The objective of this study was to evaluate the effects of an
adenosine A1 agonist, phenylisopropyl
adenosine (PIA), on
metamidophos poisoning compared to specific antidotes. Rats were poisoned with
metamidophos (30 mg/kg, oral) and observed for 24 hours. One group received
sodium chloride (1 mL/kg) and four experimental groups received
atropine (5 mg/kg),
pralidoxime (PAM, 20 mg/kg),
atropine/PAM (5/20 mg/kg) or PIA (1 mg/kg) intraperitoneally.
Atropine reduced salivation and prevented respiratory distress when compared to
sodium chloride-treated rats. Treatment with PAM did not cause any suppression of
cholinergic signs.
Atropine and PAM combination prevented salivation, convulsion and respiratory distress. PIA delayed initial time of the salivation, convulsion and time to death. However, PIA was found ineffective against the
metamidophos-induced
cholinergic symptoms and mortality. All treatments, except PIA, lead to survival of these animals.
Acetylcholinesterase (AChE) activity was not normalized by PIA or PAM. PIA prevented
metamidophos-induced diaphragmatic muscle
necrosis as much as PAM. In conclusion, a single dose of PIA was unable to protect the rats from
metamidophos toxicity. Further studies are needed involving a combination of PAM and/or
atropine with repeated doses of PIA to clarify the efficacy of
adenosine agonists in OP
poisoning.