Physiologic release of secretin measured in peripheral and portal venous blood of dogs.

The effect of food on circulating levels of secretin, measured by radioimmunoassay, was studied in 7 dogs. Significant postprandial increases in secretin were found in portal and peripheral plasma of dogs fasted for 18 h. Basal levels of secretin were significantly lower in dogs fasted for 72 h when compared with dogs after an 18-hour fast. After the prolonged fast, food caused a significant release of secretin, measured peripherally. We conclude that secretin is released by a physiologic stimulus (food) and that circulating levels of secretin are depressed after prolonged starvation.