Alpha 1-adrenoceptor-mediated responses in the vascular smooth muscle of spontaneously hypertensive rats.
The isometric tension development and 45Ca influx in response to norepinephrine (NE) and methoxamine stimulation were significantly (P less than 0.05) increased in spontaneously hypertensive rat (SHR) caudal arteries compared with Wistar-Kyoto (WKY) rats. However, there were no differences between WKY and SHR caudal artery rings, either in isometric tension or development of 45Ca influx in response to K+ depolarization. The Ca2+ sensitivity of NE- and methoxamine-stimulated arterial rings was significantly higher in the SHR caudal artery than in that of the WKY. Norepinephrine-stimulated contraction of both WKY and SHR caudal artery rings occurred mainly through activation of alpha 1-adrenoceptors. The number and affinity of alpha 1-adrenoceptors, estimated by 3H-prazosin binding, were comparable between WKY and SHR. It is concluded from these results that increased Ca2+ sensitivity to alpha 1-adrenoceptor stimulation in the SHR caudal artery rings appears to be caused by increased Ca2+ influx through receptor-operated Ca2+ channels.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D006973:Hypertension / Q000235:genetics* / Q000503:physiopathology; D007473:Ion Channels / Q000502:physiology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D051381:Rats; D011918:Rats, Inbred SHR / Q000502:physiology*; D011919:Rats, Inbred Strains / Q000502:physiology*; D011921:Rats, Inbred WKY; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*
D007473:Ion Channels; D011942:Receptors, Adrenergic, alpha; D002118:Calcium