ROLE OF CATALASE IN RAT GASTRIC-MUCOSAL ETHANOL-METABOLISM IN-VITRO

To evaluate the possible role of catalase in gastric ethanol metabolis m in rats, we studied acetaldehyde formation from ethanol by gastric m ucosal homogenate under various in vitro conditions. Homogenized rat g astric mucosa produced significant amounts of acetaldehyde in a time a nd ethanol concentration-dependent manner, even in the absence of adde d NAD. Both acetaldehyde formation and catalase activity peaked around the physiological pH, whereas alcohol dehydrogenase (ADH) activity wa s in that pH range low and reached peak values only at a higher pH of 9 to 10. Catalase inhibitors sodium azide (SA) and 3-amino-1,2,4-triaz ole (3-AT) had little effect on ADH activity but markedly decreased, c atalase activity and acetaldehyde formation (1 mM of SA to 56 +/- 13% of control, 5 mM of 3-AT to 67 +/- 3% of control; mean +/- SE). 4-Meth ylpyrazole decreased ADH activity significantly, but did not affect ac etaldehyde formation. Heating of the homogenate at 60 degrees C for 5 min decreased ADH activity only slightly, but totally abolished catala se activity and reduced acetaldehyde formation to 39 +/- 3% of control . Addition of a H2O2 generating system [beta-D(+)-glucose + glucose ox idase] increased acetaldehyde formation in a concentration-dependent m anner up to 8-fold of the control value. Our results strongly suggest that, in addition to ADH, catalase may play a significant role in gast ric ethanol metabolism in rats.