Effects of nutritional status and the pituitary on the acute plasma free fatty acid and glucose responses of rats to growth hormone administration

Abstract

Normal and hypophysectomized rats, either in the fed or fasted state, were treated with bovine growth hormone (BGH) to determine whether the acute decline in plasma free fatty acids (FFA) and glucose in response to growth hormone (GH) administration could be modified by nutritional status and the presence of the pituitary. Both 1- and 3-mg. doses of BGH caused a plasma FFA diminution at 30 and 22 minutes, respectively, in hypophysectomized rats fasted for 24 hours. The hypolipemia observed with either dose of BGH was associated with an early fall in plasma glucose. The plasma glucose, however, did not subsequently return to normal levels during the 1-hour experimental period, as was the case with plasma FFA. At the higher dose of BGH plasma, FFA were markedly elevated above control levels at 1 hour, a condition indicative of the well-documented, secondary, hyper-lipemic response to GH treatment. The acute hypolipemic and hypoglycemic responses to BGH were not altered when hypophysectomized rats were used following a 42-hour fast. Hypophysectomized rats, which were not fasted, however, only exhibited the hypoglycemic response to BGH treatment; no alterations in plasma FFA levels were observed in these animals. Normal rats, either fed or fasted, showed neither the decline in plasma FFA nor of glucose following treatment with BGH. The time course of the acute hypolipemic and hypoglycemic effects of BGH in rats, when determined under the appropriate conditions of hypophysectomy and fasting, were further demonstrated to be functions of the preparation of BGH used.