CONCLUSIONS

1. Bovine adrenal chromaffin cells possess PLD protein and PLD1-like activity that can be activated by G-protein coupled receptor activators angiotensin II and bradykinin, and by phorbol ester stimulation of PKC.
2. PLD activation is not necessary for chromaffin cell exocytosis. Neither does PLD participate in nicotine signalling nor in sustained chromaffin cell responses to angiotensin II or bradykinin.
3. Cotinine inhibits nicotinic responses, such as elevation of [Ca⁺⁺]_i, increase in PKC activity and noradrenaline exocytosis, in bovine adrenal chromaffin cells.
4. Cotinine efficiently stimulates bovine adrenal chromaffin cells, but high concentrations are required. The cotinine-evoked responses include elevation of [Ca⁺⁺]_i, increase in PKC activity, and noradrenaline exocytosis.
5. Cotinine binds to nicotinic binding sites at acetylcholine receptors. The nicotinic acetylcholine receptor agonism initiates the chromaffin cell responses to cotinine.
6. Cotinine affinity for nicotinic acetylcholine receptors is low, and the cotinine concentrations achieved in nicotine consumption are likely to affect the receptor activity states.