Decreased proliferation of pituitary cells of streptozotocin-induced diabetic rats in response to estradiol-17-beta.

Insulin is involved in the proliferation of fibroblasts, hepatocytes and certain other lines of cultured cells. In the present study an attempt was made to clarify the role of insulin in the proliferation of rat pituitary cells. Adult male rats of the Wistar/Tw strain were given intraperitoneal injections of streptozotocin (STZ) at a dose of 32.5 mg/kg. STZ-treated rats developed high blood glucose levels and low serum insulin levels. Proliferation of cells was examined by monitoring the cell uptake of bromodeoxyuridine (BrdU). Estradiol-17 beta (50 micrograms) was given to stimulate the proliferation of pituitary cells. The number of BrdU-containing cells was lower in STZ-treated rats than in controls. The responsiveness to estrogen in terms of cell proliferation was lower in STZ-treated rats than in controls. Treatment of STZ-treated rats with insulin increased the number of BrdU-containing cells and restored the responsiveness to estrogen. Insulin stimulated the proliferation of prolactin-secreting cells and growth hormone-secreting cells in estrogen-treated rats. These results suggest that insulin is necessary for the proliferation of pituitary cells.