CHARACTERIZATION AND ONTOGENY OF NITRIC-OXIDE SYNTHASE ACTIVITY IN PIG ENTEROCYTES

Nitric oxide has been implicated as a local modulator of several gastr ointestinal functions. In this study, we have measured nitric oxide sy nthase activity in homogenates of enterocytes isolated from post-weane d pigs. The enzyme required the presence of NADPH and 6-(R,S)-5,6,7,8- tetrahydro-L-biopterin. Conversely exogenous FAD and FMN did not appea r to be necessary for enzyme activity. The enzyme activity was not aff ected by added Ca2+ or EGTA and was inhibited by the arginine analogs N(G)-monomethyl-L-arginine and N(omega)-nitro-L-arginine. NO synthase activity was not detectable in enterocytes isolated at birth and incre ased slightly in suckling animals. NO synthase activity was found to b e present mostly in the cytosolic fraction isolated from post-weaned p igs enterocytes.