Changes in the transport of mitochondrial Ca2+ during the culture growth cycle of Tetrahymena pyriformis.
The properties of the Ca2+ transport system of mitochondria, isolated in various phases of growth of static cultures of Tetrahymena pyriformis, were studied. A large increase in the endogenous energy-dependent Ca2+ content of mitochondria was observed as cultures of T. pyriformis passed through the exponential and stationary phases of growth (approx. 0.25 and 50 nmol Ca2+ per mg mitochondrial protein, respectively). Simultaneously, the mitochondria dramatically lost their ability to withstand large concentrations of Ca2+ and ADP. However, in the latter case they were able to phosphorylate a large amount of ADP if the strong Ca2+ chelator, ethylene glycol bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, was initially present in the incubation medium. Furthermore, all the changes observed in mitochondria from the stationary phase cells were completely reversed when cell proliferation was re-activated after the lag phase, either by reseeding the stationery cells in fresh growth medium or by oxygenation of the old medium. In aerobic conditions even a small addition of Ca2+ was able to induce rapid release of Ca2+ from mitochondria isolated during the stationary phase of growth. It is suggested that the redistribution of Ca2+ between the mitochondria and the cytoplasm at the onset of the lag phase may serve as the main trigger for the subsequent biochemical and morphological changes observed in T. pyriformis.
D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D008928:Mitochondria / Q000378:metabolism*; D010766:Phosphorylation; D013769:Tetrahymena pyriformis / Q000254:growth & development*
D002118:Calcium