Expression of endothelial nitric oxide synthase in human eccrine clear cells.

Nitric oxide is generated from L-arginine by nitric oxide synthase (NOS), which has at least three isoforms; endothelial-type NOS (eNOS) and brain-type NOS (bNOS) are constitutive enzymes, and inducible-type NOS (iNOS) is expressed after stimulation. Studies by the avidin-biotin immunocomplex method, revealed eNOS immunoreactivity exclusively in the human eccrine clear cells. No eNOS immunoreactivity was observed in the eccrine dark cells or myoepithelial cells. No staining of iNOS or bNOS was observed in the eccrine gland. These findings indicate that NO plays a physiological part in the production and/or excretion of sweat in the human skin eccrine gland.