The objectives of this proposal are to determine the heterogeneous forms in which the gonadotropins, luteininzing hormone (LH) and follicle stimuating hormone (FSH) are secreted, circulated and are excreted. Methods used for characterization include chromatography, radioimmunoassay measurements of free gonadotropin subunits and fragments, comparison of in vitro biologic (B) and immunologic (I) concentration of gonadotropins, and rates or serum disappearance and renal clerance. In vitro bioassays have been developed for serum hLH, and validation of an assay for serum hFSH (using testosterone aromatization to estradiol in rat Sertoli cell cultures) is in progress. We propose to study mechanisms by which endogenously secreted and exogenously administered LHRH alters the B/T ratio and how gonadal steroids modulate these changes in the human and the rat. Perifused rat pituitary cells will be used to characterize newly secreted LH and FSH, and rat hepatocyte cultures to determine gonadotropin binding, metabolism and degradation. Besides advancing current knowledge regarding biologically active and inactive forms of gonadotropins, these studies are of potential benefit to patients. We have identified patients with normal or high levels of immunoreactive gonadotropins but immeasurable bioactive levels. In one group (alpha-secreting pituitary tumors) the discrepancy was traceable to immuno-crossreactivity of the biologically inert alpha subunit; in another, the LH molecule was abnormal (i.e., retained immunologic but lacked biological activity). Such patients are candidates for replacement therapy. Others exhibited biologic effects (precocious puberty) yet lacked measureable immuno- or bioactive gonadotropins. In such cases receptor avidity or target cell stimulation by other means is postulated. Conceivably, patients will be identified with normal bioactivity but abnormalities at the receptor level. Detailed characterization of the abnormal hormones will contribute to understanding of the clinical and physical determinants essential for biologic activity. Long-term benefits can be envisioned when regions responsible for biologic function are identified, synthesized and used as therapeutic agents, whereas analogs can be employed as contraceptive agents.
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