Effect of graded mechanical ischemia on oxygen tension and electrical potential in the canine gastric mucosa. A new experimental model.

Oxygen tension and potential difference were measured in the gastric mucosa of anesthetized dogs with an ultramicroelectrode technqiue while total blood flow and arteriovenous oxygen content difference were measured. In the control period, measurements were: gastric blood flow, 102.4 +/- 3.0 ml per min per 100 g of tissue; calculated oxygen consumption, 2.4 +/- 0.1 ml per min per 100 g of tissue; intracellular oxygen tension, 15.0 +/- 0.6 mm Hg; and intracellular potential difference, -50.8 +/- 1.5 mv. When gastric blood flow was reduced 50% by tourniquet ischemia, oxygen tension decreased 20% (P less than 0.05) but electrical potential and oxygen consumption did not change. When blood flow was reduced 75%, oxygen tension and potential difference decreased significantly, 60% and 35%, respectively, but oxygen consumption was unchanged. Zero blood flow reduced oxygen tension, electrical potential, and total oxygen consumption to zero; release of the arterial tourniquet allowed them to return to control levels. The critical oxygen tension at which the electromotive force generated by the gastric mucosal cells was reduced averaged 9 mm Hg. This suggests that safety factors exist in the gastric circulation which permit a 60% reduction in total gastric blood flow to occur before an insufficiency of intracellular oxygen begins to limit cellular metabolism within the mucosa.