A comparison of in vivo and in vitro rates of aging of soman-inhibited erythrocyte acetylcholinesterase in different animal species.

This study was conducted to assess differences in the rate of aging of soman-inhibited erythrocyte (RBC) acetylcholinesterase (AChE) from different species and to determine whether the rate of aging in vitro approximates that in vivo following a single exposure to soman. The logarithm of the percentage RBC AChE reactivated by 2-PAM after soman exposure was plotted as a function of time. Linear regression analysis was used to determine the half-time (t1/2) for aging. In the in vivo experiments, the rapidity of aging increased from rat to guinea pig to marmoset; the corresponding t1/2 values (mean +/- standard error) were 8.6 (+/- 0.94) min, 7.5 (+/- 1.7) min and 0.99 (+/- 0.10) min. The in vitro values of t1/2 in marmoset and guinea pig were 1.1 (+/- 0.08) min and 8.0 (+/- 0.82) min, respectively. Other t1/2 values computed for in vitro experiments were 1.4 (+/- 0.11) min for cynomolgus monkeys and 0.88 (+/- 0.03) min for squirrel monkeys. The results indicate that, for marmoset and guinea pig, the in vitro values closely approximate the in vivo. Since aging of soman-inhibited human and monkey RBC AChE occurs rapidly (1 min) in vitro, it is reasonable to assume that in man rapid aging will be crucial in delimiting successful treatment of soman intoxication.