Radioimmunoassay of bencyclane in human serum

A radioimmunoassay of bencyclane in human serum was developed. Male rabbits were immunized with p-(3-carboxy-propoxy)bencyclane-bovine serum albumin conjugate, giving antisera with high titers. 125I-p-Hydroxybencyclane with a high specific activity was prepared as a labelled antigen by a chloramine-T method. In the radioimmunoassay procedure, a mixture of serum sample, diluted antiserum and 125I-antigen solution were incubated at 4 degrees C for 18 h, and bound-free separation was carried out by a dextran-coated charcoal method. The detection limit of bencyclane in human serum was 1.0 ng/ml, and the cross-reactivity of the antiserum with metabolites was found to be very low. Serum samples from healthy volunteers dosed orally with bencyclane fumarate were analyzed by both of the radioimmunoassay and gas chromatography-mass spectrometric methods. An excellent correlation was observed between the values obtained by both methods.