Influence of adenosine or adrenergic agonists on growth hormone stimulated lipolysis by chicken adipose tissue in vitro.

In vitro lipolysis by chicken adipose explants was stimulated by growth hormone (GH) or glucagon. Adenosine or the adenosine agonist, N6-phenylisopropyladenosine (PIA), inhibited GH stimulated lipolysis, the effect of adenosine not being observed in the presence or adenosine deaminase. Glucagon induced lipolysis was also reduced by PIA. It is suggested that adenosine may act by Gi linked to either adenylate cyclase (for glucagon) or the signal transduction mechanism for GH. Lipolysis was not stimulated by GH in the presence of phenylephrine (alpha 1 adrenergic agonist), isoproterenol (beta adrenergic agonist), adrenaline or glucagon. Although the presence of p-amino clonidine (alpha 2 adrenergic agonist) depressed basal lipolysis, a response to GH was still present. Either glucagon or beta-adrenergic agonists (isoproterenol, adrenaline) stimulated lipolysis. In both cases, GH attenuated the lipolytic response to these hormones, which act via a cyclic adenosine monophosphate signal transduction mechanism.