Sodium fluoride unmasks the accumulation of lysophosphatidylcholine in intact pancreatic islet cells.

When intact but dispersed neonatal islet cells, prelabelled with [14C-Me]choline, were stimulated with a calcium ionophore, ionomycin alone elicited only small rises in lysophosphatidylcholine; in contrast, pretreatment for 20 min with sodium fluoride (20mM) unmasked a consistent accumulation of lysophospholipid (to 155% of control at 1 min, 162% at 5 min and 212% at 10 min). Fluoride was shown to inhibit (by 40-50%) the reacylation of exogenous acyl- or alkyl-linked lysophosphatidylcholines by a delayed and indirect effect, whereas, in contrast, 12-O-tetradecanoylphorbol-13-acetate or dioctanoylglycerol actually augmented acylation. Thus, increased production of lysophosphatidylcholine in intact islets is obscured by rapid removal mechanisms, one of which might involve protein kinase C (or diglycerides directly). The use of sodium fluoride partially obviates this clearance, but this finding may necessitate a re-interpretation of claims that G protein agonists such as fluoride directly activate phospholipase A2 in some cells.