Anabolic actions of a mixed beta-adrenergic agonist on nitrogen retention and protein turnover.

Subcutaneous administration of a mixed beta-agonist induced increases in muscle (+13%) and heart (+17%) weights, which were accompanied by a reduction in back (-13%) and perirenal (-27%) fat stores in young male rats, while no changes in liver were observed. The values of nitrogen retention (mg/day) were significantly higher in the beta-agonist treated animals (+16%) as well as those of muscle DNA content (+8%). On the other hand, no statistically significant changes in muscle protein synthetic activity (g protein synthetized/g RNA) were detected (control: 13.4 vs treated: 14.6), while muscle proteolytic activity was decreased (-9%) in those rats administered with the repartitioning agent. In this context, it is suggested that the anabolic effect of metaproterenol should be attributed to a reduction in muscle protein degradation rather than to changes in protein synthesis.