Activins are members of the transforming growth factor-b superfamily and are homodimeric proteins composed of two inhibin/activin b-subunits linked by a disulfide bridge. Activin was originally identified as a stimulator of FSH (follicle-stimulating hormone) secretion. [6][7][8] Later, activins were shown to be expressed in various organs during development and in acquired conditions, and to have a wide variety of biological functions, including regulation of cell proliferation and differentiation, and induction of mesodermal tissues during amphibian development. 12,13) Recent studies have shown that activin A plays several roles in rat liver in vivo and in vitro. [13][14][15][16][17] It inhibits mitogeninduced DNA synthesis in vitro, 14) induces hepatocellular apoptosis in vivo and vitro, [15][16][17] and stimulates glycogenolysis in vitro.18) Activin C has been reported to have no effect on DNA synthesis by liver tumor cell line HepG2.11) However, there have been no reports on the actions of activin AB and B in rat liver either in vivo or in vitro. It, therefore, seemed meaningful to examine the effect of activins AB and B on the liver functions that have been shown to be regulated by activin A. In this regard, we were especially interested in mitogen-stimulated DNA synthesis as a model system for its biological significance, because expression of b A and b B mRNA in rat liver has been found to change markedly in rat models of liver regeneration. 14,19) In this paper, we examined the effect of activins AB and B on DNA synthesis stimulated by epidermal growth factor (EGF) in primary cultured rat hepatocytes and compared their effect with that of activin A. MATERIALS AND METHODS MaterialsThe materials used for cell isolation and cell culture were the same as reported by Tanaka et al. 20) Recombinant human (rh) activin A was kindly provided by Dr. Y. Eto (Ajinomoto Co., Inc., Japan). Porcine activin A, activin AB, and activin B were purchased from Wako (Osaka, Japan). EGF was obtained from Toyobo (Osaka). [3 H]thymidine (89.9 Ci/mmol) was purchased from NEN Life Science Products (Boston, MA, U.S.A.).Cell Isolation and Monolayer Culture Parenchymal hepatocytes were isolated from adult male Wistar strain rats weighing 180-200 g by in situ perfusion of the liver with collagenase, 20) and they were suspended, 2ϫ10 5 cells/ml, in Williams' E medium containing 5% fetal bovine serum, 10 nM insulin, and 1 nM dexamethasone, and cultured at 0.2ϫ10 5 cells/cm 2 in a 48-well and 6-well microplate (IWAKI) precoated with collagen type-1 AC in a humidified chamber at 37°C under 5% CO 2 and 30% O 2 in air. Cells plated in the 48-well and 6-well plate were used to measure DNA synthesis and [ 125 I]rh activin A binding, respectively. After 2.5 h, the medium was replaced with serum-and hormone-free medium containing aprotinin (1 mg/ml). Measurement of [ 3 H]thymidine IncorporationAfter 15 h, the medium was replaced with hormone-free medium containing aprotinin (1 mg/ml) and 0.1% bovine serum albumin (BSA), and various hormones we...

Mature cystic teratoma (MCT) is rarely involved in the overproduction of steroid hormones in contrast to sex cord stromal tumors. A 31-year-old woman visited our hospital with hirsutism, hoarseness, and hair loss from the scalp. Serum testosterone and free-testosterone levels were 7.3 ng/ml and 2.3 pg/ml, respectively, which were markedly in excess of the age adjusted female standard levels. Basal blood levels of steroid hormones and serum levels of 17-hydroxyprogesterone at 1 h after intravenous injection of adrenocorticotropic hormone demonstrated that 21-hydroxylase deficiency was not the underlying cause of her virilization. A subsequent chromosomal test with G-banding revealed a karyotype of 46XX. Magnetic resonance imaging revealed a mass in the left ovary, which was subsequently diagnosed as MCT. Detailed pathological analysis of the tumor indicated that it was comprised of skin components, sweat glands, with hair and fat texture, glandular epithelium and fibrous connective tissue, consistent with the characteristic composition of MCT. Immunohistochemical analysis demonstrated marked immunoreactivity of 17beta-hydroxysteroid dehydrogenase (HSD17B5), an enzyme that can convert androstenedione to testosterone. Following surgical removal of the tumor, testosterone and free testosterone levels were markedly decreased (0.3 ng/ml and 0.4 pg/ml, respectively) and other symptoms abated. In conclusion, this is the first report of an ovarian MCT associated with clinical virilization caused by the ectopic production of testosterone possibly because of an overexpression of intratumoral HSD17B5.