Hormonal Control of Biliary Lipid Secretion in Dogs

Five dogs were anesthetized, their cystic ducts were ligated, and their common bile ducts cannulated. The experiments were divided into four 1-hour periods. Taurocholic acid (18 mumol/min) and pipenzolate methylbromide (0.5 mg/kg body weight initially followed by 0.1 mg/kg body weight/20 minutes) were infused during all periods. Somatostatin (800 ng/kg/min) was infused during periods 2, 3, and 4 to suppress the endogenous secretion of peptide hormones. During periods 3 and 4, insulin was infused into a mesenteric vein at rates of 0.2 mU/kg/min and 0.8 mU/kg/min, respectively. These rates have been shown to produce fasting and postprandial portal vein insulin levels. Bile was collected during each period and the volume, bile acid concentration, and biliary lipid content were measured. Another five dogs were studied in a similar way, except that glucagon was infused in place of insulin at rates of 0.6 and 3.0 ng/kg body weight/min to produce fasting and postprandial portal vein levels. The results show that 1) the biliary secretion of cholesterol and phospholipid is increased by pharmacologic doses of somatostatin and 2) physiologic doses of glucagon, but not insulin , suppress the biliary secretion of cholesterol and phospholipid.