Maturation of rabbit reticulocytes: susceptibility of mitochondria to ATP-dependent proteolysis is determined by the maturational state of reticulocyte.

A simple procedure is described to separate reticulocytes of different maturity in high yield. It is shown that exhaustion of supply of mitochondria susceptible to degradation by the lipoxygenase-ATP-dependent proteolysis system limits the extent of breakdown of mitochondria during in vitro maturation. The susceptibility of mitochondria depends on the maturity of the reticulocytes. Incubation in the presence of calcium ions and calcium ionophore leads to full susceptibility of mitochondria in immature reticulocytes but has no effect on those in mature reticulocytes which are already fully susceptible to degradation. Conditions which lead to rapid degradation of mitochondria do not affect the behaviour of the reticulocyte count. There appears to be no obligatory connection between the breakdown of mitochondria and of ribosomes.