Studies on the mechanism of the toxic action of sodium nitrite on intestinal absorption in rats.

The biochemical parameters Na+/K(+)-ATPase, alkaline phosphatase, oxygen consumption, and lactic acid level were evaluated in the small intestine mucosa of male Wistar rats during in situ perfusion of the rat with sodium nitrite. Sodium nitrite was poorly absorbed (10% of the administered dose), but it inhibited the activity of Na+/K(+)-ATPase and alkaline phosphatase. It had no effect on the lactic acid level, pointing to normal oxygen in the intestine, evidently reducing the utilization of oxygen by this tissue. Using metabolism inhibitors added to the perfusion fluid in the concentrations: ouabaine 0.1 mM, NaN3 (sodium azide) 1 mM, L-phenylalanine 50 mM and during functional ischaemia of the intestine produced by occlusion of the superior mesenteric artery for the time of the perfusion, it was possible to find the site of action and the direction of the toxic influence of sodium nitrite.