CALCITONIN-GENE-RELATED PEPTIDE STIMULATES DIFFERENTIATION OF NEONATAL RAT MYOGENIC CULTURES

The effect of the nerve derived peptide, calcitonin gene related pepti de (CGRP) on myoblast fusion/differentiation was studied in rat myogen ic cell cultures, using creatine kinase activity as an index of fusion . Addition of CGRP at 10(-7) M to myoblast cultures resulted in an enh ancement of creatine kinase activity after 11 days of treatment. This response was not accompanied by increased protein content of cultures implying an effect primarily on fusion rather than on myotube growth/s ize. Neither was it a direct effect on enzyme activity alone since no increase in creatine kinase activity occurred when CGRP was added to m ature myotube cultures. These data suggest a role for CGRP in the myob last fusion process itself and raise questions as to its importance in the growth and development of muscle in vivo.