THE EFFECT OF FASTING AND GLUCOSE LOAD ON INSULIN SECRETION AND THE STAUB—TRAUGOTT PHENOMENON IN PIGS

Abstract

SUMMARY Pigs were fasted for 18, 39, or 72 h; they were then given two glucose infusions, the second infusion 40 min after the first. Either 0·15, 0·30 or 0·75 g glucose/kg were given at each infusion. Plasma glucose, free fatty acids, insulin and 3-hydroxybutyrate concentrations were measured. The rate of glucose removal Kt was calculated after the first infusions, (Kt1), and after the second infusion (Kt2). When food was withheld the peak insulin concentration decreased in response to glucose but lack of food only affected the mean increase in insulin concentration when 0·75 g glucose/kg was given. The value of Kt1 decreased as the period without food increased and additions of insulin did not affect the difference in Kt1 between animals fasted for 18 h and those fasted for 72 h. Plasma insulin concentration was closely related to the rate of glucose removal; the correlation coefficient (r) for maximum rate of glucose removal versus maximum insulin concentration was 0·9; and that for mean rate of glucose removal versus mean increment in insulin concentration was 0·84. It is suggested that insulin does not itself determine the rate of glucose removal but is secreted in response to the amount of glucose removed. In the pig, the Staub—Traugott phenomenon was found to occur only under special circumstances. The relationship between Kt1 and Kt2 depended on the amount of glucose infused and the time during which food was withheld. Kt2 ranged from smaller than—through the same as—to greater than Kt1. The concentrations of free fatty acids, ketones or insulin did not explain the differences.