85 with a mean of 2.83 -c 0.26. In the adult ewes TmJGFR varied from 1.94 to 2.47, and the mean value (2.21 k 0.12) was MATERIALS AND METHODS significantly lower (P < 0.05) than the mean TmJGFR and T dNine chronic fetal lamb preparations (mixed breed Dorset GFR values found in fetuses. These data indicate that the and Suffolk) and four nonpregnant ewes were used to investigate plasma threshold values for glucose reabsorption by the fetal the renal process of glucose reabsorption. The intrauterine fetal kidney increased with fetal GFR, suggesting that (here is a weight at the time of the experiment was estimated according to parallel development in fetal tubular and glomerular function. the equa...

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Section: Discussionsupporting

confidence: 79%

Maturation of the Glucose Transport Process by the Fetal Kidney

et al. 1978

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“…Thus for a reversible glucose carrier, net movement would be determined by relative, sodium-influenced intraluminal and intracellular affinities for glucose as well as by the transmembrane glucose concentration gradients. It would be predicted that a steady-state intraluminal concentration of glucose would arise in appropriate circumstances, as in the present study and in some previous reports (Rohde & Deetjen, 1968;Frohnert et al 1970;von Baeyer et al 1973). Furthermore, inhibition of such a reversible carrier would be expected to reduce net secretion of glucose, as was found when phlorizin was added to the glucose-free saline perfusate (Table 5).…”

Section: Glucose Secretionsupporting

confidence: 77%

Effects of glucose on water and sodium reabsorption in the proximal convoluted tubule of rat kidney.

Bishop¹,

Green²,

Thomas³

1978

The Journal of Physiology

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SUMMARY1. The effects of glucose on sodium and water reabsorption by rat renal proximal tubules was investigated by in situ microperfusion of segments of proximal tubules with solutions containing glucose or no glucose, with and without phlorizin.2. Absence of glucose did not significantly alter net water flux. Sodium flux was reduced by about 10 % but this was not statistically significant.3. In the absence of glucose in the perfusion fluid net secretion of glucose occurred. 4. Phlorizin reduced either net reabsorption or net secretion of glucose; and net water flux.5. The data suggest that in later parts of the proximal convoluted tubule some sodium may be co-transported with glucose, but that this represents only a small fraction of the total sodium reabsorption.6. It is suggested that the glucose carrier is reversible and in appropriate circumstances could cause glucose secretion.7. Althoughphlorizin alters net water flux the underlying mechanisms are not clear. 8. The calculated osmolality of the reabsorbate was significantly greater than the perfusate osmolality and greater than plasma osmolality although this was not quite significant statistically.

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“…However, there is general agreement over certain observations on transport in the very early postglomerular segment of the superficial proximal convolution (_ the first 15-20% of the convolution). Filtered glucose (28)(29)(30)(31)(32) and amino acids (33)(34)(35)(36)(37) are mostly reabsorbed in the early segment. In addition there is early rapid HCO3 reabsorption (38,39) resulting in a reciprocal rise of the intraluminal Cl concentration.…”

Section: Discussionmentioning

confidence: 99%

Characteristics of Volume Reabsorption in Rabbit Superficial and Juxtamedullary Proximal Convoluted Tubules

Jacobson¹

1979

J. Clin. Invest.

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A B S T R A C T Segments of superficial and juxtamedullary proximal convoluted tubules of the rabbit were perfused in vitro to examine the mechanisms responsible for net volume reabsorption. The very early postglomerular segments were not studied. Fluid reabsorptive rates and transepithelial potential differences were compared under various conditions: (a) with perfusate that simulated glomerular filtrate; (b) with perfusate that lacked glucose, amino acids, and acetate and that had HCO3 and Cl concentrations of 5 and 140 mM, respectively; (c) with perfusate that lacked glucose, amino acids, and acetate but with 20 meq ofNaHCO3 replaced with 20 meq ofNa cyclamate; (d) with the same perfusate as in b but in the presence of ouabain in the bath; (e) with ultrafiltrate of rabbit serum titrated with HC1 to final HCO3 and Cl concentrations of 2 and 134 mM, respectively. Tubules were perfused with this titrated ultrafiltrate at 37°C, 21°C, and in the presence of 0.1 mM ouabain in the bath. Bath fluid in all experiments was regular rabbit serum. Under conditions a and b superficial proximal convoluted tubule (SFPCT) and juxtamedullary proximal convoluted tubule (JMPCT) behaved similarly with the exception that SFPCT exhibited a lumen-positive and JMPCT a lumen-negative electrical potential under condition b. However, undeT condition c SFPCT failed to exhibit net volume reabsorption, whereas reabsorption in JMPCT continued unchanged. Ouabain did not affect volume reabsorption in SFPCT under condition

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Free flow micropuncture studies of glucose transport in the rat nephron

Cited by 84 publications

References 34 publications

Maturation of the Glucose Transport Process by the Fetal Kidney

Maturation of the Glucose Transport Process by the Fetal Kidney

Effects of glucose on water and sodium reabsorption in the proximal convoluted tubule of rat kidney.

Characteristics of Volume Reabsorption in Rabbit Superficial and Juxtamedullary Proximal Convoluted Tubules

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