Response of
cholinesterase to dermal exposure of acute, single and multiple doses of
Bromophos in the female rat has been studied. Dose-response studies (50-4000 mg/kg
body weight, 24 h exposure) showed that plasma
cholinesterase was most sensitive to inhibition in vivo, followed by the brain and erythrocyte
acetylcholinesterase. The ID50 values for the in vivo
cholinesterase inhibition were 10.1, 576.1 and 1938.0 mg/kg
body weight for the plasma, brain and erythrocytes, respectively. In time-course studies after a single sublethal dose of 1000 mg/kg
body weight (24 h) of
Bromophos, the serum and brain
cholinesterase were rapidly inhibited reaching a maximum at 16 h. Recovery was complete in the case of serum at 14 days post-exposure, whereas the brain
enzyme was not fully recovered at 21 days. In a subacute study, daily dermal application of 50 mg/kg
body weight of
Bromophos for 5 and 10 days, resulted in high inhibition of the serum
cholinesterase and brain
acetylcholinesterase, the former being more marked which was reversible after 10 or 15 days of post-exposure period. Very low levels of dermal exposure of
Bromophos (10-50 mg/kg
body weight) for 17 days caused pronounced depression of serum
cholinesterase which completely recovered in 15 days after cessation of exposure suggesting that the serum
cholinesterase could serve as the most sensitive diagnostic
indicator of
Bromophos exposure.