NITRIC-OXIDE AS A MESSENGER MOLECULE FOR MYOBLAST FUSION

Nitric oxide (NO) is a messenger molecule of vascular endothelial cell s, macrophages, and neurons. Here, we demonstrate that the activity of NO synthase increases transiently but dramatically in chick embryonic myoblasts that are competent for fusion. This activity requires Ca2+, calmodulin, and NADPH. In addition, the increase in NO synthase activ ity coincides with an increase in cellular cGMP level. Furthermore, NO generated by treatment with sodium nitroprusside induces precocious m yoblast fusion, while treatment with N-G-monomethyl-L-arginine, a comp etitive inhibitor of NO synthase, or methylene blue, an inhibitor of g uanylate cyclase, delays fusion. These results provide the first evide nce for a strong association of NO with myoblast fusion.