INFLUENCE OF OSW-1 ETA,16-BETA,17-ALPHA-TRIHYDROXYCHOLEST-5-EN-22-ONEL)-(1-]3)-(2-O-ACETYL-ALPHA-L-ARABINOPYRANOSIDE)], A STEROIDAL SAPONIN, ON ENDOTHELIUM-DEPENDENT RELAXATION CAUSED BY ACETYLCHOLINE IN RAT AORTA

The tension of isolated ring preparation of the aorta from rats was me asured isometrically- to study the influence of OSW-1 [3 beta,16 beta, 17 alpha-trihydroxycholest-5-en-22-one methoxybenzoyl-beta-D-xylopyran osyl)-(1-->3)-(2-O- acetyl-alpha-L-arabinopyranoside)], a steroidal sa ponin, on the endothelium dependent and independent relaxation caused by acetylcholin (ACh) and sodium nitroprusside (SNP), respectively. OS W-1 (10(-7) M), which has more than 100 times higher concentration for anti-tumor activity, had no influence on either the endothelium depen dent or independent relaxation. OSW-1 (10(-6) M, 0.9 mu g/ml) slightly reduced the endothelium dependent relaxation caused by ACh but did no t affect the SNP-induced relaxation. In contrast to OSW-1, 1 mg/ml of saponin significantly suppressed the ACh-induced relaxation and shifte d the dose-relaxation curve for SNP to the right, OSW-1 (10(-7) and 10 (-6) M) did not affect the norepinephrine-induced contraction but 1 mg /ml of saponin significantly attenuated it, The results suggest that t hough the higher concentration of OSW-1 shows weaker influence on the endothelium function compared with saponin, OSW-1 at an anti-tumor dos e has no influence on either endothelium or smooth muscle function.