[Increase of perfusion pressure at constant perfusion rate caused by low pH values]

One hind leg each of 20 rats was perfused by a buffer-electrolyte mixture at a rate of 1.2 ml/min. When the pH of the solution was lowered from 7.4 to 7.0 and, thereafter, to around 6.0, the mean perfusion pressure increased by 1.6 to 3.4 and 2.5 to 12.4 kPa, respectively. The higher values were obtained when the perfusate contained 2.5% dextran (m.w. 40,000). Swelling of endothelial cells and vasoconstriction are discussed as possible effector mechanisms.