|Budget Amount *help
¥4,000,000 (Direct Cost: ¥4,000,000)
Fiscal Year 1999: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1998: ¥2,500,000 (Direct Cost: ¥2,500,000)
Ontogenetical changes of horse testis were examined morphologically, histochemically, immunohistochemically, ultractructurally and molecular biologically with special reference to expression of inhibin α-, βA-, βB-subunits.
Spermatogenesis initiated in the spring of 2 years old, and spermatogeneic activity appeared to inverase with age up to 9 years old. The most characteristic feature during development of horse testis is the appearance and disappearance of pigmented cells. These cells first appeared in 3-day old colt and gradually increased in volume up to 1 year old. The number of cells reached maximum at 2 months old, graduelly decreased, and completely disappered after 3 years old. According to their histochemical and ultrastructural feature, the pigmented cells might be macrophages phagocytized fetal types of Leydig cells.
Immunohistochemically, inhibin α-, βA- and βB-subunits were found not only in Lydig cells but also in Sertoli cells, respectively. But their intensities of posit
ive stainings were more intense in Lydig cells than in Sertoli cells.
For in-situ hybrldization, digoxigenin-labelled comprementary RNA probes were prepared to detect intracellular messenger RNAS of inhibinα-, βA- and βB-subunits. Signals for inhibin α-, βA- and βB-subunits were detected in Leydig cells and the basal region of seminiferous epithelium. Although exact localization of the signals were could not identified in the basal region of the seminiferous tubules due to the limitation of this method, it may well be that Sertoli cells have the highest possibility. However we could not excluded the spermatogonia. During prenatal and postnatal stages and even in adult horses, these seults are fundamentally similar. The present results suggested that inhibin α-subunit and inhibin/activin βA- and βB-subunits were expressed not only in Sertoli cells but also in Lydig cells, and the expression level was higer in Leydig cells than in Sertoli cells. Furthermore this study suggested that Leydig cells are the major source of inhibin and/or activin in horse testis. Inhibin and/or activin may play reguration role of testicular function by autocrine and/or paracrine manner, but they are not known in detail. Less