EFFECTS OF THE ORGANOPHOSPHOROUS PESTICIDE, DIMETHOATE, ON CARDIAC AND ACETYLCHOLINESTERASE (ACHE) ACTIVITY IN THE SHORE CRAB CARCINUS-MAENAS

The potential use of biochemical and physiological responses as biomar kers of organophosphate exposure and/or effect were assessed in the sh ore crab (Carcinus maenas). Male crabs were assigned to one of four di methoate treatments (0, 0.5, 1.0 or 2.0 mg 1(-1)). Cardiac activity wa s measured non-invasively before and during dimethoate exposure using automated interpulse duration assessment. Heart rates decreased signif icantly in a concentration-dependent manner (p < 0.05). Serial measure ments of acetylcholinesterase activity in haemolymph samples taken fro m crabs before and after exposure indicated that 2 mg 1(-1) dimethoate also significantly reduced acetylcholinesterase activity (p < 0.05). The percentage inhibition in acetylcholinesterase activity was correla ted with the percentage reduction in heart rate following dimethoate e xposure (r=0.55, p < 0.01). This suggests that organophosphates may di rectly effect neuronal control of the heart, The experiments indicate that nondestructive, serial measurements of cardiac activity and acety lcholinesterase activity are valuable biomarkers of organophosphate ex posure and adverse effects. (C) 1997 Elsevier Science B.V.