Abstract

To ascertain whether certain gastro-entero-pancreatic hormones whose concentration in blood rises after ingestion of food could play a role in the elevation of plasma triglycerides (or hepatic triglyceride secretion) observed after oral vs parenteral feeding, studies were undertaken of their acute effects upon triglyceride synthesis and release by freshly isolated rat hepatocytes in vitro. The incorporation of radiopalmitate into hepatocyte triglycerides was significantly increased, by one-fourth to one-half, by each of pancreatic polypeptide, peptide YY, and an intermediate concentration (0.50 microgram/mL) of somatostatin. However, at a lower concentration (0.25 microgram/mL) somatostatin significantly decreased (by 14%) the incorporation of radiopalmitate into hepatocyte triglycerides. Release of labelled triglycerides from hepatocytes into the medium was significantly enhanced by both gastric inhibitory polypeptide (by 31%) and pancreatic polypeptide (22%), but was significantly reduced (by 28%) by somatostatin at a concentration of 1 microgram/mL. Neurotensin produced no detectable effect. Although there were similarities between the active hormones, each had a unique overall pattern of response on triglyceride synthesis and release and individually, or in concert with other hormones, could modulate hepatic triglyceride production and secretion, thereby explaining the differential effects of oral vs parenteral feeding on plasma triglycerides.