Tetraphenylborate stimulation of phospholipid labeling in goldfish brain.

The presence of tetraphenylborate (TPB, 10 -3 M to 10 -4 M) in goldfish brain articulate preparations during a 5-15 min incubation with Y-~~P-ATP or y3f; P ATP results in marked stimulation of labeling of phosphatidate and a decrease in labeling of phosphatidyl inositol phosphate. Incorporation into phosphatidyl inositol diphosphate, a minor labeled phospholipid, is also depressed by TPB. We suggest the TPB effect is mediated by stimulation of a phosphodiesterase releasing diglyceride from phospholipid, which then reacts with labeled ATP, catalyzed by diglyceride kinase. Sodium tetraphenylborate (TPB) forms insoluble salts with potassium, ammonium and choline ions 3. . Dilute solutions dissociate cells', swell mitochondria3 , uncouple oxidative phosphorylation 4 and inhibit lightinduced uptake of monovalent cations by chloroplasts5. We report here that this unusual agent profoundly alters phospholipid labeling in goldfish brain preparations. Methods. 'Goldfish brain homogenates (1:3, in 0.25 M sucrose) were used directly or as a source of microsomal fraction. Following removal of cellular debris at 1OOOxg for 10 min, mitochondria and other large particles were sedimented by centrifugation at 20,OOOxg for 10 min, and the microsomal pellet was obtained by centrifugation of the supernatant fraction at 100,OOOxg for 60 min. Incubations were at 20' in 1.2 ml containing 33 mM glycylglycine