Localization of alpha-inhibin-31 in rodent testis and brain by immunocytochemical procedure and Western blot analysis.

Using an anti-serum against synthetic alpha-inhibin-31, we have studied its cellular locations in rodent testis and brain. Western blot analysis detected several molecular forms of the protein(s). A protein of 17 KDa in size was detected in testis of one month old mice. Two major bands of molecular weights 39 kDA and 21 kDA were detected in mature mouse testis. The 39 kDA protein was also present in male brain, female brain and ovary. No protein similar in size to alpha-inhibin-31 was detected with this antiserum, suggesting that the antibody recognized only the precursor of the alpha-IB-31 molecule. Immunocytochemical studies revealed that these molecules were located in the cytoplasm of the interstitial Leydig cells. The immunocytochemical reaction can be eliminated by pre-incubation with synthetic alpha-inhibin-31. Immunoreactive substances were also demonstrated at the blood-brain barrier on the external surface of the ependymal cells in the third ventricle of the rat brain. In the pituitary, similar pattern of localization was also observed in the cuboidal-columnar epithelial cells that lined the par tuberalis between the anterior and intermediate lobes. The immunoreaction to the neural cells cannot be completely abolished by competition with the synthetic peptide. These observations suggested that alpha-inhibins are located in the Leydig cells of the testis as well as in the brain, pituitary and ovary.