LEUKOCYTE POPULATIONS OF THE ADULT-RAT TESTIS FOLLOWING REMOVAL OF THE LEYDIG-CELLS BY TREATMENT WITH ETHANE DIMETHANE, SULFONATE AND SUBCUTANEOUS TESTOSTERONE IMPLANTS

The influence of the Leydig cells on the leukocyte population of the t estis was investigated. Leydig cells were destroyed by ethane dimethan e sulfonate (EDS) treatment in adult male rats, with or without low-do se s.c. testosterone implants to prevent Leydig cell recovery. Leukocy tes were counted in perfusion-fixed frozen testis sections, by use of cell-specific monoclonal antibodies (mAbs) with immunoperoxidase detec tion, or toluidine blue staining. The majority (81%) of testicular leu kocytes (OX1(+)) were immunopositive for the resident macrophage-speci fic mAb, ED2, and/or the monocyte/macrophage/dendritic cell mAb, ED1. The remaining leukocytes were principally T lymphocytes (R73(+)). B ly mphocytes (OX33(+)) and metachromatic mast cells were not observed in the normal testis. Treatment with EDS caused a transient increase in E D1(+), ED2(+), and R73(+) cell numbers in the testis, although other e vidence of an inflammatory reaction, such as increases in major histoc ompatibility complex class II antigen, interleukin-2 receptor expressi on, or capillary permeability, were not observed. At 21 days after EDS treatment, there was a significant decline in macrophage numbers (to approximately 50% of control testis), and T lymphocytes returned to pr etreatment levels. After Leydig cell recovery (41 days after treatment ), macrophages also returned to pretreatment levels in EDS-treated rat s, but remained reduced in EDS-treated animals with testosterone impla nts. In addition, EDS treatment stimulated a progressive increase in i ntertubular mast cells, which was significantly inhibited in the testo sterone-implanted rats. The data indicate that numbers of testicular m acrophages and mast cells, but not of lymphocytes, within the adult ra t testis are directly or indirectly regulated by the Leydig cells.