Tissue Respiration and Transamination in Cold Stress

Abstract

IN the phylogenetic evolution of thermoregulation, under cold stress, liver and kidney tissues of poikilothermal toads show a marked increase in succinate and ascorbate oxidation to 105–150 per cent of that at 30° C. ; in stenothermal birds, there is an increase of only 22–35 per cent, while in the homoiothermal rat there is a depression of 21–27 per cent. This indicates that in the rat the depression of respiration is greater in flavoprotein or preflavoprotein systems than in the cytochromes, while in the toad and bird the augmentation of respiration by cytochrome system is 1.2–1.3 times greater than in the flavoprotein or preflavoprotein systems¹. An attempt has been made in the present work to locate the nature of the evolution of oxidative enzymes in the preflavoprotein systems and also to indicate the nature of changes in oxygen consumption with amino-acid substrates and transamination in these systems.