Distribution of immunoreactive 2',5'-oligoadenylate synthetase in mouse reproductive organs

Although 2', 5'-oligoadenylate synthetase (2-5AS) is an enzyme induced by inferferon (IFN) or viral infections and mediates one of the principal antiviral pathways turned on by IFN, low constitutive levels of the enzyme can be detected in various "normal" animals that have not been treated with IFN or virus. The distribution of this enzyme in the female and male reproductive organs of normal healthy mice was studied by Western blotting and by an immunohistochemical method, using a specific monoclonal antibody. On Western blotting, an antibody to 42-kD 2-5AS reacted with extracts from the ovary, oviduct, uterus, vagina, and placenta among the female reproductive organs, and testis, epididymis, and ductus deferens in the male. Immunohistochemically, the 2-5AS was localized on the following cells in the female reproductive organs: oocytes in the ovary; epithelium in the oviduct, uterus, and vagina; and trophoblasts in the placenta. Furthermore, the 2-5AS was localized on the epithelium and muscular layer in the ductus deferens and epithelium in the penis of the male mice, whereas the epithelium of the testis, epididymis, and seminal vesicle were stained faintly. It is well known that IFN is produced continuously in normal mice, so the 2-5AS in the tissues of normal mice is considered to be induced by such IFN produced under physiological conditions. Expression of the 2-5AS on the epithelium and trophoblasts in the reproductive organs may be responsible for the prevention of viral infections. However, the enzyme in oocytes may have some functions other than as an antiviral agent, since the enzyme was not detectable in embryos during early development.