Maturation of the Glucose Transport Process by the Fetal Kidney

Abstract

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...

The Dynamics of Vasopressin Release and Blood Volume Regulation During Fetal Hemorrhage in the Lamb Fetus

“…In all fetuses, the chronic indwelling catheter preparation was used as previously described (29). Briefly, under halothane anesthesia, polyethylene catheters were passed into the fetal femoral artery and vein.…”

Developmental Aspects of Renal β-Amino Acid Transport. IV. Brush Border Membrane Response to Altered Intake of Sulfur Amino Acids

“…The reduction in the maximal tubular reabsorption of glucose found in the immature kidney has been known since the late 1940s (38). Although Tudvad (38) felt that the maximal reabsorption was reduced even for the low glomerular filtration rate of infants, recent studies have indicated that the maximal glucose reabsorption per milliliter of glomerular filtrate is equal to adult levels during infancy in man (5), in dog (I), and in sheep, even during the fetal period (29). Preliminary studies in BBMV in newborn rabbit (8) and guinea pig (34) indicate that the V,,, of uptake of D-glucose is lower than in adults.…”

“…Positive effects were attributed to a reduction in systemic vascular impedance or left ventricular afterload caused by arteriolar vasodilatation and to a reduction in preload secondary to venodilatation (29). Reduction in preload, however, can also result from the additional effects of nitroprusside on myocardial relaxation ( 6 ) , left ventricular diastolic properties (7), and alterations in pulmonary venous compliance (32).…”

Congenital urinary tract obstruction: defining markers of developmental kidney injury

“…No normative data are available for fetal urine and amniotic fluid concentrations of potassium, phosphate, calcium, amino acids, glucose, magnesium, and organic acids. However, the somatic growth of the fetus requires positive potassium and phosphate balance (42), and this is reflected in the lower fractional excretions of these solutes in newborns as compared to children and adults (43,44).With advancing gestational age, calcium, amino acid, and glucose excretion decrease, while magnesium and organic acid excretion increase, reflecting maturation of the relevant solute-specific transporters (45)(46)(47).…”