Nicotine-like effects of cotinine on protein kinase C activity and noradrenaline release in bovine adrenal chromaffin cells

1 We studied the effect of cotinine, a slowly eliminated metabolite of nicotine, on protein kinase C (PKC) distribution and noradrenaline release in primary cultured bovine adrenal chromaffin cells. Changes in PKC activity were detected by [H-3]-phorbol-12,13-dibutyrate binding, histone phosphorylation assay and by Western blot. 2 Cotinine (10-32 mM) increased phorbol binding to chromaffin cells in response to 10 min but not to 24 h exposure. The increased binding was reversed by a nicotinic antagonist hexamethonium (10 mu M). 3 Cotinine (10 mM, 30 min) also increased membrane-associated PKC activity and membrane-associated PKC alpha and epsilon immunoreactivity. 4 Cotinine (0.1-32 mM for 10 s to 20 min) dose- and time-dependently increased the release of preloaded [H-3]-noradrenaline from the cultured cells. The release increased with increasing duration of the contact period. In treatments lasting 1 min or longer, a peak effect was followed by a reduced response at higher concentrations. 5 We confirm the earlier findings that cotinine is biologically active, and conclude that its effects are at least partly mediated via nicotinic cholinergic receptors and through PKC.