EFFECT OF SECRETIN ON BILE FORMATION IN SHEEP

The rate of flow of bile increased rapidly when pure natural secretin was infused into the portal vein of conscious, standing sheep. The increment in flow was related significantly to the logarithm of the rate of administration but was not affected by the simultaneous infusion of sodium taurocholate into the portal vein. When secretin and taurocholate were given together the rate of flow of bile was five times that during the control period of bile salt deprivation. Secretin stimulated the secretion of total fatty acids into the bile of sheep when they were deprived of recirculated bile salts and also when they received an infusion of taurocholate into the portal vein. The mean maximum rate of total fatty acid secretion was 38 per cent higher during infusion of secretin with taurocholate than during infusion of taurocholate alone. When taurocholate was infused into the portal vein at 37 µumole/min or less, it was transferred quantitatively into the bile, and secretin did not appear to affect this process. However, when taurocholate was infused alone at 112 µmole/min it was not transferred quantitatively into the bile, but the efficiency of this transfer was increased by the simultaneous infusion of secretin. The concentration in the bile of total fatty acids and of bile salts decreased during infusion of secretin, but no significant changes occurred in the concentration of sodium. The infusion of secretin caused no significant changes in the osmolality of the bile in five sheep, but in three experiments on a sixth sheep it caused a highly significant increase in osmolality. When secretin was infused into the portal vein, no changes occurred in the arterial pressure, pulse rate, portal venous pressure or respiratory rate. These experiments indicate that secretin could play a significant role in regulating bile secretion in the sheep.