The Development of a Radioimmunoassay for Oxytocin: Radio-Iodination, Antibody Production and Separation Techniques

Abstract

A simple and rapid method is described for labelling oxytocin with 131I at a high specific activity. This method is compared with those of previous workers. A satisfactory antiserum has been raised by direct intra-lymph node injection of oxytocin adsorbed to carbon microparticles. A number of methods for separating antibody-bound from free oxytocin are described, and reasons given for preferring a procedure using ammonium sulphate precipitation. These data form the basis for developing a radioimmunoassay intended for the determination of oxytocin in human plasma.

The Development of a Radioimmunoassay for Oxytocin: Sensitivity of the Assay in Aqueous Buffer Solution, Specificity and the Dissociation of Immunological and Biological Activity

“…In so far as it is possible to make any interpretation, the results would suggest that the antibodies to both oxytocin and vasopressin are directed to the C-terminal end of the molecule. This would agree with previous findings (Chard et al 1970) that iodine substitution of the tyrosine residue of oxytocin appears to have little effect on its immunoreactivity.…”

“…of the peptide. The diluent buffer used, the method of radio¬ iodination, the preparation of antisera, and the techniques for separating antibodybound from free hormone have been described previously (Chard et al 1970). …”

“…By contrast, a radioimmunoassay for this hormone should yield similar sensitivity, but with fewer problems of interference by non¬ specific factors. The preparation of antiserum to oxytocin, a simple method for labelling the peptide with 131I, and techniques for separating antibody-bound from free oxytocin have been described previously (Chard, Kitau & Landon, 1970). We have reported, in a preliminary communication, an assay using these materials (Chard, Forsling & Kitau, 1969).…”

Development of a Radioimmunoassay for Cyclic Somatostatin: Antibody Production, Comparative Radioiodination, and Dose-Response Curve

“…5). This effect has already been utilized for the purification of labeled ocytocin and vasopressin (19,16). Strong adsorption of iodinated somatostatin to a solid phase can also be demonstrated with other Chromatographie techniques, e. g. CMC-ion^exchange (10) and cellulose acetate foil electrophoresis (18).…”

Immunochemical and Enzymatic Studies on the Soluble Antigens of Normal Human Kidney

“…New Zealand white rabbits weighing about 5 kg were immunized according to the method described by C hard et al [27], Antigenic solution containing 20 mg of proteins dissolved in 0.5 ml of PBS and emulsified with an equal volume of Freund's complete adjuvant were injected into the popliteal lymph nodes. Four weeks later, each rabbit received two 10-mg protein injections, one subcutaneously and the other intramuscularly.…”