Metabolism of [U-14C; 2,3-3H]-L-valine by the isolated perfused goat udder.
Two lactating mammary glands excised from 2 goats were perfused for several hours in the presence of [U-14C; 2,3-3H]-L-valine and received adequate quantities of glucose, acetate and amino acids. In the synthesized milk 96 and 89% respectively of the casein valine was derived from free plasma valine. Valine was extensively catabolized by mammary tissue, resulting in a considerable 14CO2 production and in the incorporation of 14C into milk citric acid and to a lesser extent into casein aspartic acid and glutamic acid. About 30% of the valine molecules which were taken up by the mammary gland were oxidized to CO2 and 70% were incorporated in casein as valine residues. About 10% of the plasma valine molecules were reversibly transaminated during one passage through the udder. An important amount of radioactivity of plasma was present in unknown metabolites. Only 7% of this activity was localized in isobutyrate. The radioactivity of total milk fat was very low. Mainly iso-14:0, iso-16:0 and 15:0 were labelled.
D000818:Animals; D002364:Caseins / Q000096:biosynthesis; D006041:Goats / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D008321:Mammary Glands, Animal / Q000378:metabolism*; D010477:Perfusion; D014280:Triglycerides / Q000378:metabolism; D014633:Valine / Q000097:blood / Q000378:metabolism*
D002364:Caseins; D014280:Triglycerides; D014633:Valine