Purification of cardiotonic steroids from preeclamptic placentae. (a) Levels of MBG and endogenous ouabain in control (Ctrl) and preeclamptic placentae. *P < 0.001 vs. Ctrl. (b–d) Pattern of elution of MBG-immunoreactivity and ouabain-immunoreactivity following HPLC fractionation of placental extracts on Zorbax Eclipse XDB-C18 HPLC. (e,f) Elution of ouabain (1 μmol/l; 50 μl) and MBG (1 μmol/l; 50 μl) standards from Zorbax Eclipse XDB-C18 HPLC. CTS, cardiotonic steroids; EO, endogenous ouabain; HPLC, high performance liquid chromatography; mAb, monoclonal anti-marinobufagenin antibody; MBG, marinobufagenin; PE, preeclampsia.