Immunoreactive (ir)-transforming growth factor (TGF)-beta in rat corpus luteum: ir-TGF beta is expressed by luteal macrophages.

Western analyses and immunohistochemistry of transforming growth factor beta 1 (TGF beta 1) and TGF beta 2 were performed in rat luteal tissue at either the functional or regressing stage. Anti-TGF beta 1 or TGF beta 2 was localized simultaneously to macrophages within cultured luteal cells and frozen ovarian sections. By Western analysis, an active form of TGF beta (25 kDa) was detected clearly with anti-TGF beta 2 but only faintly with anti-TGF beta 1, and the former band from functional corpora lutea was more intense than that from regressing ones. Treatment with prolactin (PRL), a luteotropic hormone in rodents, also increased the intensity of 25 kDa TGF beta 2 in the corpus luteum. Several specific bands with higher molecular weights than 25 kDa were also recognized with anti-TGF beta 1 or TGF beta 2; they are probably ascribed to latent TGF beta s and/or TGF beta precursor proteins. In cultured luteal cells and frozen ovarian sections, many anti-TGF beta 1 or anti-TGF beta 2 positive cells from functional corpora lutea of pseudopregnant rats were double-stained with anti-macrophage. There were numerous macrophages in structurally regressing corpora lutea of pseudopregnant rats, but most of them were not stained with anti-TGF beta s. These results suggest that the expression of TGF beta, at least for TGF beta 2, is under the influence of PRL in the rat corpora lutea, and that macrophages are responsible for some, if not all, of the immunoreactive-TGF beta in rat luteal tissue.