EFFECT OF SOMATOTROPIN ON MYOSIN EXPRESSION IN PIGS

Daily administration of recombinant porcine somatotropin (rpST) has ma rked effects on growth performance of swine. Protein accretion rates a re dramatically increased with rpST treatment. However, the effect of rpST on specific muscle proteins has not been addressed. The purpose o f this study was to examine the effects of rpST on 1) the distribution pattern of isomyosins, 2) the total myosin heavy chain protein levels , and 3) myosin heavy chain mRNA abundance present in swine skeletal m uscle. There were no differences in myosin isoform composition in the longissimus muscle resulting from porcine somatotropin treatment. Ther e were also no differences in the myosin heavy chain protein concentra tion within the longissimus muscles. In accordance with the protein le vels, myosin heavy chain mRNA expression was not altered with rpST tre atment. This study shows that although the pig responds to rpST with i ncreased protein accretion rates, the proportion of myosin per milligr am of total protein remains constant. Myosin was not altered by type, concentration, or expression level. By combining these tools we are no w able to examine a myosin on both a protein and message level through out growth.