Labelling of phospholipid phosphorus in rat-brain dispersions

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Abstract
Dispersions of rat brain, prepared in water and suitably "reinforced", incorporated inorganic P32 into lipid P. Omission of cytochrome c or fumarate from the medium, or replacement of O2 with N2, did not inhibit the incorporation. Tricarboxylic acid cycle intermediates (citrate, malate or succinate) increased the respiration, but did not increase the aerobic P32 labeling of lipid P. Mg diphosphopyridine nucleotide, adenosine 5-phosphate (AMP) or adenosine triphosphate (ATP), and substrate that can undergo glycolysis (glucose, mannose or hexose diphosphate (HDP), but not galactose) were necessary for the incorporation under both aerobic and anaerobic conditions. Under anaerobic conditions a source of "high-energy" P (ATP, HDP plus AMP, uridine triphosphate plus adenosine diphosphate (ADP), or guanosine triphosphate plus ADP) was essential for optimum glycolysis and labeling of lipid P. Under anaerobic conditions, glycolysis and incorporation of inorganic P32 into lipid P were best demonstrated in dispersions prepared in water. Dispersions prepared in iso-tonic media (KC1 or sucrose) were considerably less active. Under aerobic conditions the addition of 2,4-dinitrophenol (7.5 x 10-5 [image]) caused increases in O2 consumption and glycolysis, but a decrease in the labeling of phospholipid. Under anaerobic conditions there was little change in glycolysis and a much smaller decrease in phospholipid labeling. The addition of fluoride (10-2 [image]) caused no significant change in O2 consumption and large inhibitions of both aerobic and anaerobic glycolysis. Labeling of phospholipid was increased under aerobic conditions, but decreased when O2 was excluded from the system. Addition of iodoacetate (10-5 [image]) caused small inhibitions of O2 consumption, aerobic glycolysis and aerobic labeling of phospholipid, but much greater decreases in glycolysis and phospholipid labeling under anaerobic conditions.