Effect of furosemide on renal handling of glucose in the rat.

Clearance and intratubular microinjection studies were performed in rats during extracellular volume expansion before and after furosemide administration to evaluate renal tubular transport of glucose. Three groups of animals were studied: group I, intact rats; group II, acutely thyroparathyroidectomized rats; and group III, thyroparathyroidectomized rats receiving parathyroid extract after a control period. In all groups furosemide caused a significant increase in the urinary flow rate and sodium excretion. There was no significant change in filtered glucose and glucose excretion. After early distal tubular injections of [14C]glucose, recovery was complete both before and after furosemide infusion. Furosemide had no effect on [14C]glucose recovery after the late proximal injection. These results indicate that furosemide has no effect on the renal handling of glucose in normoglycemic rats. There is no evidence for glucose reabsorption in the nephronal segments distal to the early distal tubular segment in this experimental state. Our data suggest, but do not prove, that no glucose is transported by the rat nephron beyond the pars recta during normoglycemia.