[Effects of calcitonin gene-related peptide on muscle cell differentiation and development]

We studied the factors which facilitate muscle cell differentiation and development to produce preventive and therapeutic treatment for muscle atrophies. Calcitonin gene-related peptide (CGRP) is present in the nervous system and neuromuscular junction, and acts as either a neurotransmitter or a neuromodulator. In this study, we report the effects of CGRP on the differentiation and development of rat skeletal myoblasts. Rat skeletal myoblasts (L6 cell) were cultured in Dulbecco's modified Eagle's medium containing 2% horse serum and 6 micrograms/ml insulin (control group). CGRP was then added at concentrations of 1, 10, and 100 nM (CGRP groups). Changes in cell morphology, myoglobin (Mb) content, creatine kinase (CK) activity, DNA content, and calcium concentration in the cultured cells were examined on days 3, 6, 8, and 10. In all of the groups, the number of cultured cells increased until myotubes appeared on day 6. The number of myotubes then rapidly increased until day 10. Additional cell culture became impossible because the cells were detached from the culture dish. The short axis length of the cultured cells reached a maximum of 59.4 +/- 5.2 microns on day 8 in the CGRP (10 nM) group. This value was significantly greater than that in the control group (43.7 +/- 3.9 microns). The ratio of Mb content/DNA content in the cultured cells increased in all of the groups and reached a maximum of 13.6 +/- 0.4 x 10(-2) ng.Mb/microgram.DNA in the CGRP (10 nM) group on day 10. This value was approximately 3 times higher than that in the control group (4.7 +/- 0.3 x 10(-2) ng.Mb/microgram.DNA).(ABSTRACT TRUNCATED AT 250 WORDS)