Nicotine-evoked exocytosis from bovine chromaffin cells is independent of phospholipase D activation

Phospholipase D (PLD) has been proposed to have a pivotal role in exocytosi s from various cells. We studied in bovine chromaffin cells, whether nicoti ne activates PLD and whether inhibition of the PLD-dependent phosphatidate production by primary alcohols inhibits exocytosis. Nicotine (10 mu M) and K+ (56 mM) failed to increase PLD transphosphatidylation activity while pho rbol-12-myristate-13-acetate (1 mu M) had a prominent effect. Ethanol (260 mM) reduced the noradrenaline release evoked by nicotine and K+, and 160 mM butyl alcohols (n-, sec-, and tert-butanol) nearly totally abolished it. T he alcohols raised the intracellular Ca2+ concentration both in the presenc e and absence of extracellular Ca2+. The butyl alcohols abolished and ethan ol reduced the nicotine-evoked calcium transients. As only primary alcohols effectively inhibit the phosphatidate formation, other mechanisms than PLD modulation mediate the effects of butyl alcohols. Our results suggest no c ritical role for PLD in exocytosis from intact chromaffin cells nor in nico tine signalling. The alcohol effects on nicotinic responses may rather depe nd on altered calcium signalling and membrane properties.