Objective: To evaluate the change of blood pressure, ECG and nitric oxide (NO) in rat heat stroke and effects of aminoguanidine (AG) against heatstroke.
Methods: The male SD rats were randomly assigned into 1 of the following 2 groups: control group or AG group. The rats of control group (n = 10) and AG group (n = 10) were exposed to high ambient temperature (41 degrees C, relative humidity 65%) to induce heatstroke, arterial blood pressures, colonic temperature (T(co)), electrocardiograph (ECG) were monitored. The other rats of both groups (both n = 10) were exposed to high ambient temperature (41 degrees C, relative humidity 65%), and the blood samples were taken at 0, 60 min after the start of heat exposure for determination of the plasma NO concentrations.
Results: (1) From 0 min to 50 min after heat exposure, MAPs of two groups were not significantly different, but at about 55 approximately 60 min after the start of heat exposure, MAPs of control group were decreased significantly differently from that of AG group, K value and dicrotic pulse relative height (h(D)/H) were gradually decreased, especially at 40 min after the start of heat exposure, K value of control group decreased significantly comparison with that of AG group; (2) Heart rate (HR) and QT interval of both groups were increased, while PR interval were decreased after the start of heat exposure; (3) T(co) of both groups were increased after the start of heat exposure until T(co) increased to 42 degrees C (the onset of heatstroke), but there was not significantly difference between the two groups; (4) The time of the onset of heatstroke (TOHS) and survival time (ST) of AG group were significantly longer than those of control group; (5) The plasma NO concentrations of the two groups were significantly higher at 60 min than at 0 min after the start of heat exposure, and the plasma NO concentrations of control group were significantly higher than that of AG group at 60 min after the start of heat exposure.
Conclusion: iNOS may contribute to heatstroke, and aminoguanidine can provide protective effects on heatstroke as a selective iNOS inhibitor.