Pharmacological investigations on the lipolytic and antilipolytic effects of growth hormone (GH) in chicken adipose tissue in vitro: evidence for involvement of calcium and polyamines.

The involvement of RNA/protein synthesis, calcium, calmodulin, protein kinase C, and polyamines in the lipolytic and antilipolytic (inhibition of glucagon-stimulated lipolysis) responses to GH have been investigated employing chicken adipose tissue in vitro. The lipolytic, but not the antilipolytic, effect of GH was blocked by inhibitors of RNA/protein synthesis (actinomycin D, cycloheximide, and puromycin) and calcium uptake (verapamil) and low calcium concentrations (0.28 mM CaCl2). The antilipolytic, but not the lipolytic, effect of GH was blocked by alpha-difluoromethylornithine (DFMO), a polyamine synthesis inhibitor. DFMO-induced blockade of the antilipolytic GH response was reversed by the addition of spermidine. The lipolytic and antilipolytic effects of GH were not influenced by chlorpromazine (a calmodulin inhibitor) or phorbol 12-myristate 13-acetate (PMA) (an activator of protein kinase C).