Cartap is extensively used to control agricultural pests. Pertinent literatures have
indicated that it causes no eye irritation [D.E. Ray, Insecticides derived from plants
and other organisms, in: W.J. Hayes, E.R. Laws (Eds.), Handbook of Insecticide Toxicology,
Classes of Insecticides, vol. 2, Academic Press, New York, 1991, p. 611; C. Tomlin,
Cartap, in: C. Tomlin (Ed.), The Insecticide Manual, 12th ed., British Crop Protection
Council, Surrey, UK, 2000, p. 144]; however, the instillation of a little cartap through
the eye has caused death in rabbits. The aim of this study was to determine the ocular
toxicity of cartap in New Zealand White rabbits. Cartap was directly instilled into
the low conjunctival sac of eyes, at doses of 0, 5, 7.5, 10 and 12.5 mg/kg body weight.
The changes in the enzymes and isoenzymes of creatine kinase (CK), lactate dehydrogenase
(LD), as well as pathological changes in the muscles of the heart, thigh and diaphragm
were determined in the cartap-treated rabbits. Moreover, the neuromuscular effect
of cartap was examined using the isolated rabbit phrenic-nerve diaphragm model. The
results indicated that rabbits developed severe signs and they died within 20 min
of ocular instillation. The ocular LD50 of cartap was 8.1 mg/kg body weight. Treatment
with cartap increased the activities of CK and LD enzymes and their isoenzymes, CK-1,
CK-2, and CK-3 in serum, and CK-3 and LD-5 in the diaphragm. Microscopically, hypercontraction
bands and the rupture of myofibers of the diaphragm were observed in dead rabbits.
Cartap did not affect nerve-evoked twitch but induced irreversible contracture and
twitch depression on the isolated rabbit's diaphragm. These results indicate that
the rabbit is susceptible to cartap toxicity; the effect of cartap caused contracture
and damage to the diaphragm might play a pivotal role in respiratory paralysis and
death of rabbits during intoxication.