Rapidly-labelled, acidic phospholipids of the goldfish brain

Homogenates and particulate fractions of goldfish brain incorporated radioactivity from γ-[³²P]ATP selectively into acidic phospholipids during brief periods of incubation. Phosphatidate and lysophosphatidate became strongly labelled and activity was also found in phosphatidyl inositol phosphate and in phosphatidyl inositol diphosphate. When tetraphenylborate (a K⁺-complexing agent) was added, a selective stimulation of incorporation of ³²P into phosphatidate occurred. The addition of perchlorate (also known to bind K⁺) did not produce a similar stimulation, nor did the addition of K⁺ block the stimulation by tetraphenylborate. The stimulation of the labelling of phospholipids by tetraphenylborate appeared to be the result of multiple actions. Besides the evidence that it acted by stimulating the phosphoinositide phosphodiesterase of brain, data were obtained suggesting that it stimulated diglyceride kinase and blocked endogenous destruction of ATP as well. The stimulation by tetraphenylborate was blocked by addition of atropine but not of arecoline.