Cardiorespiratory evaluation of juvenile rats experimentally envenomed with Tityus serrulatus venom

Abstract

Accidental envenomation caused by Tityus serrulatus scorpions is very common in Brazil and may result in serious cardiorespiratory alterations that are frequently fatal to children. In the present study, the effects of T. serrulatus venom on the cardiorespiratory system of recently weaned male Wistar rats were evaluated. Fifteen animals were distributed into three groups (n = 5). The control group A received 400 μL ultrapure water by subcutaneous injection, while the experimental groups B and C were injected with scorpion venom (100 and 450 μg, respectively, in 400 μL water). Electrocardiogram (ECG) traces were obtained prior to the experiment, at five-minute intervals up to 30 minutes after treatment. At 40 minutes after envenomation, the animals had severe acute symptoms and were subsequently anesthetized for blood collection by means of intracardiac puncture. Biochemical profiles for the cardiac muscle were established by colorimetric analysis of creatine kinase (CK) and CK-MB isoenzyme. Semiquantitative analysis of troponin was performed using the immunochromatographic assay. Following euthanasia, the lungs and hearts were removed and subjected to histopathological examination. All experimental animals had ECG alterations compatible with electrolytic imbalance, myocarditis and alterations of the cardiac conduction system. Envenomed animals had accentuated bradycardia at 25 and 30 minutes after venom inoculation. All experimental animals had myocardial lesions, which were confirmed by increased serum levels of CK and CK-MB, although there were no alterations in the serum concentration of troponin. Pulmonary hemorrhage was detected in whole lungs and microscopically confirmed by the presence of congested capillaries and erythrocytes in the alveolar parenchyma. In conclusion, T. serrulatus venom caused great cardiorespiratory damage to weaned rats.

Clinical consequences of Tityus bahiensis and Tityus serrulatus scorpion stings in the region of Campinas, southeastern Brazil

“…The precise reasons for this age-related difference in toxicity remain unclear, although possible explanations include a greater venom dose/body weight ratio in children compared to adults and age-related variations in sensitivity to the venom. Although experimental studies have also found differences in the lethality, cardiorespiratory responses and pharmacokinetics of T. serrulatus venom in young compared to adult rats (Nunan et al, 2001(Nunan et al, , 2003(Nunan et al, , 2004Pinto et al, 2010), the relevance of these findings to envenomation in humans is uncertain. The marked difference in the severity of envenomation (and lethality) between T. serrulatus and T. bahiensis in humans contrasts with the lack of significant differences in the lethality of venoms from these two species in standard LD 50 tests in laboratory animals (Bücherl, 1953;Nishikawa et al, 1994).…”