ENHANCED ORNITHINE DECARBOXYLASE ACTIVITY OF CHICK MUSCLE-CELLS IN CULTURE BY BETA-ADRENERGIC AGONISTS

The ability of beta-adrenergic agonists to stimulate ornithine decarbo xylase activity (ODC) in chick muscle cell culture prepared from 11-da y old embryos was evaluated. After 72 h of preincubation (myotube form ation) the medium was supplemented for 4 h with noradrenaline, ritodri ne, isoproterenol or clenbuterol, at concentrations of 10(-12), 10(-9) and 10(-6) mol/l. No significant response of ODC activity to noradren aline was observed. The highest concentration (10(-6) mol/l) of the be ta-adrenergic agonists ritodrine and isoproterenol elevated the activi ty of ODC. Clenbuterol was the most active beta-adrenergic agonist. Th e lowest concentration (10(-12) mol/l) had an apparent effect on ODC a ctivity in muscle cell culture, and the substitution of media at level s of 10(-9) and 10(-6) mol/l had a similar effect in comparison to con trols. The potency of beta-adrenergic agonists in increasing ODC activ ity was on the following order: noradrenaline, ritodrine, isoprotereno l, clenbuterol. Results indicate that beta-adrenergic agonists may dir ectly stimulate ODC activity followed by physiological processes in th e muscle cells ill the early stage of chick embryonic development.