Effect of alterations in blood sugar on pituitary growth hormone content in the rat.

Abstract

Pituitary growth hormone (GH) content was estimated by the tibial epiphysial cartilage test in hypophysectomized rats. The intraperitoneal (ip) injection of 1 U/kg of regular insulin evoked a profound hypoglycemia. This was accompanied by a fall in the GH activity of the pituitary at 1 hr after injection of insulin. Pituitary GH had returned to normal levels at 3 and 7 hr after injection even though blood sugar was still low. By contrast the ip administration of hypertonic or isotonic glucose produced elevations in both blood sugar and pituitary GH. Injection of glucagon subcutaneously (sc) at a dose of 50 μg also elevated blood sugar and pituitary GH activity. Administration of α-2-Ddeoxyglucose at a dose which elevated blood glucose was followed by a fall in pituitary GH, whereas 50 μg of epinephrine in oil given intramuscularly (im) produced a fall in GH activity followed by a rise even though blood sugar was elevated throughout. It was concluded that alterations in available glucose influence the secr...