IMMUNOHISTOCHEMICAL LOCALIZATION OF TRANSFORMING GROWTH FACTOR-BETA-1 AND FACTOR-BETA-2 DURING FOLLICULAR DEVELOPMENT IN THE ADULT-RAT OVARY

The transforming growth factors-beta (TGF-beta) affect the metabolic activities of each of the cell types in the ovary. In vitro studies using immature rat ovaries have shown the expression of TGF-beta(1) and/or TGF-beta(2) mRNA in thecal/interstitial cells and in granulosa cells (Mulheron and Schomberg, 1990; Mulheron et al., 1991). To obtain information on the localization of TGF-beta(1) and TGF-beta(2) in the rat ovary in vivo, we have examined the immunohistochemical staining using antibodies specific for either TGF-beta(1) or TGF-beta(2). In the adult ovary the immunostaining for TGF-beta(1) was intense, whereas the staining for TGF-beta(2) was faint. The pattern of immunostaining for TGF-beta(1) and TGF-beta(2) remained constant in the interstitial cell compartment and was not affected by the stage of the oestrous cycle. Since the interstitium surrounds follicles at all stages of development we conclude that TGF-beta is not actively involved in regulating the progression of follicles at discrete stages. At the time of antrum formation in the follicle, intense staining for TGF-beta(1) was observed in thecal cells. Around the preovulatory stage of development, TGF-beta(1) and TGF-beta(2) immunoreactivity was also found in the granulosa cells. In the corpus luteum, intense staining for TGF-beta(1) was found in some areas, whereas other areas were negative. Weak to moderate staining for TGF-beta(2) was observed. In conclusion, all major cell types show strong immunostaining for TGF-beta(1) and less intense staining for TGF-beta(2), confirming an autocrine/paracrine role for TGF-beta-s in the regulation of ovarian cell growth and function.