title: Regulation of pathways of ornithine metabolism. Effects of thyroid hormone and diabetes on the activity of enzymes at the "ornithine crossroads' in rat liver.
abstract: There is a significant increase in four of the urea cycle enzymes in liver from hypothyroid rats, arginase alone showed an opposite trend; these changes are reversed by physiological doses of thyroxine; hyperthyroidism results in a significant decrease in ornithine transcarbamoylase activity. The pattern of change in thyroidectomized and alloxan-diabetic rats showed marked similarities in respect to urea cycle and ornithine-metabolizing enzymes which are discussed in the light of the common feature of hypoinsulinism of diabetes and depressed response to insulin in hypothyroidism. The profile of ornithine-metabolizing enzymes is consonant with the decreased protein synthesis and turnover in hypothyroidism.
mesh_terms: D000818:Animals; D002451:Cell Compartmentation; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D006980:Hyperthyroidism / Q000378:metabolism; D008099:Liver / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D008954:Models, Biological; D009952:Ornithine / Q000378:metabolism*; D051381:Rats; D013961:Thyroid Gland / Q000502:physiology*; D013974:Thyroxine / Q000494:pharmacology*; D014508:Urea / Q000096:biosynthesis
chemical_list: D014508:Urea; D009952:Ornithine; D013974:Thyroxine