Oestradiol and insulin secretion in the rat: when does oestradiol start stimulating the insulin release?

Long-term oestradiol treatments induce hyperinsulinism and low glycaemia. Time-related experiments were performed to determine when this effect appears in islets from treated rats. Oestradiol first inhibited the insulin secretion for 2 days and later stimulated the B cells functioning from the 3rd day of treatment onward. This effect of oestradiol was dose-dependent. The beginning of this stimulating action of oestradiol was characterized by a normal tolerance to glucose and normoglycaemia, still maintained in spite of hyperinsulinaemia, hypoglucagonaemia and lowered food intake. This suggested that the long-term oestradiol-induced low glycaemia was a consequence of the hyperinsulinism.