Effect of hypertension on vascular contraction and sodium pump activity in rat cerebral basilar artery / 中国药理学通报

ABSTRACT

Aim To explore the effects of hypertension on the contractibility of rat basilar artery and its inter-actions with the sodium pump activity.Methods The basilar artery was respectively isolated from Wistar and SHR rats,and the isometric tension of arterial rings was measured by Multi Myograph System-610M.The cont-ractibilities of arterial rings induced by KCl or 5-HT were compared between the basilar arteries of the two groups of rats to analyze the effect of hypertension on the cerebral vascular tension and the activity of sodium pump.Results In SHR rats,the concentration-re-sponse curves of the contraction of isolated basilar ar-tery rings induced by KCl and 5-HT were significantly shifted to right,and the relaxation of vascular tone in-duced by K+which was reintroduced from the external was attenuated compared with those in the WR.These results suggested that hypertension could significantly decrease the activity of the sodium pump and the con-tractile responses of KCl and 5-HT.OUA could con-tract the basilar artery in a concentration-dependent manner,and its concentration-response curve was opti-mally fitted by a two-site binding modelKd was 1.7 ×10 -8 and 1.6 ×10 -5 mol·L-1,respectively.The results indicated that the two different function sodium pumps existed in the rat basilar arteryone with the high OUA affinity and the other with the low OUA af-finity.If the high and low affinity sodium pumps were inhibited by 5 ×10 -7 and 10 -4 mol · L-1 OUA,re-spectively,the concentration-response curves of KCl and 5-HT would shift to left in SHR rats but not in WR rats.It suggested that OUA could enhance the contrac-tion induced by KCl and 5-HT significantly,and a concentration-dependent effect was observed in the SHR vascular contraction induced by 5-HT (r =0.9393 ,P<0.05 ).When the two concentrations of OUA were applied,there was no significant difference in the shift left of the concentration-response curves in-duced by KCl in the SHR cerebral vessels.However, the marked difference was shown in the shift left in-duced by 5-HT.The results implied that only the high affinity sodium pump was involved in the contractile re-sponse of SHR cerebral vascular to KCl,whereas,the contractile response of SHR cerebral vascular to 5-HT was induced by both high and low affinity sodium pumps.Conclusion Hypertension could lower the contractile response of the basilar artery to vasocon-strictors,and the mechanism might relate to the de-creased sensitivity of the sodium pump induced by hy-pertension or the increased sensibility of the sodium pump to OUA.