INHIBITION OF LIPOLYSIS IN HAMSTER EPIDIDYMAL ADIPOCYTES BY SELECTIVE ALPHA-ADRENERGIC AGENTS - EVIDENCE FOR CYCLIC AMP-DEPENDENT AND INDEPENDENT MECHANISMS

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  • 1 January 1979
    • journal article
    • research article
    • Vol. 587  (2) , 217-226
Abstract
The role of cyclic[c]AMP in the antilipolytic effect of the .alpha.-adrenergic agents methoxamine and phenylephrine in hamster epididymal adipocytes was studied. Both methoxamine and phenylephrine lowered the very high levels of cAMP that were produced by high concentrations of isoproterenol (10 .mu.M) or ACTH (100 mU[milli units]/ml), and partially inhibited lipolysis. When lower concentrations of isoproterenol were used, the antilipolytic effect of phenylephrine and methoxamine was evident. Under these conditions methoxamine produced a slight suppression of cAMP levels while phenylephrine increased accumulation of cAMP. Apparently inhibition of lipolysis by the .alpha. agents probably unrelated to changes in cAMP levels. When the stimulus for lipolysis was provided by methylxanthines a different picture emerged. Methoxamine antagonized lipolysis and lowered cAMP levels; but phenylephrine promoted lipolysis and increased cAMP levels. In the presence of propranolol, phenylephrine lowered cAMP levels and suppressed methylaxanthine-accelerated lipolysis. Apparently when methylxanthines provide the stimulus for lipolysis the antilipolytic effect of methoxamine and phenylephrine (in the presence of propranolol) may be mediated by the suppression in cAMP levels.