ORGANOPHOSPHATES INHIBIT CATECHOLAMINE SECRETION AND CALCIUM INFLUX IN BOVINE ADRENAL CHROMAFFIN CELLS

The lethality of organophosphorous compounds has been attributed to th eir inhibitory effect on acetylcholinesterase (AChE) in the nervous sy stem. However, subacute exposure of humans to organophosphates induces cognitive and emotional defects which might not solely be attributabl e to AChE inhibition. Therefore we investigated the toxic effects of m ethyl parathion and malathion on bovine adrenal chromaffin cells. Cate cholamine secretion and Ca-45(2+) uptake evoked by either a nicotinic agonist (DMPP) or high [K+] were inhibited by methyl parathion and mal athion. The [Ca2+](i) rise induced by DMPP was inhibited by both compo unds. We conclude that in addition to AChE, voltage-gated Ca2+ channel s and nicotinic receptors are possible sites of action of organophosph ates in mammalian systems.