Objectives: This study was designed to compare vascular contractile and relaxing responses to G-protein coupled receptor agonists among the different regions of arteries following heat stress in rats.
Methods: Heat exposure was performed by increasing the internal temperature of the rats to 42 degrees C for 15 min. After heat stress for 48 h, a myograph system was used to monitor the contractile responses in rat renal, femoral and mesenteric arteries to agonists of endothelin type B (ET(B)) receptor, endothelin type A (ET(A)) receptor, serotonin receptor and alpha-adrenoceptor, respectively. In addition, calcitonin gene-related peptide (CGRP)-induced vasodilation was studied.
Key findings: The results showed that heat stress induced decreased contractions mediated by alpha-adrenoceptors and serotonin receptors (at lower concentration), while it increased contraction mediated by endothelin ET(B) receptors and enhanced relaxation mediated by CGRP receptors in the renal artery. Heat stress increased contractions mediated by endothelin ET(B) receptors, endothelin ET(A) receptors and alpha-adrenoceptors in the femoral artery. In the mesenteric artery, heat stress increased contractions mediated by endothelin ET(B) and serotonin receptors and relaxation mediated by CGRP receptors.
Conclusions: The vasomotor responses to the G-protein coupled receptor agonists with altered vascular contractions and relaxations were different in rat renal, femoral and mesenteric arteries after heat stress. This might have contributed to the redistribution of blood flow and aids understanding of the preconditioning phenomenon.