Vascular protection with less activation evoked by progressive thermal preconditioning in adrenergic receptor-mediated hypertension and tachycardia

Thermal preconditioning may afford cardiovascular protection against oxidative injuries. However, hypertension and taychardia by sympathetic stimulation frequently occur during 42° C whole body thermal preconditioning (TP). We aimed to develop a modified TP to achieve cardiovascular protection with to reduced cardiovascular stimulation in the rat. We used a progressive thermal preconditioning (PTP) with three-step 5-min immersion of male Wistar rats in 42° C bath water. Treatment with phentolamine (α-adrenergic blocker), propranolol (β-adrenergic blocker) and atropine (muscarinic cholinergic blocker) was used to evaluate the effect and mechanism of PTP on systemic hemodynamics. Protective function was evaluated by FeCl ₃ -induced acute femoral arterial occlusion (TTO) and heat shock protein 70 expression. Our results show that TP enhanced body temperature, hypertension and tachycardia. However, PTP produced a similar increase in body temperature with significantly less enhancement of hypertension and tachycardia when compared with the TP group. TP- or PTP-induced increase of blood pressure and heart rate was inhibited by phentolamine and propranolol, respectively. PTPinduced attenuation of changes in hemodynamic parameters was via α- and β-adrenergic inhibition. FeCl ₃ induced femoral arterial injury indicated by TTO at 416 ± 51 sec in the control rats. After 24 h of TP or PTP treatment with or without adrenergic blocker treatment, TP or PTP upregulated similar femoral arterial heat shock protein 70 expression and significantly (P < 0.05) delayed FeCl ₃ -induced femoral TTO to a similar degree. PTP may provide vascular protection against oxidative injuries with less activation in α-adrenergic receptor-mediated hypertension and α-adrenergic receptor-mediated tachycardia.