The effect of somatostatin on fasting and postprandial plasma GIP, serum insulin, and blood glucose in man.

Six healthy men were given a standard breakfast, one day with and another day without a 2-h 100 micrograms/h somatostatin infusion. During the somatostatin infusion the meal-induced responses of plasma GIP and serum insulin were completely blocked, whereas the rise in blood glucose was significantly augmented. After termination of the somatostatin infusion the mean plasma GIP increased gradually to a peak after 2 h, whereas mean serum insulin showed a marked rebound phenomenon and peaked after 30 min, on the one hand, and mean blood glucose fell to an apparent nadir after another 30 min, on the other. The effect of somatostatin on basal plasma GIP, serum insulin, blood glucose, and gastric H+ secretion was studied in another group of six healthy men. Mean plasma GIP tended to fall during the initial 1-h saline infusion, fell further during the first part of the 2-h 100 micrograms/h somatostatin infusion, and started to rise first 85 min after termination of the somatostatin infusion. Similarly, mean serum insulin, mean blood glucose, and mean gastric H+ secretion decreased during the somatostatin infusion, and thereafter returned to their basal levels.