OBJECTIVETo explore the inhibitory effects of highly toxic organophosphorus compound and its substitute (methamidophos and acephate) on acetylcholinesterase (AChE) and their toxic mechanisms.

METHODSEllman method was used to measure AChE activity in vitro and vivo.

RESULTSAcephate and methamidophos could directly inhibit AChE activities in human erythrocyte membrane and rat brain synatosomal membrane in dose- and time-dependent manners in vitro, and this effect was irreversible. The IC50 of acephate and methamidophos affecting human erythrocyte membrane and rat synatosomal membrane were approximately 10(-4) mol/L and 10(-5) mol/L respectively and the Ki were 10(2) mol.L-1.min-1 and 10(3) mol.L-1.min-1 respectively. In vivo, after rats being administered with them for 5 d, the inhibitory rate of AChE activities in blood were increased to 68.24% and 54.80% respectively. When rats being administrated with acephate, there was 31.68% of inhibition on the brain stem, but no significant inhibition in other brain region was noticed, while methamidophos had a strong inhibitory effect on the activity of AChE in all brain regions, especially the cerebellum and brain-stem(71.51% and 61.85% respectively).

CONCLUSIONAcephate and methamidophos could directly inhibit the AChE activities in vitro, but the inhibition degree was different. In vivo, both could also inhibit AChE activities in blood. The difference in inhibition on brain regions may be one of the reason of various toxic effect of them.

Animals ; Cholinesterase Inhibitors ; toxicity ; Erythrocyte Membrane ; enzymology ; Humans ; Insecticides ; toxicity ; Organothiophosphorus Compounds ; toxicity ; Phosphoramides ; Rats ; Synaptosomes ; enzymology

To explore the action mechanism of lithium in the brain, the author investigated the effects of lithium on Na-K ATPase and Ca ATPase in rat brain synaptosomes prepared from forebrains by the method of Booth and Clark. The activities of Na-K ATPase and Ca ATPase were assayed by the level of inorganic phosphate liberated from the hydrolysis of ATP. Lithium at the optimum therapeutic concentration of 1 mM decreased the activity of Na-K ATPase from the control value of 19.08 +/- 0.29 to 18.27 +/- 0.10 micromoles Pi/mg protein/h and also reduced the activity of Ca ATPase from 6.38 +/- 0.12 to 5.64 +/- 0.12 micromoles Pi/mg protein/h. The decreased activity of Na-K ATPase will decrease the rate of Ca2+ efflux, probably via an Na-Ca exchange mechanism and will increase the rate of Ca2+ entry by the depolarization of nerve terminals. The reduced activity of Ca ATPase will result in the decreased efflux of Ca2+. As a Conclusion, it can be speculated that lithium elevates the intrasynaptosomal Ca2+ concentration via inhibition of the activities of Na-K ATPase and Ca ATPase, and this increased [Ca2+]i will cause the release of neurotransmitters and neurological effects of lithium.
Animal ; Brain/*enzymology ; Ca(2+)-Transporting ATPase/*antagonists & inhibitors ; Lithium/*pharmacology ; Male ; Na(+)-K(+)-Exchanging ATPase/*antagonists & inhibitors ; Rats ; Rats, Sprague-Dawley ; Synaptosomes/*enzymology

AIMTo study the effects of sodium magnesium fructose diphosphate (SMFD) on free calcium concentration and nitric oxide synthase activity of ischemic synaptosome, so as to explore the protective mechanisms of SMFD on cerebral ischemia.

METHODSThe synaptosomes from normal rat brain were prepared by phase partition and cultured with oxygen-glucose deprivation to establish ischemic synaptosome model. The intrasynaptosomal free calcium concentration and nitric oxide synthase activity were detected separately after the synaptosomes were co-incubated with SMFD (1.3 mmol.L-1) or fructose-1, 6-diphosphate (FDP, 4.0 mmol.L-1) for 60 min.

RESULTSSMFD decreased the free calcium concentration and reduced the activity of nitric oxide synthase (NOS) of ischemic synaptosomes. Its effects were more powerful than those of FDP.

CONCLUSIONSMFD may protect neurons from ischemic injury by preventing intracellular Ca2+ overload and inhibiting the activity of nitric oxide synthase.

Animals ; Brain Ischemia ; enzymology ; metabolism ; Calcium ; metabolism ; Chelating Agents ; pharmacology ; Fructosediphosphates ; pharmacology ; Magnesium ; chemistry ; Male ; Nitric Oxide Synthase ; drug effects ; metabolism ; Rats ; Rats, Wistar ; Sodium ; chemistry ; Synaptosomes ; metabolism

OBJECTIVETo explore changes of neuronal calcium channel following brain damage induced by injection of pertussis bacilli in rats, and to investigate the relationship between cytosolic free calcium concentration ([Ca(2+)](i)) in the synaptosome and Ca(2+)-ATPase activities of mitochondria.

METHODSThe level of [Ca(2+)](i) in the synaptosome and Ca(2+)-ATPase activities of mitochondria in the acute brain damage induced by injection of pertussis bacilli (PB) in rat was determined and nimodipine was administrated to show its effects on [Ca(2+)](i) in the synaptosome and on alteration of Ca(2+)-ATPase activity in the mitochondria. Seventy-three rats were randomly divided into four groups, ie, normal control group (Group A), sham-operation control group (Group B), PB group (Group C) and nimodipine treatment group (Group D).

RESULTSThe level of [Ca(2+)](i) was significantly increased in the PB-injected cerebral hemisphere in the Group C as compared with that in the Group A and the Group B at 30 minutes after injection of PB. The level of [Ca(2+)](i) was kept higher in the 4 hours and 24 hours subgroups after the injection in the Group C (P<0.05). In contrast, the Ca(2+)-ATPase activities were decreased remarkably among all of the subgroups in the Group C. Nimodipine, which was administered after injection of PB, could significantly decrease the [Ca(2+)](i) and increase the activity of Ca(2+)-ATPase (P<0.05).

CONCLUSIONSThe neuronal calcium channel is opened after injection of PB. There is a negative correlation between activities of Ca(2+)-ATPase and [Ca(2+)](i). Nimodipine can reduce brain damage through stimulating the activities of Ca(2+)-ATPase in the mitochondria, and decrease the level of [Ca(2+)](i) in the synaptosome. Treatment with nimodipine dramatically reduces the effects of brain damage induced by injection of PB.

Analysis of Variance ; Animals ; Bordetella pertussis ; Brain Injuries ; metabolism ; Calcium ; metabolism ; Calcium Channel Blockers ; pharmacology ; Calcium-Transporting ATPases ; metabolism ; Cytosol ; metabolism ; Mitochondria ; enzymology ; Nimodipine ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Synaptosomes ; metabolism