The relaxing effect of Kouzilan on isolated thoracic aortic ring of SD rat / 中国病理生理杂志

ABSTRACT

Kouzilan was selected as a potent hypotensive drug, and two fractions, K01 (hydrosoluble element) and K02 (fat-soluble element), were extracted from it. Thepresent study focused on its mechanism of vascular effects in vitro. The data showed thatK01 and K02 antagonized the contraction of isolated thoracic aortic ring of SD rat, indu-ced by norepinephrine (NE, 1 ?mol/L). The IC_(50) values of K01 and K02 were 1.98g/Land 1.15g/L respectively, and that of Verapamil (Ver) was 0.88 ?mol/L. K01, K02 andVer all shifted the dose-response curves of NE to the right in a noncompetitive antagonis-tic manner, and they also depressed the maximal efficacy of contraction. Added NE intoa calcium-free K-H solution to induce aortic vessel contraction (phase 1), then added cal-cium (2.5mmol/L) to induce continued contraction (phase 2), K01 depressed phase 2significantly. In lower concentration, K02 was similar to K01, however, in higher concen-tration, it depressed phase 1 and phase. 2 significantly, which was similar to Ver. Theseresults suggested that K01 and K02 had a vasodilative effect, which was related to theblockade of the receptor operated calcium channel (ROC). K02 inhibited both the calciumrelease from intracellar storage sites and the influx of extracellar calcium, but K01 onlyinhibited the latter.