0000000000543876
AUTHOR
H. Stolte
Rat proximal tubule D-glucose transport as a function of concentration, flow, and radius
From earlier microperfusion studies ofD-glucose and water reabsorption in the proximal surface nephron of the rat,D-glucose was found to be removed by a saturable carrier and by an apparent coupling with net fluid reabsorption. Equations appropriate to describe this system were developed. They incorporated carrier-mediatedD-glucose transport, net water transport, and water-coupled solute transport. Water reabsorption was assumed to be constant either per unit surface area, or per unit volume of the nephron, and the rate of carrier-transportedD-glucose was assumed constant per unit length, per unit surface area, or per unit volume of the tubule. The possibility thatD-glucose could be reabsor…
D-Glucose and fluid reabsorption in proximal surface tubule of the rat kidney
Hexose reabsorption in the kidney was investigated by microperfusion of proximal cortical rat nephrons with Ringer's solution containingD-glucose (2.5, 5.0 and 18.0 mM/l), 3-O-methylD-glucose (4.5 mM/l) orD-fructose (18.0 mM/l) at perfusion rates of 20 or 40×10−6 ml/min. Inulin was used as a reference for fluid reabsorption. 1. The fraction of fluid reabsorbed was independent of the glucose concentration but it decreased when the perfusion rate increased from 20–40×10−6 ml/min. 2. At 18.0 mM/l the % glucose reabsorption was equal to the % fluid reabsorption. This equality was independent of the perfusion rate, (20 or 40×10−6 ml/min), indicating 1:1 coupling with net isotonic fluid reabsorpt…
Time course of development of transtubular sodium concentration differences in proximal surface tubules of the rat kidney. Micropuncture experiments in intact and adrenalectomized rats.
Int the proximal and distal surface tubules isotonic Na reabsorption (Φ Naout) is impaired by adrenalectomy. In the present experiments the time course of development of transtubular Na concentration differences (Na)P−(Na)TF was studied in the proximal convolution. 1. Na concentration was measured in free flow mannitol diuresis. Endproximal (Na)P−(Na)TF averaged 23.0±0.5 meq/l after 8.5±0.6 sec (controls) and 15.2±1.7 meq/l after 13.6±0.5 sec (adrenalectomized rats). 2. In modified stopped flow experiments tubular fluid, aspirated at the beginning of the proximal convolution in mannitol diuresis, was injected between two oil columnes and reaspirated after 28–36 sec of contact time. (Na)P−(N…