[Regulation of the number and function of mitochondria during artificial increase of their mass in fish embryos].

The mechanisms of mitochondrial mass reduction were investigated by microinjection of mitochondria in developing loach embryos. This reduction can be due to the degradation of the injected mitochondria or to the triggering of regulatory mechanisms. In the latter case the decrease of mitochondrial excess should be caused by exogenous and endogenous mitochondria of the embryos. When the protein-labelled mitochondria were injected into unlabelled eggs or the unlabelled mitochondria were injected into the eggs containing labelled mitochondria, the label content in the mitochondrial protein was decreased 2-fold within 12 hours and then remained unchanged at later stages of embryogenesis. After injection of 3H-labelled mitochondria into the 14C-labelled eggs the 3H/14C ratio in the mitochondrial protein during embryogenesis remained unchanged. These data suggest that the restoration of the normal amount of the mitochondrial mass is caused by the triggering of regulatory mechanisms. Oxygen uptake in the embryos with the artificially increased amount of mitochondria is maintained at a control level or even below control, i. e. undergoes regulation. In the homogenates of these embryos the regulatory control is absent and oxygen uptake is proportional to the amount of mitochondria.