Chemical removal of the endothelium by saponin in the isolated dog femoral artery.

Chemical removal of the endothelium by saponin in the isolated dog femoral artery was investigated by comparing the relaxant responses to endothelium-dependent and -independent vasodilators of saponin-treated rings with the responses of non-treated rings. Saponin treatment was done by incubating rings with Krebs-Henseleit solution containing 0.1, 0.3 or 1 mg/ml of saponin for 45 min at 37 degrees C. In non-treated rings, acetylcholine (10(-8)-3 X 10(-6) M) caused a concentration-dependent relaxation of rings precontracted with prostaglandin F2 alpha (3 X 10(-6) M). The acetylcholine-induced relaxation was reduced in rings pretreated with 0.1 mg/ml of saponin and almost abolished with 0.3 or 1 mg/ml. Prostaglandin F2 alpha-induced contraction was suppressed weakly by treatment with 0.3 mg/ml and markedly with 1 mg/ml saponin. The treatment with 0.3 mg/ml saponin markedly reduced relaxations caused by substance P (10(-9)-3 X 10(-8) M) and by Ca2+-ionophore A23187 (10(-6) M). Relaxant responses of saponin-treated rings to nitroglycerin and to nitroprusside were almost identical with those of non-treated rings. These results showing selective suppression by saponin of the endothelium-dependent relaxation suggest that saponin removes the endothelial cells from the intimal surface of the artery, and this was confirmed by electron microscopy. The endothelium removing method with saponin seems to be useful as a pharmacological tool for vascular investigations.