Vascular Protection with Less Activation Evoked by Progressive Thermal Preconditioning in Adrenergic Receptor-Mediated Hypertension and Tachycardia

Abstract

Thermal preconditioning may afford cardiovascular protection against oxidative injuries. However, hypertension and taychardia by sympathetic stimulation frequently occur during 420C 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 degrees C bath water. Treatment with phentolamine (alpha-adrenergic blocker), propranolol (beta-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 FeCl3-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. PTP-induced attenuation of changes in hemodynamic parameters was via alpha- and beta-adrenergic inhibition. FeCl3 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 FeCl3-induced femoral TTO to a similar degree. PTP may provide vascular protection against oxidative injuries with less activation in alpha-adrenergic receptor-mediated hypertension and beta-adrenergic receptor-mediated tachycardia.