Effects of dietary protein restriction and glucocorticoid administration on urea excretion in rats.
Rats were sampled for clearance studies under anesthesia after 0, 2, 4, 7 and 14 days of dietary protein restriction. Mean fractional urea excretion decreased between day 2 and day 7 of protein restriction after a two-day lag in response. Seven-day administration of dexamethasone in protein-restricted rats caused a significant increase in mean fractional urea excretion. Adrenalectomized rats fed a normal diet had fractional urea excretion values resembling those in protein-restricted rats. Chronic administration of dexamethasone in adrenalectomized rats caused a consistent increase in fractional urea excretion. Fractional urea excretion values were no lower in protein-restricted adrenalectomized rats fed a normal diet. The mean plasma corticosterone concentration (measured 6 to 8 PM) was decreased in rats fed a low protein diet relative to rats fed a high protein diet. The results suggest that glucocorticoids may play a role in the tubular regulation of urea excretion either by a direct effect on the renal tubule or through some intermediate factor. A mediating role of glomerular filtration rate in glucocorticoid-induced changes of fractional urea excretion could not be ruled out, however.
D000315:Adrenalectomy; D000818:Animals; D003345:Corticosterone / Q000097:blood; D003907:Dexamethasone / Q000494:pharmacology; D004044:Dietary Proteins; D005938:Glucocorticoids / Q000097:blood / Q000494:pharmacology*; D007444:Inulin / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D008297:Male; D051381:Rats; D012965:Sodium Chloride / Q000494:pharmacology; D013997:Time Factors; D014508:Urea / Q000378:metabolism / Q000652:urine*
D004044:Dietary Proteins; D005938:Glucocorticoids; D012965:Sodium Chloride; D003907:Dexamethasone; D014508:Urea; D007444:Inulin; D003345:Corticosterone