Pathways of Triglyceride Synthesis by Bovine Jejunum During Lipid Absorption

Abstract

Pathways of triglyceride synthesis were investigated in bovine intestine by incubating three different micellar substrates, each containing 1-monoolein and oleic acid with mid-jejunal sections, and by incubating jejunal microsomes with substrate mixtures containing either monoolein or α-glycerophosphate. Cattle in the experiment received either a milk or a hay-grain diet. Both dietary groups had the capacity to resynthesize triglycerides by either the monoglyceride or the α-glycerophosphate pathway. Diet had no effect on the percentage of triglyceride synthesized by the monoglyceride pathway despite the fact that cattle receiving a hay-grain diet had little or no monoglyceride passing into the small intestine. Jejunal tissue from cattle receiving hay-grain synthesized more triglyceride than did jejunal tissue from animals receiving milk, but tiglyceride synthesis by isolated microsomes was not different between groups. With jejunal sections, apparent participation of monoglyceride pathway in triglyceride synthesis was approximately 80% when the substrate contained no α-glycerophosphate precursors, 50% when the substrate contained glucose, and 30% when both glucose and glycerol were present. With microsomes, triglyceride was synthesized at approximately equal rates for both pathways. Thus, milk-fed calves possess monoglyceride pathway activity, and enzymes for this pathway are retained in older cattle fed hay and grain. © 1973, American Dairy Science Association. All rights reserved.