EFFECT OF REPEATED EXPOSURES OF GB VAPOR ON ERYTHROCYTE AND BRAIN CHOLINESTERASESIN RATS

¹ Chemical Corps Medical Laboratories, Army Chemical Center, Maryland

The rate of decrease in erythrocyte ChE activity in rats exposed 63 times to a Ct of 50 mgm. min./m.³ was 3.6 ± 0.3 per cent per day for about the first 17 days, after which no further reduction occurred. During the corresponding period of exposure, brain ChE decreased at a rate of about 1.2 ± 0.5 per cent per week, which is a drop from 100 to 92 ± 2 per cent after 49 days.

Increasing the Ct from 75 to 150 mgm. min./m.³ caused a further drop in erythrocyte ChE activity, after which the rate of decrease was very small, even when the Ct's were increased in steps to 508 mgm. min./m.³. The rate of depression of brain ChE activity began to increase after attaining a daily Ct of 100 mgm. min./m.³. The rate of fall became more pronounced during and after a daily Ct exposure of 225 mgm.min./m.³

Rats initially exposed to a Ct of 150 mgm. min./m.³, which was raised to 225 mgm. min./m.³, showed a decrease in erythrocyte ChE activity at a rate of about 23 per cent per day for about three days, after which no further marked reduction occurred despite an increase in Ct to 225 mgm. min./m.³. The brain ChE activity decreased at a rate of approximately one per cent per day under the conditions of this test.

The rate of recovery of erythrocyte ChE activity after 35 exposures to daily Ct's of 50 mgm. min./m.³ was 1.5 ± 0.3 per cent per day. Brain ChE activity, which at the conclusion of the exposure period was 94 ± 2 per cent of the average control value, did not show any significant recovery after 38 days.