The acute toxicity of
carbophenothion to three age classes of Artemia salina was evaluated. An increase in toxicity of
carbophenothion was found following longer development of A. salina. The effect of pretreatment with the nonselective
muscarinic antagonist atropine, the two reversible
acetylcholinesterase-inhibitors physostigmine and
pyridostigmine, and the
cholinesterase-reactivating
oxime 2-pyridine
aldoxime methochloride (2-PAM) on
carbophenothion-induced lethality in 24-h-old A. salina was also investigated. The lethal action of
carbophenothion was completely prevented by pretreatment of A. salina with
2-PAM.
Atropine and
pyridostigmine afforded a maximal protection of approximately 87% and 72%, respectively, compared to control values. In contrast,
physostigmine was ineffective. The inhibitory effects of combinations of 10(-5) M
atropine with
physostigmine,
pyridostigmine, or
2-PAM were greater than those elicited by either
drug alone, with the maximum protection afforded being 92.58%, 100%, and 100%, respectively. In the presence of 10(-7) M
atropine, neither
pyridostigmine nor
2-PAM provided additional inhibition of the lethality compared to that with either
drug alone, whereas the protection afforded by 10(-7) M
atropine plus
physostigmine increased as the concentration of
carbamate increased (up to 10(-3) M). Pretreatment with
pyridostigmine or
physostigmine plus
2-PAM (10(-6) M) slightly enhanced the maximal inhibition of
carbophenothion lethality compared to that with either
drug alone. It is suggested that the most active combined pretreatment studied here was
physostigmine plus
atropine.