THE EFFECT OF pH ON THE OXYGEN CONSUMPTION OF TISSUES.*

In simple chemical oxidation such as the oxidation of pyrogallol or of a ferrous salt, the hydrogen ion concentration plays an important role. In general, as in the case of pyrogallol, a slight acidity depresses oxidation, and increasing alkalinity, even to a marked degree, greatly increases the rate of oxidation. It has been assumed that in general this applied also to biological oxidation, but there have been few observations upon this subject. Recently Btichner and Graft (1) concluded from their experiments, using the method of Warburg, that changes of pII had little effect on t,he oxygen consumpt,ion of finely cut tissue suspensions. These authors state that the oxygen consumption between pH 5 and 9 is practically constant and is diminished only at either extreme, gradually at. first and then more markedly. These findings are rather surprising in view of our general knowledge of oxidation, lwt especially in the light, of other investigations. The work of Warburg (2) and McClendon and Mitchell (3) showed t.hat in general an increase in hydroxyl ion concentrat,ion increased the oxygen consumption of sea urchin eggs and nucleated erythrocytes. Bunzell (4) showed that the oxidase activity of plant material is markedly sensitive to changes in pII, and that from a complete inhibition at approximately pH 3, the activity increased up to pH 7. Unfortunately the alkaline side was not investigated.