Regulation of immunoreactive growth hormone secretion in male rats.

Abstract

Plasma GH levels of fed male gentled rats (52+6 ng/ml) were significantlygreater than those of nongentled animals (24 + 5 ng/ml). Plasma corticosterone levels showed the opposite relationship—gentled, 4.6 ± 0.8 μg/100 ml, vs. nongentled, 8.4 ± 1.4 μg/100 ml. Pentobarbital anesthesia caused a significant rise in plasma GH in both gentled and nongentled rats and a corresponding decrease in plasma corticosterone. A statistically significant diurnal variation in plasma GH could not be demonstrated, although the lowest GH levels were generally observed at 5 PM and corresponded to peak values for plasma corticosterone. Ether anesthesia, hypertonic glucose, 2-deoxyglucose, insulin-induced hypoglycemia and epinephrine all resulted in a marked suppression of plasma GH, and an increase in plasma corticosterone, effects which were either partially or completely blocked by pentobarbital anesthesia. The effects of insulin-induced hypoglycemia and 2-deoxyglucose were not mediated by catecholamines since they were noted...