Autoradiographical localization of luteinizing hormone releasing hormone (LHRH) receptors on rat testicular intertubular cells fractionated on percoll density gradients

The specific binding of ¹²⁵I-1abelled [D-Ser(tBu)⁶des-GlyNH¹⁰₂] LHRH ethylamide (LHRH-A) to testicular intertubular cells fractionated on Percoll density gradients was investigated. The greatest binding per cell occurred in the density region which contained the largest proportion of Leydig cells (sp. gr.1·0820–1·0585). Autoradiographs of the cells from this region confirmed that silver stains were predominantly located over the Leydig cell, significantly (P < 0·01) more grains were observed over this cell type in the total binding fractions than in the non-specific binding fractions. However, 5·9% of cells other than Leydig cells (testicular macrophages and indeterminate connective tissue cells) from this region also displayed significant disp1aceable binding (P < 0·01). The location of [¹²⁵I]LHRH-A binding to cells in other density regions, which did not contain identifiable Leydig cells, could not be established by autoradiography. These results confirm that the Leydig cell possesses LHRH receptors, but also indicate that other testicular cells have specific, highaffinity binding sites for LHRH-A, and may either be responsive to direct stimulation by LHRH, or may partially mediate the effects of LHRH and its agonists on Leydig cell function.