DISTRIBUTION OF CONSTITUTIVE NITRIC-OXIDE SYNTHASE IMMUNOREACTIVITY AND NADPH-DIAPHORASE ACTIVITY IN MURINE TELOGEN AND ANAGEN SKIN

The freely diffusible radical nitric oxide is generated by nitric oxid e synthase, and is a pleiotropic, bioregulatory molecule that regulate s, e.g., the vascular tone, functions as a major neurotransmitter, and is involved in macrophage-mediated cytotoxicity and platelet aggregat ion. Constitutive nitric oxide synthase exhibits NADPH-diaphorase acti vity that can be demonstrated histochemically. To study whether this e nzyme is present in mammalian skin during distinct phases of the murin e hair cycle, we have examined cryosections of C 57 BL-6 mouse skin in telogen and depilation-induced anagen VI. Histochemical analysis of N ADPH-diaphorase activity was complemented by immunohistology, using tw o specific rabbit antisera against constitutive neuronal nitric oxide synthase. Epidermis and the outer root sheath showed both immunoreacti vity for the enzyme and NADPH-diaphorase activity, whereas dermal papi lla and sebaceous glands displayed only strong NADPH-diaphorase activi ty, suggesting that this enzyme histochemical test measures additional enzymes besides nitric oxide synthase. Intrinsic nitric oxide synthas e immunoreactivity was also detected by immunoblot in mouse skin homog enates, staining proteins of an apparent 160-kDa molecular weight. Com pared to telogen skin, these immunoreactive proteins were quantitative ly increased in anagen VI skin. Thus, our study suggests that defined epithelial compartments of normal murine skin are capable of synthesiz ing nitric oxide and that the molecule may be involved in skin physiol ogy, growth, and remodeling.