Effects of blockers of Ca2+ channels and other ion channels on in vitro excystment of Paragonimus ohirai metacercariae induced by sodium cholate.

The inhibitory effects of various ion channel blockers were examined on in vitro excystment of Paragonimus ohirai metacercariae induced by a bile salt, sodium cholate. At a concentration of 10 microM, bepridil, a non-selective Ca(2+) channel blocker, completely inhibited in vitro excystment, whereas TEA, lidocaine, and R(+)-IAA-94, channel blockers against K(+), Na(+) and Cl(-) ions, respectively, benzamil, an Na(+)/H(+) and Na(+)/Ca(2+) ion exchanger blocker, and R(+)-DIOA, a [K(+), Cl(-)] cotransporter inhibitor, did not. Considering the previous result that Ca(2+) ionophores are also efficient inducing factors for in vitro excystment of P. ohirai metacercariae and the present result, bile salts appear to induce the excystment of P. ohirai metacercariae through evoking the Ca(2+) channels of target cells within the metacercarial juveniles.