17β-Estradiol inhibits calcium-dependent and -independent contractions in isolated human saphenous vein

In Ca2+-free hyperpolarizing solution, pretreatment with E2, concentration dependently reduced contractions induced by cumulative addition of calcium chloride. Furthermore, E2 elicited relaxant effects on the PGF2α-induced contractions in Ca2+-free solution in the presence or absence of CPA. Both E2 and NIF produced significant relaxation in HSV rings contracted by direct activation of PKC in Krebs' solution. However, in Ca2+-free solution, NIF failed to induce relaxant effect but E2 kept its effect on the PDBu-induced contraction. These results suggest that the relaxant effect of E2 on HSV is elicited by calcium-dependent and -independent pathways. The calcium-independent pathway may involve PKC inhibition.