Qualitative difference in mitochondria of endothermic and ectothermic animals

Abstract

A significantly higher rate of respiration in the absence of added ADP has been revealed in mitochondria of endotherms as compared with that of the ectotherms with similar rates of respiration during phosphorylation. A high rate of ADP-independent (non-coupled with ATP synthesis) respiration is observed during oxidation of succinate, NADH and ascorbate + cytochrome c, but not with NAD-dependent substrates. It increases in the presence of cytochrome c during oxidation of succinate and NADH and is also revealed during oxidation of NAD-dependent substrates in the presence of NAD+ and cytochrome c. ADP-independent respiration is not affected by oligomycin, however, it is essentially inhibited in the presence of GDP. It is suggested that the significant difference in the value of ADP-independent respiration of endo- and ectotherms is due to the existence in endotherms of a non-coupled population of mitochondria which generates heat without preliminary synthesis of ATP.