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The effect in rabbits of the sarinase levels of liver and plasma, and of cholinesterase levels of plasma on survival after repeated intraperitoneal or subcutaneous doses of sarin has been investigated. When the intraperitoneal route was used a significant correlation was found between liver sarinase and survival. Survival after subcutaneous injection was not affected by the liver sarinase. No correlation was found between plasma sarinase or plasma cholinesterase and survival for either the intraperitoneally or subcutaneously injected rabbits.

The enzymes which hydrolyze isopropyl methylphosphonofluoridate (sarin) and ethyl N, N-dimethylphosphoramidocyanidate (tabun) have been studied. Michaelis–Menten constants and activation energies have been estimated and enzyme stability has been studied. The distribution of the enzymes in mammalian tissues has been examined. It is concluded that from each source the same enzyme is responsible for the hydrolysis of sarin and tabun but that this enzyme shows variations from source to source. That there are mixtures of very similar enzymes, having a composition in amounts characteristic of the source, is also considered possible.

The cells of the liver and kidneys from three species known to be comparatively susceptible to sarin (rabbit, guinea pig, and monkey) and two species known to be less susceptible (rat and mouse) have been fractionated into their cell constituents (nuclei, mitochondria, microsomes, and non-particulate fraction). Each fraction has been tested for sarinase activity. The non-particulate fraction had the highest activity, the microsomes the second highest, the mitochondria the third highest, and the nuclei the lowest. The significance of the differences found in the distribution of sarinase activity in the cell fractions is discussed.Monkey cell fractions were also tested with ethyl N,N-dimethylphosphoramidocyanidate (tabun) as the substrate. The results were similar to those obtained with sarin, suggesting that the same enzyme was responsible for the hydrolysis of both substrates.