Influence of OSW-1 [3 beta,16 beta,17 alpha-trihydroxycholest-5-en-22-one 16-O-(2-O-4-methoxybenzoyl-beta-D-xylopyranosyl)-(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 measured isometrically to study the influence of OSW-1 [3 beta,16 beta,17 alpha-trihydroxycholest-5-en-22-one 16-O-(2-O-4-methoxybenzoyl-beta-D-xylopyranosyl)-(1 right arrow 3)-(2-O-acetyl-alpha-L-arabinopyranoside)], a steroidal saponin, on the endothelium dependent and independent relaxation caused by acetylcholin (ACh) and sodium nitroprusside (SNP), respectively. OSW-1 (10(-7) M), which has more than 100 times higher concentration for anti-tumor activity, had no influence on either the endothelium dependent or independent relaxation. OSW-1 (10(-6) M, 0.9 microgram/ml) slightly reduced the endothelium dependent relaxation caused by ACh but did not affect the SNP-induced relaxation. In contrast to OSW-1, 1 mg/ml of saponin significantly suppressed the ACh-induced relaxation and shifted 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 though the higher concentration of OSW-1 shows weaker influence on the endothelium function compared with saponin, OSW-1 at an anti-tumor dose has no influence on either endothelium or smooth muscle function.