Specific Binding of ¹²⁵I-Labeled Human Follicle Stimulating Hormone to Testicular Slice

Abstract

A simple radioreceptor-assay technique for human follicle stimulating hormone (hFSH) with use of rat testicular slice and enzymatically ¹²⁵I-labeled hFSH was described. It was shown that 125I-hFSH bound to the testicular slice (30mg) was approximately 2% of the total amount added to the tube (2ng/tube), half of which was displaceable in the presence of 1μg/tube of unlabeled hFSH. Although only small amount of ¹²⁵I-hFSH was bound specifically to the tissue, the binding was not inhibited by other peptide hormones tested. The testicular receptor for hFSH had high affinity constant (2.5×10⁹M^-1) and hormonal specificity, suggesting a possibility of the physiological application of this radioreceptor assay for the measurement of hFSH in body fluids.