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This Article Full Text Full Text (PDF) All Versions of this Article: 68/5/1918    most recent biolreprod.102.012856v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Kaneko, H. Articles by Hasegawa, Y. Search for Related Content PubMed PubMed Citation Articles by Kaneko, H. Articles by Hasegawa, Y. Agricola Articles by Kaneko, H. Articles by Hasegawa, Y.

Molecular Weight Forms of Inhibin A and Inhibin B in the Bovine Testis Change with Age¹

Genetic Diversity Department,³ National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602, Japan Laboratory Animal Science,⁴ School of Veterinary Medicine and Animal Science, Kitasato University, Towada, Aomori 034-8628, Japan

To investigate alterations in the molecular weight forms of inhibin in bull testis from the infantile (4–5 wk of age) to postpubertal (49–56 wk of age) periods, testicular homogenates were obtained from animals of various ages and fractionated by a combination of immunoaffinity chromatography and SDS-PAGE. Subsequently, the fractions eluted from the SDS gels were assayed for total inhibin, inhibin A, and inhibin B by fluoroimmunoassay or immunofluorometric assays (IFMAs) and for inhibin bioactivity by an in vitro bioassay. The molecular mass patterns of inhibin A and inhibin B in the testis, as determined by the dimer-specific IFMAs, showed the presence of a peak of approximate 47 kDa until 21–26 wk of age. However, the peak disappeared after 31–32 wk of age. As bulls aged, especially after 31–32 wk of age, inhibin A and inhibin B levels increased in the molecular mass region of 27–34 kDa. Total inhibin showed two peaks, of between 20 and 26 kDa and at approximately 47 kDa, until 21–26 wk of age and a single peak between 20 and 30 kDa after 31–32 wk of age. The eluted fractions corresponding to 29, 31, or 47 kDa gave a dose-response curve that was parallel to the curve generated with 32-kDa inhibin A or 29-kDa inhibin B standard in the IFMA for inhibin A or inhibin B. The fractions corresponding to 29 and 31 kDa suppressed basal release of FSH from rat pituitary cells, but the 47-kDa fraction had a lower FSH-suppressing activity. In the testes of older bulls, immunoblot analysis revealed the presence of a 29-kDa band cross-reacting with inhibin and inhibin ß_B antibodies and of a 31-kDa band cross-reacting with inhibin and inhibin ß_A antibodies. The 47-kDa band was recognized by the , ß_A, and ß_B antibodies. Immunohistochemisty of the testis at each age showed that inhibin subunits were found exclusively in Sertoli cells, but the intensity of immunostaining diminished in older bulls, in parallel with the decrease in the testicular concentrations of total inhibin. We conclude that 1) bovine Sertoli cells produce both inhibin A and inhibin B, 2) inhibin production in Sertoli cells during the prepubertal period is characterized by the 47 kDa inhibin-related material that contains precursor forms of inhibin A and inhibin B, and 3) the proportion of the mature forms of inhibin A and inhibin B increases as bulls age, although total inhibin production in Setroli cells decreases.

¹ This work was supported by the Ministry of Agriculture, Forestry and Fisheries, Japan.

² Correspondence: Hiroyuki Kaneko, Genetic Diversity Department, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki 305-8602, Japan. FAX: 81 298 38 7408; kaneko{at}nias.affrc.go.jp