Labelling of phospholipid phosphorus in rat-brain mitochondria

Abstract

Phospholipid was labeled from inorganic P32 in mitochondria separated from dispersions of rat brain prepared in isotonic sucrose. Labeling was best observed under optimum conditions for oxidative phos-phorylation. Addition of adenine nucleotide, Mg2+ ions, diphosphopyridine nucleotide and cytochrome c was necessary for optimum P32 incorporation. Labeling was supported by addition of glutamate and certain tricarboxylic acid cycle intermediates, but not by addition of citrate. Labeling of lipid P and adenosine triphosphate (ATP) was inhibited by addition of 2,4-dinitrophenol or cyanide, was insensitive to iodoacetate and was stimulated by addition of fluoride. Addition of dini-trophenol and fluoride also caused changes in the steady-state concentrations of ATP, adenosine diphosphate and adenosine monophosphate. There are probably 2 systems capable of supporting P32 labeling in rat-brain dispersions: (1) an anaerobic glycolytlc system best demonstrated in water dispersions, and (2) an aerobic system best demonstrated in mitochondria prepared from isotonic sucrose dispersions.