Erythrocyte and Plasma Cholinesterase Activity in Male and Female Rhesus Monkeys before and after Exposure to Sarin

The rhesus monkey (Macaca mulatta) has a menstrual cycle similarto the human. Differences in hormone levels have been demonstratedbetween the sexes and in females during the menstrual cyclebut these differences in terms of organophosphorus toxicityhave not been explored. Plasma cholinesterase (ChE/BuChE) anderythrocyte (RBC) acetylcholinesterase (AChE) activity weremeasured before and after exposure to the organophosphorus compoundsarin (11 µg/kg, iv; 0.75 LD50) in six male and six femalerhesus monkeys. After baseline measurements were obtained, sarinwas administered to atropinized monkeys to determine in vivodifferences between the sexes in their response to sarin. Withthe baseline values, the intraanimal and intragroup BuChE/AChEvariations were found to be minimal. Following sarin intoxicationand 2-PAM treatment no significant differences were seen betweenthe sexes in the rate of reactivation of BuChE or AChE by 2-PAM.The rate of aging of sarin phosphonylated RBC AChE between thesexes was also similar. De novo regeneration of RBC AChE andplasma BuChE after sarin intoxication was different betweenthe male and female monkeys. The female plasma BuChE recoveryrate was 48% slower than the male recovery rate, while the early(first 63 days) RBC AChE recovery rate was 24.5% faster in thefemales. In conclusion, there probably are not any clinicallysignificant differences between male and female rhesus monkeysacutely intoxicated with sarin. However, on subsequent exposureclinical differences may be observed due to substantial differencesin the rate of de novo synthesis of both plasma BuChE and RBCAChE.