OBJECTIVETo study the toxicity of methomyl to acetylcholinesterase (AChE) in different regions.

METHODSThe optimal temperature and time for measurement of AChE activity were determined in vitro. The dose- and time-response relationships of methomyl with AChE activity in human erythrocyte membrane, rat erythrocyte membrane, cortical synapses, cerebellar synapses, hippocampal synapses, and striatal synapses were evaluated. The half maximal inhibitory concentration (IC50) and bimolecular rate constant (K) of methomyl for AChE activity in different regions were calculated, and the type of inhibition of AChE activity by methomyl was determined.

RESULTSAChE achieved the maximum activity at 370 °C, and the optimal time to determine initial reaction velocity was 0-17 min. There were dose- and time-response relationships between methomyl and AChE activity in the erythrocyte membrane and various brain areas. The IC50 value of methomyl for AChE activity in human erythrocyte membrane was higher than that in rat erythrocyte membrane, while the Ki value of methomyl for AChE activity in rat erythrocyte membrane was higher than that in human erythrocyte membrane. Among synapses in various brain areas, the striatum had the highest IC50 value, followed by the cerebellum, cerebral cortex, and hippocampus, while the cerebral cortex had the highest Ki value, followed by the hippocampus, striatum, and cerebellum. Lineweaver-Burk diagram demonstrated that with increasing concentration of methomyl, the maximum reaction velocity (Vmax) of AChE decreased, and the Michaelis constant (Km) remained the same.

CONCLUSIONMethomyl is a reversible non-competitive inhibitor of AChE. AChE of rat erythrocyte membrane is more sensitive to methomyl than that of human erythrocyte membrane; the cerebral cortical synapses have the most sensitive AChE to methomyl among synapses in various brain areas.

Acetylcholinesterase ; metabolism ; Animals ; Cerebellum ; drug effects ; Cerebral Cortex ; drug effects ; Erythrocyte Membrane ; drug effects ; enzymology ; Hippocampus ; drug effects ; Humans ; Inhibitory Concentration 50 ; Methomyl ; toxicity ; Rats ; Synapses ; drug effects ; Toxicity Tests

OBJECTIVETo study the effects of deltamethrin on intracellular free Ca2+ concentration and apoptosis in rat neural cells.

METHODSWister rats were randomly divided into 4 groups(3 treated groups and 1 control). Intracellular free Ca2+ concentration in rat neural cells was measured by using the fluorescent Ca2+ indicator Fura-2/AM. Apopotic rate of neural cells was measured by using FACS420 Flow Cytometer.

RESULTSIntracellular free Ca2+ concentration at 5 h after deltamethrin exposure [hippocampus: (389.94 +/- 43.64) nmol/L, cerebral cortex: (449.33 +/- 23.23) nmol/L], at 24 h[hippocampus: (340.47 +/- 32.36) nmol/L, cerebral cortex: (311.62 +/- 25.48) nmol/L] and at 48 h[hippocampus: (287.13 +/- 24.29) nmol/L, cerebral cortex: (346.55 +/- 36.87) nmol/L] were all higher than those of the control group[hippocampus: (203.24 +/- 18.53) nmol/L, cerebral cortex: (226.85 +/- 14.81) nmol/L, P < 0.01]; Apoptotic rate in neural cells 24 h and 48 h later [hippocampus: (8.45 +/- 1.02)%, (9.44 +/- 1.14)%, cerebral cortex: (7.90 +/- 0.49)%, (8.01 +/- 0.87)%] were also higher than those of the control group[hippocampus: (2.97 +/- 0.36)%, cerebral cortex: (3.50 +/- 0.48)%, P < 0.01)] and increased with time prolonged.

CONCLUSIONExposure to high dose of deltamethrin would interfere with intracellular free Ca2+ concentration and apoptotic rate in rat neural cells, suggesting that there may be certain relation between them.

Animals ; Apoptosis ; drug effects ; Calcium ; metabolism ; Cerebral Cortex ; drug effects ; metabolism ; pathology ; Flow Cytometry ; Hippocampus ; drug effects ; metabolism ; pathology ; Insecticides ; toxicity ; Neurons ; cytology ; drug effects ; metabolism ; Nitriles ; toxicity ; Pyrethrins ; toxicity ; Rats ; Rats, Wistar