Immunological relationships among ovine glycoprotein hormones

An antiserum to partially purified ovine FSH (but essentially free of LH) bound 125I-labelled ovine LH or bovine TSH. The antibody was directed exclusively against determinants in the alpha subunit. In a radioimmunoassay, only the intact ovine and bovine hormones and their alpha subunits were reactive; the hormone specific beta subunits exhibited no cross-reaction. The antibody directed against the alpha subunit was highly dependent on conformation. Human LH, FSH, TSH or their alpha subunits did not cross-react in the radioimmunoassay. Structural modifications such as acylation of the amino groups, reduction and alkylation of the S-S-bridges, or performic acid oxidation of the intact ovine FSH, LH or their alpha subunits virtually eliminated immunological reactivity. Using the alpha subunit radioimmunoassay, the presence of a significant quantity of free intact alpha subunit in standard (NIH) preparations of TSH-B7, FSH-S10 and LH-S19 was demonstrated.