Phospholipid metabolism of 3T3 mouse fibroblasts after serum stimulation and through the G1 and S cell cycle phases : incorporation and disappearance of 32P.

Phospholipid metabolism of 3T3 mouse fibroblasts has been studied after serum stimulation of arrested cells. The study of [32Pi] incorporation shows : a) in the case of PE and PC an early peak of incorporation in the G1 phase of the cell cycle, 6 hours after serum addition; b) in the case of PI an intense initial increasing of the incorporation which continues up to a S phase peak. The study of the disappearance of [32P] Phosphate from the different phospholipids points out: a) at the beginning of serum stimulation, an intense breakdown of PI, that continues through the G1 and S phases. Except at the onset, the breakdown of PI, is at any time exactly compensated for by synthesis : the two phenomena are closely linked; b) a synthesis of PE, from PC probably, at the G1 phase, 4 hours after the serum addition and the beginning of the chase experiment.