THE EFFECTS OF GONADOTROPIN-RELEASING-HORMONE IMMUNIZATION AND RECOMBINANT FOLLICLE-STIMULATING-HORMONE ON THE LEYDIG-CELL AND MACROPHAGE POPULATIONS OF THE ADULT-RAT TESTIS

The objective of this study was to investigate the role of the gonadot ropins and, in particular follicle-stimulating hormone (FSH) in mainta ining the Leydig cell and macrophage populations of the adult rat test is. Adult male Sprague-Dawley mts received a gonadotropin-releasing ho rmone (GnRH) immunogen for a period of 12 weeks in order to induce a s elective deficiency in luteinizing hormone (LH) and FSH. Recombinant h uman FSH was then administered for 7, 14, and 21 days and macrophages and Leydig cells per testis quantified using the ''optical disector'' method. After GnRH immunization, Leydig cell and macrophage numbers we re reduced by 18% and 68%, respectively, compared with normal controls , resulting in an increase in the ratio of Leydig cells to macrophages from 4:1 to 9:1. Leydig cells regressed morphologically following GnR H immunization, and macrophage mean nuclear diameter was significantly reduced. Administration of FSH did not restore the numbers of either cell type; however, FSH did increase macrophage nuclear size. Eosinoph ils and mast cells were also found sparsely scattered throughout the i nterstitium after GnRH immunization and persisted in the FSH-treated a nimals. The results of this study indicate that in the adult rat: 1) b oth Leydig cell and macrophage numbers are reduced in the gonadotropin -deficient testis; 2) FSH has no effect on the number of either cell t ype in the absence of LH; and 3) testicular macrophage activity, as in dicated by nuclear size, is stimulated by FSH, either directly or indi rectly.