DISTRIBUTION OF HEME OXYGENASE AND EFFECTS OF EXOGENOUS CARBON-MONOXIDE IN CANINE JEJUNUM

Carbon monoxide (CO) has been postulated to be a messenger in the gast rointestinal tract. The aims of this study were to determine the distr ibution of heme oxygenase (HO), the source for endogenous CO in the ca nine jejunum, and to determine the effects of CO on jejunal circular s mooth muscle cells. HO-2 isoform was present in a population of myente ric and submucosal neuronal cell bodies, in nerve fibers innervating t he muscle layers, and in smooth muscle cells. HO-1 isozyme was not det ected in the canine jejunum. Exogenous CO increased whole cell current by 285 +/- 86%, hyperpolarized the membrane potential by 8.5 +/- 2.9 mV, and increased guanosine 3',5'-cyclic monophosphate (cGMP) levels i n smooth muscle cells. 8-Bromo-cGMP also increased the whole cell curr ent. The data suggest that endogenous activity of HO-2 may be a source of CO in the canine jejunum and that exogenously applied CO can modul ate intestinal smooth muscle electrical activity. It is therefore reas onable to suggest a role for endogenously produced CO as a messenger i d the canine jejunum.