SPECIES-INDEPENDENT EXPRESSION OF NITRIC-OXIDE SYNTHASE IN THE SARCOLEMMA REGION OF VISCERAL AND SOMATIC STRIATED-MUSCLE FIBERS

The expression and distribution of nitric oxide synthase (NOS) was stu died by use of the newly designed specific histochemical NADPH diaphor ase staining method and the indirect immunofluorescence technique empl oying an antiserum to brain NOS in visceral and somatic striated muscl es of several mammalian species. Histochemical activity and immunoreac tivity were located in the sarcolemma region of type I and II fibers o f all muscles investigated, Visceral muscles were more strongly staine d than somatic muscles. Furthermore, type II fibers, identified by sta ining of myosin adenosine triphosphatase activity after pre-incubation at alkaline pH, were more intensely labeled than type I fibers. In ad dition, NOS activity was detected in the area of the sarcolemma of int rafusal fibers. No obvious differences between species were observed. It was concluded that NOS of striated muscles probably makes up the ri chest and most important nitric oxide source in mammals.