Phospholipid synthesis and exchange between rat liver microsomes and mitochondria in the presence of benzo(a)pyrene.

Benzo(a)pyrene injection increased the phospholipid content in membranes of rat liver mitochondria and microsomes. There was a large relative increase of phosphatidylcholine, especially in microsomes, as compared with normal liver. The quantity of phosphatidylethanolamine seemed not be affected and the other phospholipid classes decreased. In vivo [U-14C]glycerol incorporation into phospholipids was greater after benzo(a)pyrene injection, especially into phosphatidylcholine. Liver microsomes derived from rats injected with [U-14C]glycerol or from liver slices incubated with the same precursor were incubated with unlabeled mitochondria in the presence of 105,000 g supernatant fraction; labeled microsomal phospholipids exchanged to a greater extent in the presence of benzo(a)pyrene, suggesting either a stimulation of activity of the exchange proteins, or a relative membrane disorganization facilitating the phospholipid transfer.