Summary
The present experiment was designed to study the action of ACTH1-24 on insulin secretion during the circadian cycle in normal rabbits and to provide
evidence that ACTH1-24 has an extra-adrenal effect on this secretion.
In normal rabbits intravenous administration of three doses of ACTH1-24(1, 10, 100 μg/kg) at 10 a. m. increased plasma insulin levels. Hyperglycemia only
occurred with doses of 10 and 100 μg/kg. A maximum insulin response was already obtained
at 1 μg/kg. The same experiment performed at 12 p. m. also induced hyperinsulinemia
which was only noted at 10 and 100 μg/kg; hyperglycemia was only observed after stimulation
by the highest dose (100 μg/kg). ACTH was therefore more effective during the day;
however, at 12 p. m. plasma insulin levels were the highest, but only with the maximum
dose of ACTH (100 μg/kg).
The effect of ACTH1-24 was evaluated throughout the day on normal and adrenalectomized rabbits. In normal
animals injection of ACTH1-24 increased plasma glucose and insulin levels both together. In the contrary, in rabbits
deprived of adrenal glands, ACTH1-24 induced high insulinemia along with hypoglycemia. We could, therefore, reasonably
conclude that ACTH stimulates directly the pancreatic secretion of insulin.
Key words
Rabbit - Fasting - Adrenalectomy - ACTH1-24
- Insulin - Glucose
