Distinct pathophysiological mechanisms of Heterometrus laoticus and Lychas mucronatus scorpion venoms on cardiovascular and renal functions.

BACKGROUND

Heterometrus laoticus and Lychas mucronatus are widely distributed in Southeast Asia, yet their pathophysiological effects of both venoms remain poorly characterized due to low human fatality rates. This study compared their venom compositions and acute cardiovascular and renal effects.

METHODS

Anesthetized male New Zealand White rabbits were monitored for blood pressure (BP), heart rate (HR), and renal clearance following intravenous administration of crude venom (0.5 mg/kg). Venom components were identified via LC-MS/MS, and hematological/biochemical parameters were assessed.

RESULTS

H. laoticus venom induced a rapid, transient hypotension (p < 0.05), followed by a mild, prolonged hypotensive phase (up to 120 min). Conversely, L. mucronatus venom elicited a biphasic response: initial transient hypotension followed by significant hypertension (p < 0.05) and a subsequent terminal hypotensive stage. Renal hemodynamic changes in both groups were secondary to these systemic cardiovascular fluctuations.

CONCLUSIONS

LC-MS/MS revealed that the neurotoxin-rich profile (KTx and NaTx) of L. mucronatus drives vasoconstriction and hypertension. In contrast, the higher PLA₂ content in H. laoticus mediates cytotoxic-like effects, resulting in vasodilation and hypotension. These distinct molecular mechanisms suggest that clinical management should be species-specific, even for venoms traditionally considered "mild."