The effect of potassium on the glucolysis of brain tissue with reference to the Pasteur effect

Abstract

VARIous explanations have hitherto been put forward as to the mechanism of the Pasteur effect. Meyerhof et al. [1925] and others have suggested that the lactic acid formed in anaerobiosis is also formed under aerobic conditions, but here removed by oxidation and perhaps resynthesis. Another explanation has been given by Lipmann [1933], who considers that oxygen interferes with the activity of the fermentative or glucolytic enzyme and thus spares glucolysis. It seemed also possible that one of the reactants in the lactic acid-forming reaction (as demonstrated by the work of Embden et al. [1933] and Meyerhof and Kieseling [1933] in the case of muscle) might be removed by oxygen. Thus, assuming glucose to split into two molecules a and bwhich react together to give lactic acid, we have glucose = a + b =2 lactic acid. If either a or b is removed by oxygen, lactic acid formation is lessened, and furthermore one atom of oxygen could prevent the formation of 2 molecules of lactic acid. That is, one molecule of oxygen absorbed prevents 4 molecules of lactic acidfrom accumulating, and in this waya maximum Meyerhof quotient of 4 could be explained. In the original project, it was decided in the first place to investigate the effect of adding o-glycerophosphate and pyruvate (which was already known [Bumm et al., 1933; Mendel et al., 1931] to increase anaerobic glucolysis) to tissues in which oxygen was exercising its sparing action on glucolysis. If either of these substances occurred in the normal glucolysis and was removed by oxygen, addition of this substance during aerobiosis might restore and increase the aerobic glucolytic rate. It was necessary to use for this purpose a tissue with low aerobic glucolysis, and for this purpose brain slices were selected for a start, although it is not believed [Ashford and Hjolmes, 1929; Ashford, 1933; 1934] that the Embden-Meyerhof scheme for glucolysis obtains in brain tissue. The work reported here is the outcome of these experiments. METHODS. The tissue employed was the cortex of rabbit's brain. Slices of this were cut immediately after the rabbit was killed. These slices were immersed in 10 ml. of liquid which contained Ringer in normal concentration and 0-025M sodium bicarbonate. In this solution glucose was present in a concentration of 0-2 %, also any substance whose effect on glucolysis was to be determined. This volume of fluid containing the slices was contained in flasks provided with glass stoppers (as described in a previous paper [Ashford, 1934]). Oxygen or nitrogen containing 5 % CO2 was bubbled through the liquid in which the slices were immersed for 1 Beit Memorial Research Fellow.