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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 purification of bovine plasma sarinase has been carried out using alcohol precipitation methods and ultracentrifugation. A protein solution was obtained which was 1250 times more active per unit weight of protein than the original plasma. Sixty per cent of this activity was lost on freeze-drying. The electrophoretic pattern of the preparation showed that the material was apparently homogeneous.

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.

By using sarin (isopropyl methylphosphonofluoridate) tagged with P32it has been possible to determine the distribution of the P32in the tissues after injection of sarin solutions or after cutaneous application of sarin vapor. In rabbits the percentage of P32per gram of tissue after injection of sarin P32was found to be higher in lung and kidneys than in other organs. The ratio of the P32in blood to that in the body as a whole was found to decrease with the time after injection. The ratio also varied with the time after cutaneous application of vapor but in this case the results were complicated by the relatively long exposure times compared with the injection times. Cholinesterase determinations carried out on rabbit erythrocytes showed that the Cholinesterase levels dropped precipitously as the P32concentration in the blood increased.

Studies have been made of the penetration of sarin (isopropyl methylphosphonofluoridate) tagged with P32through the skin of rabbits. Sarin vapor at a constant concentration was passed through a plastic cup attached to the clipped bellies of rabbits. Using different sizes of cups it has been found that the L(ct)50 (concentration × exposure time required to kill 50% of the animals exposed) decreased as the exposure area was increased. From these experiments it was possible to determine how absorption through skin varies with area exposed, vapor concentration, and exposure time and to find the approximate 'ct' necessary to kill a rabbit for any area of skin exposed.

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.

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 purification of bovine plasma sarinase has been carried out using alcohol precipitation methods and ultracentrifugation. A protein solution was obtained which was 1250 times more active per unit weight of protein than the original plasma. Sixty per cent of this activity was lost on freeze-drying. The electrophoretic pattern of the preparation showed that the material was apparently homogeneous.

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.

Studies have been made of the penetration of sarin (isopropyl methylphosphonofluoridate) tagged with P32through the skin of rabbits. Sarin vapor at a constant concentration was passed through a plastic cup attached to the clipped bellies of rabbits. Using different sizes of cups it has been found that the L(ct)50 (concentration × exposure time required to kill 50% of the animals exposed) decreased as the exposure area was increased. From these experiments it was possible to determine how absorption through skin varies with area exposed, vapor concentration, and exposure time and to find the approximate 'ct' necessary to kill a rabbit for any area of skin exposed.

By using sarin (isopropyl methylphosphonofluoridate) tagged with P32it has been possible to determine the distribution of the P32in the tissues after injection of sarin solutions or after cutaneous application of sarin vapor. In rabbits the percentage of P32per gram of tissue after injection of sarin P32was found to be higher in lung and kidneys than in other organs. The ratio of the P32in blood to that in the body as a whole was found to decrease with the time after injection. The ratio also varied with the time after cutaneous application of vapor but in this case the results were complicated by the relatively long exposure times compared with the injection times. Cholinesterase determinations carried out on rabbit erythrocytes showed that the Cholinesterase levels dropped precipitously as the P32concentration in the blood increased.

The enzymatic hydrolysis of sarin is apparently a single first-order reaction. There is no evidence of different reaction rates for the two possible optical isomers of sarin. During both the enzymatic and the non-enzymatic hydrolyses, sarin appears to be detoxified somewhat more rapidly than the manometric results would indicate. However, the detoxification parallels the manometric results sufficiently to stand in contrast to results obtained using tabun.

The enzymatic hydrolysis of sarin is apparently a single first-order reaction. There is no evidence of different reaction rates for the two possible optical isomers of sarin. During both the enzymatic and the non-enzymatic hydrolyses, sarin appears to be detoxified somewhat more rapidly than the manometric results would indicate. However, the detoxification parallels the manometric results sufficiently to stand in contrast to results obtained using tabun.

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