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Peritubular myoid cells from immature rat testes secrete activin-A and express activin receptor type II in vitro
J P de Winter1, H M Vanderstichele, G Verhoeven
1Department of Endocrinology and Reproduction, Medical Faculty, Erasmus University, Rotterdam, The Netherlands.
Abstract:
The expression of activin type II and IIB receptors and inhibin alpha-, beta A-, and beta B-subunit messenger RNAs (mRNAs), and the secretion of immunoreactive and bioactive activin during culture of testicular peritubular myoid cells and peritubular myoid cell lines were studied. Cultured peritubular myoid cells and cell lines expressed high levels of inhibin beta A-subunit mRNA and some inhibin alpha- and beta B-subunit mRNA. Activin receptor type II mRNA was also detected, whereas activin receptor type IIB mRNA expression was not found. Expression of the beta A-subunit mRNA was present immediately after isolation of the cells and increased during culture in Eagle's Minimum Essential Medium containing 10% fetal calf serum. beta A-Subunit mRNA expression was not regulated by the synthetic androgen R1881. Western blotting of peritubular myoid cell- and peritubular cell line-conditioned media with a polyclonal antiserum against recombinant activin-A revealed the presence of 25-kilodalton activin-A, whereas activin bioactivity was detected using the animal cap assay. Because of the secretion of activin-A by peritubular myoid cells, the effects of recombinant activin-A on Sertoli cell inhibin and transferrin secretion were examined. Activin-A stimulated both basal and FSH-stimulated inhibin and transferrin production by Sertoli cells after 72 h of culture. These effects resemble the effects of the testicular paracrine factor PmodS on Sertoli cell function. It is concluded that activin-A is secreted by peritubular cells in vitro and that activin-A shares a number of effects on Sertoli cell function with PmodS.
Insights
Testicular peritubular myoid cells secrete activin-A, which influences Sertoli cell function. This activin-A stimulation of inhibin and transferrin production mimics the effects of the paracrine factor PmodS.
Area of Science:
- Reproductive biology
- Endocrinology
- Cell biology
Background:
- Testicular peritubular myoid cells play a crucial role in regulating testicular function.
- Activins and inhibins are key regulators of the hypothalamic-pituitary-gonadal axis.
- Understanding paracrine signaling within the testis is essential for reproductive health.
Purpose of the Study:
- To investigate the expression of activin receptors and subunits in testicular peritubular myoid cells.
- To determine if peritubular myoid cells secrete activin.
- To examine the effects of secreted activin-A on Sertoli cell function.
Main Methods:
- Studied messenger RNA (mRNA) expression of activin receptors and inhibin subunits in cultured peritubular myoid cells and cell lines.
- Analyzed conditioned media from these cells for secreted activin using Western blotting and bioactivity assays.
- Assessed the impact of recombinant activin-A on Sertoli cell inhibin and transferrin secretion in vitro.
Main Results:
- Peritubular myoid cells and cell lines expressed inhibin beta A-subunit mRNA and activin receptor type II mRNA, but not activin receptor type IIB.
- Activin-A was detected in conditioned media, indicating secretion by peritubular myoid cells.
- Activin-A stimulated both basal and FSH-stimulated inhibin and transferrin production by Sertoli cells.
Conclusions:
- Activin-A is secreted by testicular peritubular myoid cells in vitro.
- Secreted activin-A modulates Sertoli cell function, specifically influencing inhibin and transferrin secretion.
- The observed effects of activin-A on Sertoli cells are similar to those of the testicular paracrine factor PmodS.