Role of endothelium in dilator responses of spontaneously hypertensive rat arteries.

The possible role of endothelium in the vascular responses to vasodilator drugs was studied in relation to experimental hypertension. Short ring segments of the thoracic aorta and femoral artery were removed from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. They were rubbed on the intimal surface to destruct endothelial cells or unrubbed, and bathed in Krebs-bicarbonate solution for isometric recording of contractile and relaxant responses. The relaxant response to acetylcholine was abolished by rubbing all arteries tested. Rubbing also significantly attenuated the relaxation induced by adenosine in the SHR aorta and SHR and WKY femoral artery, and attenuated the relaxation by isoproterenol in the SHR femoral artery. In contrast, contractile response to norepinephrine was augmented by intimal surface rubbing in all arteries except the aorta of WKY. It is suggested that an endothelial compensatory mechanism develops to offset the diminished relaxant and/or increased contractile responsiveness of smooth muscle cells in the hypertensive rat arteries.