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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 [3H]-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 μm).

3 Cotinine (10 mm, 30 min) also increased membrane-associated PKC activity and membrane-associated PKC α and ε immunoreactivity.

4 Cotinine (0.1–32 mm for 10 s to 20 min) dose- and time-dependently increased the release of preloaded [3H]-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.