Effects of bis(2-chloroethyl)sulfide on ATP receptor-mediated responses of the rat vas deferens: possible relationship to cytotoxicity.

Extracellular ATP is a broad-spectrum cytotoxic agent that produces effects via cell surface P2 purinoceptors. The ligand-gated P2X purinoceptor subtype has very high sequence homology with the RP-2 gene, which encodes for apoptosis. The P2X RNA found in rat vas deferens is expressed preferentially by apoptotic thymocytes. P2X purinoceptor-mediated phasic (twitch) motor responses of the isolated rat vas deferens to neurogenic or exogenous ATP were rapidly, specifically and irreversibly potentiated by bis(2-chloroethyl)sulfide (HD 10-100 microM). Both untreated and HD-potentiated neurogenic responses were Ca++ dependent, blocked in the absence of Ca++ plus 0.1 mM EGTA, by the neuronal Ca++ channel blocker omega-conotoxin-MVIIC (3 microM), by the P2 purinoceptor antagonist suramin (100 microM) and by tetrodotoxin (100 nM). HD also potentiated the effects of ATP on isolated guinea pig taenia caecum, where the nucleotide acts at G protein-coupled P2Y purinoceptor subtypes to cause relaxation. HD failed to inhibit the metabolism of ATP by ecto-ATPase in vas deferens or to cause the release of endogenous ATP. Potentiation of the twitch response to electric field stimulation by HD was attenuated or eliminated in tissues excised from rats previously challenged with topically applied HD, suggesting that HD absorbed into the systemic circulation had already effected maximal potentiation of ATP responses before in vitro testing. The physiological consequences of HD-induced potentiation of the extracellular actions of ATP are discussed in relation to apoptosis and necrosis.

Comparison of several oximes against poisoning by soman, tabun and GF.

Three oximes currently being evaluated for adoption as replacement nerve agent therapy by various countries were compared for therapeutic efficacy against the toxic organophosphate inhibitors soman and tabun under a standard set of conditions. These oximes together with PAM-Cl and toxogonin, were also compared for efficacy against GF, an agent weaponized by Iraq. The order of effectiveness against soman was HI-6 greater than HLö-7 greater than pyrimidoxime. HLö-7 was very effective against tabun poisoning while HI-6 and pyrimidoxime were of moderate value. Against GF, HI-6 and HLö-7 were extremely effective, toxogonin was moderately effective, and PAM-Cl and pyrimidoxime were the least effective. HI-6 provided a high level of protection against all of the agents tested as did HLö-7 to a slightly lesser degree. The other oximes suffered from their lack of effects against one or more of the organophosphates.

Distribution of the bispyridinium oxime [14C] HI-6 in male and female rats.

Female rats poisoned with multiple LD50s of soman or tabun have been shown previously to respond to the protective effects of HI-6 more positively than male rats. This present study was designed first to determine the distribution pattern and concentration of [14C] HI-6 in rats, and secondly, to determine the possibility that HI-6 might be located in high concentrations in critical tissues in the female as opposed to the male. To these ends, [14C] HI-6 was administered to groups of male and female rats and its radiolabelled distribution determined by whole body autoradiography and/or by measurement of its actual concentration, by scintillation spectrometry. The experiments were repeated in the presence of 2 x LD50 soman and supporting therapy with atropine. In both sexes, HI-6 levels were highest in the kidney, followed in order by cartilage greater than plasma greater than liver greater than heart greater than or equal to lung greater than or equal to diaphragm greater than brain and spinal cord. The relative distribution in the two sexes was confirmed by both methods and was not significantly altered in the presence of soman and atropine. The lack of a measurable difference in tissue distribution of [14C] HI-6 derived radioactivity between males and females suggested that the hormone-dependent difference in the protective effects previously observed was not due to selective accumulation of [14C] HI-6 in organs believed to be important in its therapeutic activity, such as brain or diaphragm.

Hormone- and dose schedule-dependent protection by HI-6 against soman and tabun poisoning.

The protective ratio produced by HI-6 (with atropine) against soman and tabun poisoning in rats and guinea pigs was determined. The amount of protection afforded by HI-6 decreased with time following poisoning, prompting us to examine the effects of repeated doses of HI-6 (four additional) given over a 5-hr period. In addition, it was determined that HI-6 produced much better protection in female rats than male rats, which led to a study of the hormone dependence of this activity. When in addition to the first dose of HI-6 four additional doses were given over a 5-hr period, the protective ratio, defined as LD50 in treated animals/LD50 in untreated animals, in males against soman, increased from 4.2 to 7.8, and against tabun, from 2.5 to 6.6. A single dose of HI-6 produced a protective ratio in females of 10.5 against soman and 4.3 against tabun, whereas multiple doses increased these values to greater than 27 and 22, respectively. A regimen consisting of gonad removal and long-term treatment with a sex hormone of the opposite gender reversed the sex-related differences in response to the protective effects of HI-6. In addition a single injection of HI-6 (plus atropine), 1 min following either soman or tabun, produced good protective ratios in guinea pigs against both soman (between 4 and 5) and tabun (5.1); however, there was no apparent hormone-dependent effect similar to that obtained in rats. The results demonstrate unequivocal protective effects of HI-6 against tabun and a very dramatic hormone-dependent factor in its activity against either organophosphate.(ABSTRACT TRUNCATED AT 250 WORDS)

Differences in the toxicity of soman in various strains of mice.

The acute toxicity of soman was assessed in eight strains of mice (ALAS, CD-1, C57BL, CF1, CFW, C3H, DBA and BALB/c). In fasted animals the LD50 values for soman varied from 98 micrograms/kg in C57BL mice to 151 micrograms/kg in BALB/c mice. In general in non-fasted mice the soman LD50 was not significantly changed except in ALAS strain where the soman LD50 value increased significantly. The different sensitivities to soman poisoning among the various strains does not appear to be due totally to differences in level of brain acetylcholinesterase. Fasting had no significant effect on the activity of brain acetylcholinesterase and soman toxicity in CD -1 mice whereas, upon fasting ALAS strain mice for 18 hr, there was a 25% decrease in brain acetylcholinesterase which could explain their increased sensitivity to soman however, it is possible that other biochemical changes may also play a role.