Effects of Growth Hormone on the Lipolytic Response of Adipose Tissue to Theophylline1

Adipose tissue from hypophysectomized rats has a reduced capacity to carry on lipolysis in response to theophylline and other lipolytic agents. Three hr after a single injection of growth hormone (100 μg), FFA and glycerol production in response to theophylline are increased, but basal lipolysis is unchanged. Preincubation of adipose tissue for 3 hr in the presence of 0.01–1.0 μg/ml of growth hormone significantly increased the lipolytic response to theophylline, again without affecting the basal rate of lipolysis. This action of growth hormone has a lag period of more than 1 hr, is blocked by insulin and augmented by dexamethasone, which has a similar, but less consistent effect. Actinomycin failed to block this response to growth hormone and cycloheximide significantly enhanced it. These data are thought to illustrate an effect of growth hormone on the level of 3′,5′-cyclic AMP in adipose tissue, and suggest a biochemical explanation for the “permissive” effect of growth hormone on lipolysis. (Endocrinology81: 1027, 1968)