Testis-Like Steroidogenesis in the Ovotestis of the European Mole, Talpa europaea(2)

16 Apr

The ovarian portion of the ovotestis contains morphologically normal follicles, while the adjacent testicular portion, or interstitial gland, consists primarily of well-differentiated Leydig cells with varying numbers of seminiferous tubules. Unlike what is seen in the normal testis, the interstitial gland is devoid of germ cells: all of the germ cells are confined to the ovarian portion of the ovotestis. Early studies describe differentiation of the ovarian and interstitial gland portions of the ovotestis as occurring during fetal development (reviewed in ). Females possess a normal vagina, uterus, and oviducts. However, adjacent to the interstitial gland are abnormally developed epididymides, suggesting that the ovotestis secretes testosterone during fetal development. The clitoris is similarly masculinized and develops in the fetus in a remarkably similar fashion to the penis of the male (Fig. 1). Studies in T. occidentalis suggested that plasma testosterone might vary seasonally, but high variability in the data precluded any such conclusions. buy ventolin inhalers

The objective of this study was to examine further the hypothesis that the interstitial gland portion of the ovotestis is the primary source of plasma testosterone in the mole T. europaea and to assess the seasonal functionality of these tissues. RIA and in vitro incubation of gonadal tissues were used to examine the capacity of the interstitial gland from adult females to synthesize testosterone and to determine whether testosterone levels vary seasonally, reflecting the change in size of the interstitial gland. In addition, studies of female spotted hyenas, another species with masculinized genitalia, had revealed substantial circulating levels of androstenedione, primarily of ovarian origin, throughout life, and exceptional elevation of testosterone concentrations during pregnancy. The latter was found to result from placental conversion of androstenedione to testosterone and was tentatively linked with genital masculin-ization of the developing fetus. We accordingly assessed plasma androstenedione concentrations in female moles in order to determine whether a similar tendency toward generally elevated androstenedione levels, or pregnancy-elevated testosterone levels, are associated with mas-culinization of the genitalia in Talpa.