STIMULATION OF ACTIN AND MYOSIN SYNTHESIS IN RAT GASTROCNEMIUS-MUSCLE BY CLENBUTEROL - EVIDENCE FOR TRANSLATIONAL CONTROL

1. A transient rise in fractional rates of protein and actomyosin synthesis was observed in gastrocneumius muscles of rats fed clenbuterol for 1-2 days but the muscle RNA:protein ratio was unchanged, therefore protein synthesis per unit RNA (k(RNA)) also increased. 2. Myosin heavy and light chains and actin showed increased incorporation of [H-3]phenylalanine at 2 days; these changes were proportional to increases in total protein synthesis. 3. The ratios actin mRNA : 18S RNA and fast myosin heavy chain mRNA : 18S RNA were unaffected by clenbuterol. 4. The data suggest that the clenbuterol-induced increase in muscle protein synthesis involves both translational control and increased tissue RNA.