POST-FEEDING LEVELS OF INSULIN AND GLUCAGON IN TROUT (SALMO-TRUTTA-FARIO)

1. Insulin, glucagon and plasma glucose levels were studied during the post-feeding period in juvenile brown trout (Salmo trutta fario). Three experiments were performed, in June, July and October, with animals weighing 60.0 +/- 0,9 g, 102 +/- 2.6 g and 177.5 +/- 5.9 g respectively, with sequential samplings between 1 and 24 hr after feeding. 2. Plasma insulin levels reached maximum values within 2 hr after feeding (range of values, 9.4 +/- 1.2 ng/ml to 14.1 +/- 0.9 ng/ml). Insulin then started to decrease gradually but remained high for 11 hr. At 24 hr post-feeding insulin levels ranging from 4.0 +/- 0.4 ng/ml to 7.6 +/- 0.6 ng/ml were observed. No seasonal differences were found in the post-feeding profiles of plasma insulin. 3. Glucagon also increased rapidly but was depressed at 2 or 5 hr (depending on the experiment) simultaneously with high insulin. Glucagon maximum levels (ranging from 1779.1 +/- 182.3 pg/ml to 2261.3 +/- 253.5 pg/ml) were observed when insulin decreased, reaching values at 24 hr ranging from 638.2 +/- 82.1 pg/ml to 857 +/- 65.2 pg/ml. Glucose showed a similar tendency to that of glucagon, with an initial fall and later recovery at 8 or 11 hr.