Oestradiol inhibits the insulin secretion on the first day of treatment in the ovariectomized rat.

Long term oestradiol treatments stimulate the B cell of the endocrine pancreas. The first effects of oestradiol-17-beta were studied in ovariectomized rats, 16 hours after a subcutaneous injection of various concentrations of this hormone (0, 2.5, 25, 50 micrograms). Plasma oestradiol concentrations, food intake and insulin secretion from islets of Langerhans were measured. Oestradiol always decreased food intake and insulin secretion. However, this inhibiting effect of oestradiol on the B cell was also found in fasted rats. This negative action did not appear on basal insulin secretion but on glucose-induced insulin response. It was characterized by a decrease in the B cell capacity of response to glucose. Short and long term opposite actions of oestradiol on the B cell of the endocrine pancreas could be compared to similar effects shown with glucocorticoids.