Adrenocorticotrophin and the development of insulin secretion in the rabbit foetus

Foetal rabbits were injected with adrenocorticotrophin (ACTH), decapitated, or decapitated and injected simultaneously with ACTH or cortisol in utero on day 24 of gestation. The foetuses were killed after Caesarian section on day 29, and blood was collected for measurement of plasma insulin concentration and pancreatic tissue was obtained for incubation in physiological buffer. Insulin release from the pancreatic tissue of decapitated foetuses was significantly greater than that from the pancreas of control litter-mates when incubated in media containing 3-3mM-glucose, 16-5mM-glucose or 16-5mM-glucose plus 5 mug glucagon/ml, but was similar when the incubation medium contained 3-3 or 16-5 mM-glucose plus 1 mM-theophylline or 3-3mM-glucose plus 60 mM-potassium. The pancreata of decapitated or intact foetuses injected with ACTH did not differ significantly from control foetuses in terms of insulin release in response to glucose in vitro. The plasma insulin concentration of decapitated foetuses and decapitated foetuses injected with ACTH was raised, whereas that of intact foetuses injected with ACTH was similar to that of the control foetuses. Cortisol injection at the time of decapitation resulted in a high rate of foetal mortality. The results indicate that foetal ACTH or foetal adrenocortical secretion influences the normal development of glucose-mediated insulin secretion in the rabbit and that exogenous ACTH corrects the effect of decapitation on beta cell function in vitro but not on plasma insulin concentration.