Effect of Malonate and Iodoacetate on Respiration of Brains of Rats of Various Ages

Abstract

Discussion and Conclusions

Malonate has been assumed to be a specific inhibitor of succino-dehydrogenase. 5 If this assumption is correct, the above results indicate that the brain of the newborn does not depend on the oxidation of succinate to the same extent as does the adult's brain. However, the specificity of the action of malonate has been questioned, and evidence indicates that its effects are more complex and cannot be due primarily to an inhibition of that one enzyme. 6 , 7 , 8 Irrespective of which enzyme systems are inhibited by malonate, it is clear that, compared with the infant brain, the adult's is more sensitive to this substance. It is interesting to note that the increase in the respiration of the malonate poisoned tissue occurs at about the same time that myelinization is known to begin in the rat. 9 , 10 Apparently, this increase is due to a system not very sensitive to malonate.

The results with iodoacetate seem to imply that the brain of the newborn depends, for its aerobic metabolism, on some of the degradation products of glycolysis to a relatively greater degree than does the brain of the adult.