Mitochondrial biochemical events in a synchronized mammalian cell population.

L5178Y cells were synchronized and protein, glycoprotein, DNA and RNA synthesis in the mitochondria were measured. Mitochondrial synthesis in viva in the intact L5178Y cell, and in vitro in isolated mitochondria from synchronous L5178Y cells was measured. In viuo mitochondrial protein synthesis occurred primarily in G1 and Gz; in vitro the synthesis by the isolated mitochondria of protein occurred only in G1. Mitochondrial DNA synthesis in uiuo occurred in S and Gz; in vifro DNA synthesis was greatest in the GZ period. RNA synthesis in vivo occurred with three peaks of activity, two in S and one in Gz; in vitro only the G2 synthesis was prominent. Glycoprotein synthesis in the L5178Y cell mitochondria in vivo occurred in Gi, S, GP; in vitro the major synthesis was confined to G1. Two mitochondrial enzymes, succinic dehydrogenase and monoamine oxidase were found to be S peak enzymes in the synchronized L5178Y cells.