Immunoreactive and Bioactive Isoforms of Human Thyrotropin*

作者：Isabelle Sergi, Marie‐Jeanne Papandréou, GABRIELLA MEDRI, Colette Canonne, Bernard Verrier, Cathérine Ronin · 发表于：Endocrinology · 年份：1991 · DOI：10.1210/endo-128-6-3259 · 被引用次数：31 · 研究领域：Glycosylation and Glycoproteins Research、Monoclonal and Polyclonal Antibodies Research、Thyroid Disorders and Treatments

Isoforms of intrapituitary human TSH were separated by gel isoelectrofocusing, and their immunoreactivity analyzed by subsequent immunoblotting using polyclonal and monoclonal antibodies. Under these conditions, TSH polymorphism could be resolved as seven major isoforms (pI 8.6, 8.3, 8.0, 7.5, 7.0, 6.5, and 6.0) by both silver staining of the gels and binding to anti-TSH polyclonal antibodies. The distribution pattern of these forms appeared totally distinct from that of individual TSH alpha (pI 8.8, 8.4, 8.2, 7.6, 7.4, 6.8, 6.6, 5.8, and 5.4) and TSH beta (pI 8.7, 8.1, 7.2, 6.8, 6.2, and 5.8) subunits. While most anti-TSH polyclonal antibodies recognized neutral and alkaline isoforms of TSH (pI 8.6, 8.3, 8.0, 7.5, 7.0, 6.5, and 6.0) through beta determinants, they displayed a variable potency to bind acidic forms of the hormone (pI 5.8, 5.5, 4.8, and 4.5), in contrast to anti-TSH alpha antisera, which enlighted the broadest spectrum of isoforms. Monoclonal antibodies of various specificities largely reproduced this distribution, indicating that at least five distinct epitopes are coexpressed in the neutral and alkaline forms of TSH, but only two are expressed in the acidic ones. All of the forms were found to induce cAMP production and stimulate growth of FRTL-5 rat thyroid cells, although neutral forms proved to be definitely less potent than the others. We therefore, conclude that TSH isoforms differ in the expression of both their immunoreactive and bioactive domains and ...