Dietary and hormonal regulation of urea cycle enzymes in rat liver.
When 6-week-old rats fed normal diet (22% protein) were transferred to 10 and 75% protein diet, the levels of urea cycle enzymes showed decreases and increases respectively. The activities expressed as units per gram wet weight of liver had not stabilized after 7 days on the new diet; the corresponding specific activities were closer to leveling off. Four daily injections of cortisol raised CPS, ASS, and arginase. The percentage increases were greater on a 10 than on a 75% protein diet. Adrenalectomy of rats fed 10% protein decreased all urea cycle enzymes; on 75% protein, only arginase decreased. All enzymes could be raised to control levels within 24 h by three injections of cortisol. Thyroxine produced only slight increases in urea cycle enzymes. On a 10% protein diet, all five enzymes were raised by thyroidectomy, and further raised by injection of thyroxine.
D000315:Adrenalectomy; D000818:Animals; D001119:Arginase / Q000378:metabolism; D001123:Argininosuccinate Lyase / Q000378:metabolism; D001124:Argininosuccinate Synthase / Q000378:metabolism; D002222:Carbamoyl-Phosphate Synthase (Ammonia) / Q000378:metabolism; D004044:Dietary Proteins / Q000494:pharmacology*; D006854:Hydrocortisone / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D009954:Ornithine Carbamoyltransferase / Q000378:metabolism; D051381:Rats; D013974:Thyroxine / Q000494:pharmacology*; D014508:Urea / Q000378:metabolism*
D004044:Dietary Proteins; D014508:Urea; D009954:Ornithine Carbamoyltransferase; D001119:Arginase; D001123:Argininosuccinate Lyase; D002222:Carbamoyl-Phosphate Synthase (Ammonia); D001124:Argininosuccinate Synthase; D013974:Thyroxine; D006854:Hydrocortisone