Exhaustive swimming differentially inhibits P2X1 receptor- and α1-adrenoceptor-mediated vasoconstriction in isolated rat arteries.

AIM: To investigate the effects of exhaustive swimming exercise on P2X1 receptor- and α1-adrenoceptor-mediated vasoconstriction of different types of arteries in rats. METHODS: Male Wistar rats were divided into 2 groups: the sedentary control group (SCG) and the exhaustive swimming exercise group (ESEG). The rats in the ESEG were subjected to a swim to exhaustion once a day for 2 weeks. Internal carotid, caudal, pulmonary, mesenteric arteries and aorta were dissected out. Isometric vasoconstrictive responses of the arteries to α,ß-methylene ATP (α,ß-MeATP) or noradrenaline (NA) were recorded using a polygraph. RESULTS: The exhaustive swimming exercise did not produce significant change in the EC(50) values of α,ß-MeATP or NA in vasoconstrictive response of most of the arteries studied. The exhaustive swimming exercise inhibited the vasoconstrictive responses to P2X1 receptor activation in the internal carotid artery, whereas it reduced the maximal vasoconstrictive responses to α1-adrenoceptor stimulation in the caudal, pulmonary, mesenteric arteries and aorta. The rank order of the reduction of the maximal vasoconstriction was as follows: mesenteric, pulmonary, caudal, aorta. CONCLUSION: Exhaustive swimming exercise differentially affects the P2X1 receptor- and α1-adrenoceptor-regulated vasoconstriction in internal carotid artery and peripheral arteries. The ability to preserve purinergic vasoconstriction in the peripheral arteries would be useful to help in maintenance of the basal vascular tone during exhaustive swimming exercise.

Physiological significance of P2X receptor-mediated vasoconstriction in five different types of arteries in rats.

P2X(1) receptors, the major subtype of P2X receptors in the vascular smooth muscle, are essential for α,ß-methylene adenosine 5'-triphosphate (α,ß-MeATP)-induced vasoconstriction. However, relative physiological significance of P2X(1) receptor-regulated vasoconstriction in the different types of arteries in the rat is not clear as compared with α(1)-adrenoceptor-regulated vasoconstriction. In the present study, we found that vasoconstrictive responses to noncumulative administration of α,ß-MeATP in the rat isolated mesenteric arteries were significantly smaller than those to single concentration administration of α,ß-MeATP. Therefore, we firstly reported the characteristic of α,ß-MeATP-regulated vasoconstrictions in rat tail, internal carotid, pulmonary, mesenteric arteries, and aorta using single concentration administration of α,ß-MeATP. The rank order of maximal vasoconstrictions for α,ß-MeATP (E (max·α,ß-MeATP)) was the same as that of maximal vasoconstrictions for noradrenaline (E (max·NA)) in the internal carotid, pulmonary, mesenteric arteries, and aorta. Moreover, the value of (E (max·α,ß-MeATP)/E (max·KCl))/(E (max·NA)/E (max·KCl)) was 0.4 in each of the four arteries, but it was 0.8 in the tail artery. In conclusion, P2X(1) receptor-mediated vasoconstrictions are equally important in rat internal carotid, pulmonary, mesenteric arteries, and aorta, but much greater in the tail artery, suggesting its special role in physiological function.