Pituitary control of proliferation and differentiation of Leydig cells and their putative precursors in immature hypophysectomized rat testis.

The objective of this study was to determine the effects of pituitary hormones (luteinizing hormone [LH], follicle-stimulating hormone [FSH], growth hormone [GH], and prolactin [PRL]) on interstitial cell proliferation and differentiation in the testis of immature hypophysectomized rats. Macrophages, Leydig cells, precursor mesenchymal cells, endothelial lymphatic cells, and myoid cells were studied. Our experimental approach was aimed at determining whether changes in a cellular subpopulation observed after pituitary hormone treatments were the result of division of existing cells in the population, of differentiation of interstitial precursor cells, or both. In this context, it must be stressed that our data reflected the effects of hormones to prevent the decline of cells due to hypophysectomy rather than their recovery. Macrophage proliferation was taken into account because macrophages closely resemble Leydig cells and are known to proliferate after hormonal treatment. A double-labeling procedure (acid phosphatase and anti-bromodeoxyuridine [anti-BUdR]) revealed that LH, FSH, and PRL increased the number of testicular macrophages 105-, 104-, and 103-fold, respectively, in hypophysectomized rats compared to hypophysectomized control animals. BUdR incorporation in testicular macrophages was greater after PRL treatment than after LH and FSH supplementation. In contrast, we were unable to demonstrate any effect of rat GH on the macrophage population. Light microscopic analysis of plastic embedded sections of treated rat testis revealed that LH increased the numbers of Leydig, precursor mesenchymal, and myoid cells 6-, 4-, and 1.3-fold, respectively. LH also stimulated BUdR incorporation into all interstitial cell types. PRL administration increased both the number of Leydig and precursor mesenchymal cells (each 3-fold) but decreased the number of endothelial lymphatic cells (1.5-fold) when compared to the control animals. In contrast, FSH did not increase the number and proliferation of Leydig cells but exerted a slight proliferative effect on the other interstitial cell populations. In GH-treated rats, the number of precursor mesenchymal cells increased two fold above the control rats. GH also exerted slight proliferative effects on both precursor mesenchymal and myoid cells. Immunohistochemical studies of steroidogenic enzymes in the testicular interstitium of treated rats demonstrated the presence of steroidogenic enzymes, not only in Leydig and precursor mesenchymal cells, but also in some (1%-2%) endothelial lymphatic cells and myoid cells. This may indicate that both of these cell types are also constitutively equipped to perform steroidogenesis or that they are precursor cells undergoing differentiation. Taken together, changes in the number of Leydig cells in our animal model appeared more likely to be dependent on the transformation of precursor cells than on division of preexisting mature Leydig cells.

20-alpha-Hydroxysteroid dehydrogenase from pseudopregnant rat ovary: obtention and characterization of a monoclonal antibody against the enzyme activity.

The enzyme 20-alpha-hydroxysteroid dehydrogenase (20-alpha-HSD) was purified from pseudopregnant rat ovaries and used as antigen for the development of a monoclonal antibody by the hybridoma technique. Spleen cells of BALB/c mice immunized with purified 20-alpha-HSD were fused with SP2/0 mouse myeloma cells. Among the colonies of hybrid cells, one (designated mAb-HSD 11) was found to be secreting antibodies (IgM) able to inhibit 20-alpha-HSD activity. The antibody-secreting hybridome was amplified by ascitic fluid production and the monoclonal antibody purified by Bakerbond ABx procedure. Purified mAb-HSD 11 was able to inhibit 20-alpha-HSD activity in a dose-dependent manner. Studies of Michaelis constants of 20-alpha-HSD indicate that this monoclonal antibody increases the Km for 20-alpha-dihydroprogesterone and decreases the Vmax.

Expression of 20 alpha-hydroxysteroid dehydrogenase in nonlymphoid hemopoietic cell lines.

Expression of 20 alpha-hydroxysteroid dehydrogenase (20 alpha-SDH), a putative T cell marker, has been examined in a number of nonlymphoid hemopoietic cell lines. Both promyelocytic and stromal bone marrow lines expressed significant 20 alpha-SDH activity which was not correlated with virus infection or growth rate. 20 alpha-SDH therefore is not a unique marker for T cells in hemopoietic tissues. This result is discussed in relationship to the action of the newly proposed interleukin 3.