Topographic and intracellular distribution of monoamine and diamine oxydases in rat stomach.

Up to now, the activity of D.A.O. and M.A.O. in the gastric mucosa of rat stomach has not been yet detected. Employing a radioisotopic method, modified by us, it was possible to detect the activity of both enzymes in sufficient amount to study their topographic and intracellular localization. Topographically, the antral region showed the highest activity for the two enzymes, being the D.A.O. 20 times stronger than the M.A.O. The intracellular localization of M.A.O. seems to be in the lysosomes but the D.A.O. looks like to be homogeneously distributed, except in the mitochondrial fraction. The simple demonstration of gastric intracellular distribution of these enzymes in the rat stomach should stimulate further investigations to elucidate the metabolism of histamine and its enzymatic regulations.