ACID FORMATION IN FROZEN AND THAWED ARBACIA PUNCTULATA EGGS AND ITS POSSIBLE BEARING ON THE PROBLEM OF ACTIVATION

¹ From the Institute of Experimental Zoölogy, Stockholm, Sweden, and the Marine Biological Laboratory, Woods Hole

In previous work it has been found that the activation process is accompanied by an acid formation which has been demonstrated by manometric methods. A comparatively strong acid formation takes place also when the eggs are broken up by distilled water. It seems possible in view of certain observations reported above that the acid formation in both cases has the same chemical basis. The work reported has to be regarded as a first approach to a closer study of this question, which has a bearing on the understanding of the activation process.

The eggs have been broken up in the experiments reported by freezing and thawing. During the thawing a considerable acid formation takes place by far exceeding that observed in the activation process. The acid formation was estimated by manometric determinations of the decrease of combined carbonic acid. In a number of experiments the solid particles of the thawed suspensions were centrifuged down. The fluid part has a lower content of combined carbonic acid than the suspension as a whole. Possibly the proteins of the solid particles combine with carbonic acid under the given conditions. The fluid part of the egg suspensions exercises a visible effect on the jelly surrounding the eggs.

Monoiodoacetate 0.03 m, fluoride 0.06 m, and copper 0.0004 per cent have no inhibiting effect on the acid formation. Addition of hexosemonophosphate does not seem to enhance the acid formation. Iodoacetate in presence of hexosemonophosphate does not inhibit the acid formation. Hence it seems extremely unlikely that the acid formation has anything to do with lactic acid formation. Phosphorylation of hexoses or dephosphorylation of phosphoglyceric acid seem to be excluded by the iodoacetate, and the fluoride experiments. Proteolysis under the action of cathepsin is also excluded by the iodoacetate experiments. An oxidation-reduction system like pyocyanine has no influence on the amount of acid formed.

Suspensions of thawed eggs + hexosemonophosphate + pyocyanine form a system with a fairly high oxygen uptake. This is decreased by 30 per cent on addition of 0.03 m iodoacetate or 0.06 m fluoride. This proves that the two substances in question interfere with the carbohydrate metabolism in this system.