Lipid synthesis by the monoglyceride and α-glycerophosphate pathways in sheep intestine

Abstract

Double-labelled monopalmitin containing ¹⁴C-glycerol and ³H-palmitic acid was used in vitro in intestinal segments and in vivo in intestinal loops of sheep to determine if triglycerides could be synthesized by both the monoglyceride and α-glycerophosphate pathways. Total glyceride synthesis in vitro by the combined pathways was highest in 87- and 120-day foetal lambs, followed in declining order by 6- to 13-day lambs, adult sheep, and adult rats (used for comparative purposes). The minimum percentage of the glycerides synthesized by the monoglyceride pathway using 1-monopalmitin as a precursor was: foetus 20, lamb 29, adult sheep 28, and rat 45. These are minimum values because appreciable hydrolysis of 1-monopalmitin occurred during incubation: 61% in rats, 68% in lambs, 71% in adult sheep, and 80% in foetal sheep. 2-Monopalmitin was more resistant to hydrolysis by intestinal segments and loops and resulted in at least 43% synthesis of glycerides by the monoglyceride pathway in segments of adult sheep intestine, compared to 26% with 1-monopalmitin.