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Effect in vitro of propoxur on the specific activity of calcium stimulated ATPase and calcium uptake was studied in the rat brain synaptosomes. The data suggest that propoxur might disrupt the synaptic function by altering the calcium dependent ATP hydrolysis and calcium uptake in the central nervous system.

Kinetic study of succinate dehydrogenase (SDH) was studied in the brain of albino rat to elucidate the interaction of benthiocarb, an organocarbamate with oxidative metabolism. The significant decrease in maximal velocity (Vmax) without appreciable change in Michaelis-Menten constant (Km) indicates that benthiocarb did not affect or interfere with succinate oriented sites on the enzyme and the inhibition is of a classical non-competitive type.

Substrate kinetics of succinate dehydrogenase (EC 1.3.99.1) were studied in the brain of control and dieldrin-treated albino rats. Dieldrin inhibited the enzyme activity to various degrees and also altered the Michaelis-Menten constant (Km) of the enzyme. Activation energy values (delta E) were increased, suggesting decreased maximal velocity Vmax, and the high Km obtained for the enzyme also revealed decreased enzyme-substrate affinity and masking of active sites by dieldrin.

Effects in vitro of benthiocarb on rat brain Mg2+-ATPase were studied to elucidate the interaction of benthiocarb with Mg2+-ATPase. Based on IC50 values, it was evident that Mg2+-ATPase was sensitive to benthiocarb. Non-competitive inhibition with respect to activation by ATP was indicated by decreased maximal velocity (V) without change in Michaelis Menten constant (Km). It was also noted that pyridine-2-aldoxime (30 microM), pyridine-4-aldoxime (35 microM) and L-cysteine (90 microM) neutralized the inhibition of benthiocarb (8 microM).

Effects of repeated administration of benthiocarb on the nitrogen metabolism of hepatic and neuronal systems have been studied. Repeated benthiocarb treatment was associated with significant decrease in proteins with a concomitant increase in free amino acids (FAA) and specific activity levels of proteases suggesting impaired protein synthesis or elevated proteolysis. The glycogenic aminotransferases showed a significant elevation in both the tissues indicating high feeding of ketoacids into oxidative pathway for efficient operation of TCA cycle to combat energy crisis during induced benthiocarb stress. However, the activity levels of branched-chain aminotransferases decreased suggesting their reduced contribution of intermediates to TCA cycle. A comparative evaluation of the activity levels of ammonogenic enzymes, AMP deaminase, adenosine deaminase and glutamate dehydrogenase (GDH) indicated that ammonia was mostly contributed by nucleotide deamination rather than by oxidative deamination. GDH exhibited reduced activity due to low availability of glutamate. In accordance with increased levels of urea, the activity levels of arginase, a terminal enzyme of urea cycle was increased suggesting increased urea cycle operation in order to combat the increased ammonia content. As the presence of urea cycle in the brain is rather doubtful, the conversion of ammonia to glutamine for the synthesis of GABA is envisaged in brain whereas in liver, excess ammonia was converted to urea through ornithine-arginine reacting system. The increased glutaminase activity observed during benthiocarb intoxication is accounted for counteracting acidosis or maintenance of metabolic homeostasis. Arginase, a terminal enzyme of ornithine cycle showed increased activity denoting the efficient potentiality of tissues to avert ammonia toxicity. The changes observed in tissues of rat administered with benthiocarb reflects a shift in nitrogen metabolism for efficient mobilization of end products of protein catabolism.

The effects in vivo and in vitro of benthiocarb, an organocarbamate, on acetylcholinesterase (AChE) activity and its recovery in vitro in the brain of the freshwater fish Sarotherodon mossambicus have been studied. Findings revealed that the specific activity of AChE was inhibited both in vivo and in vitro in a concentration-dependent manner. Of the different modulators tested, dexamethasone (0.72 mg), prednisolone (0.74 mg), testosterone (0.9 mg), and ADP (9.5 mg) were found to neutralize the inhibitory effect (IC50 = 0.30 microM) of benthiocarb on AChE.

In this study we report that uptake of 45calcium(45Ca) by neonate rat brain synaptosomes was disrupted during benthiocarb poisoning. This altered 45Ca uptake suggests possible derangement in the regulation of ionic pumps, ATP hydrolysis, neurotransmitter release and other calcium dependent phenomena.

Metabolic diversions in oxidative metabolism of hepatic and neuronal systems of rat were noticed during induced benthiocarb stress. The inhibition of dehydrogenases indicates disturbed mitochondrial integrity, and reduction in cytochrome-C-oxidase suggests possible respiratory distress. The drop in ATPases and PNPPase indicates the prevalence of energy crisis. The increased specific activities of NADP+ dependent dehydrogenases suggests augmented lipid biosynthesis in the wake of impaired oxidative metabolism.

Benthiocarb effect on rat brain acetylcholinesterase (AChE) has been studied to know the toxic effects of benthiocarb on mammalian cholinergic systems. From the study, it has been observed that the inhibition of AChE activity increased with increase in treatment period which is attributed to the cumulative effects of benthiocarb on AChE activity. The kinetic study revealed that there is a slight increase in Km and a marked decrease in Vmax which accounts for the non-competitive inhibition of enzyme during benthiocarb intoxication.