Phoneutria nigriventer
spider bite causes
priapism, an effect attributed to the
peptide toxins
Tx2-5 and
Tx2-6 and involving
nitric oxide.
Tx2-6 (MW = 5287) is known to delay the inactivation of
Sodium channels in the same fashion as many other
venom toxins. In the present study we evaluated the i.p. dose that induces
priapism and the other symptoms in mice. Animals killed by the toxin or crude
venom (0.85 mg/kg) were autopsied and a pathological study of brain, lung, kidney, liver and heart was undertaken using standard techniques. The same protocol was employed with animals injected with crude
venom. Results showed that
priapism is the first sign of intoxication, followed by piloerection, abundant salivation and
tremors. An i.p. injection of about 0.3 μg/kg induced only
priapism with minimal side-effects. The most remarkable histological finding was a general vascular congestion in all organs studied. Penis showed no
necrosis or damage. Lungs showed vascular congestion and alveolar
hemorrhage. Heart showed also sub-endothelial
hemorrhage. Brain showed only a mild
edema and vascular congestion. Results obtained with crude
venom closely resemble those of purified toxin. We conclude that
Tx2-6 have profound effects on the vascular bed especially in lungs and heart, which may be the cause of death. Interestingly brain tissue was less affected and the observed
edema may be attributed to respiratory impairment. To the best of our knowledge this is the first histopathological investigation on this toxin and
venom suggesting a possible cause of death.