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K. Ohta, Y. Hirata, T. Imai, and F. Marumo


To elucidate whether anterior pituitary cells express the nitric oxide (NO) synthase gene, we studied the synthesis of NO and the expression of NO synthase (NOS) mRNA by a mouse pituitary tumour cell line (AtT20/D16). Interleukin-1β (IL-1β) stimulated production of NO2 /NO3 (NOx) in a time-dependent manner and both NOx and cyclic GMP formation were stimulated in a dose-dependent manner by IL-1β. IL-1β-induced NOx production and intracellular cyclic GMP formation were similarly blocked by an NO synthase inhibitor, NG-monomethyl-l-arginine (LNMMA), whose effect was reversed by l-arginine, but not by d-arginine. Dexamethasone inhibited IL-1β-induced NOx production in a dose-dependent manner. A calmodulin inhibitor (W-7) showed no effect on IL-1β-induced NOx production, whereas cycloheximide and the actinomycin D completely inhibited NOx production. Northern blot analysis using cDNA for mouse macrophage-inducible NOS as a probe revealed the expression of inducible NOS mRNA in the cells only after exposure to IL-1β. Although IL-1β stimulated ACTH release from tumour cells, LNMMA failed to affect ACTH release stimulated by IL-1β. These results demonstrate for the first time that a pituitary tumour cell line (AtT20/D16) possesses cytokine-inducible and Ca2+/calmodulin-independent NOS, although NO may not be involved in ACTH release.

Journal of Endocrinology (1993) 138, 429–435

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A Okada, Y Ohta, SL Brody, and T Iguchi

Expression of transcription factors binding to the activating protein-1 (AP-1) site is induced by estrogens in association with epithelial proliferation in the uterus, but, in the oviduct, the relationship between cell proliferation and differentiation and AP-1 transcription factors is not well understood. In the developing rat oviduct, we found that proliferation and differentiation of epithelial cells were region-dependently regulated by 17beta-estradiol (E2). To determine the role of AP-1 transcription factors in the development of rat oviduct, we performed immunohistochemistry for epithelial c-jun and c-fos proteins in E2-untreated and -treated newborn rats. E2 increased the expression of c-jun and c-fos during proliferation of undifferentiated epithelial cells, but diminished both proteins during accelerated differentiation of ciliated epithelial cells. A pure estrogen receptor (ER) antagonist, ICI 182,780, inhibited changes in their expression during both cell proliferation and differentiation. Importantly, no reduction of c-jun was noted in the epithelial cells of the foxj1-deficient oviduct, which lacks cilia development. This study shows that c-jun and c-fos are regulated during epithelial cell proliferation and differentiation in a region-specific manner. This provides critical information for understanding the molecular and cellular mechanisms of the development of the neonatal oviduct.

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J Doi, H Takemori, M Ohta, Y Nonaka, and M Okamoto

Epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) are pluripotent growth factors that stimulate both the proliferation and steroidogenesis of adrenocortical cells. Here we demonstrate that EGF and bFGF specifically induce mRNA of 3beta-hydroxysteroid dehydrogenase type II (3betaHSD II) and suppress that of 17alpha-hydroxylase/lyase P450 (CYP17) in human adrenocortical H295R cells. The induction of 3betaHSD II mRNA did not occur until 6 h after the growth factor treatment and was completely abolished in the presence of a protein synthesis inhibitor, cycloheximide (CHX), suggesting that the induction required de novo protein synthesis. The CYP17 mRNA suppression began at almost the same time as the induction of the 3betaHSD II mRNA. Interestingly, the CYP17 mRNA level was increased by the CHX treatment. Both the 3betaHSD II and CYP17 mRNAs were repressed by treatment with a calmodulin kinase II (CaMK II) inhibitor, KN-93, and were enhanced by a mitogen-activated protein kinase (MAPK) inhibitor, PD98059. The PD98059-mediated induction of the 3betaHSD II mRNA was completely blocked by the CHX treatment. Interestingly, treatment with EGF in the presence of both PD98059 and CHX produced a greater increase in the CYP17 mRNA than did treatment in the presence of PD98059 alone. These results suggest that CHX-sensitive factor(s) and CaMK II- and MAPK-signaling pathways may have important roles in both induction of 3betaHSD II and suppression of CYP17 by EGF or bFGF in H295R cells.

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A Okada, T Sato, Y Ohta, DL Buchanan, and T Iguchi

To evaluate mechanisms of cell proliferation in the fetal female rat reproductive tract, diethylstilbestrol (DES) effects on cell division and estrogen receptor (ER), epidermal growth factor (EGF) and EGF receptor (EGF-R) expressions were determined from gestational day (GD) 15.5 to 21.5. Reproductive tracts were evaluated within three regions along the Mullerian duct axis; these were proximal, middle and caudal, which differentiate into oviduct, uterus and upper vagina respectively. In fetuses from non-treated dams, epithelial and mesenchymal proliferation, as evaluated by 5-bromo-2'-deoxyuridine incorporation, was decreased with development in all regions of the Mullerian duct. EGF levels were determined by immunohistochemistry. Mullerian epithelial EGF immunoreactivity was intense in the proximal and middle regions on GDs 15.5 and 17.5. EGF staining remained intense only in the proximal epithelia by GD 19.5 and was weak in the caudal epithelium, but substantially reduced throughout epithelia in all regions by GD 21.5. Thus, decreased cell proliferation correlated with decreased EGF expression in the developing Mullerian duct. DES (100 microg/kg body weight) was injected from GD 15 to 19 and female fetuses were collected on GD 19.5. DES increased Mullerian duct cell proliferation in the proximal epithelium and mesenchyme but decreased it in the caudal epithelium compared with oil-treated controls. No proliferative DES effect was observed in any cell type in the middle region. Mullerian duct EGF immunoreactivity was suppressed by DES compared with oil. Competitive RT-PCR indicated DES also decreased mRNAs for EGF, ERbeta1 and ERbeta2, but not ERalpha and EGF-R. These results indicate EGF may be an important regulatory factor of Mullerian duct cell proliferation, and that DES may alter cell proliferation by disrupting normal EGF, ERbeta1 and ERbeta2 expression in the developing female rat reproductive tract.