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Parmita Kar and Ravinder Goswami

( Goswami et al. 2012 ). The interactive effect of high phosphate and low calcitriol on BGC in ‘drug-naïve’ state and any subsequent change following conventional therapy is difficult to evaluate in hypoparathyroid patients for ethical aspects

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Kumi Futawaka, Tetsuya Tagami, Yuki Fukuda, Rie Koyama, Ayaka Nushida, Shoko Nezu, Hironori Yamamoto, Miyuki Imamoto, Masato Kasahara, and Kenji Moriyama

diseases ( Matsumoto et al. 1990 , Brown & Coyne 2002 , Morii et al. 2004 , Tsukamoto 2004 , O’Neill & Feldman 2010 ). Among the VD 3 analogs, calcitriol is the physiologically active form of VD 3 , and alfacalcidol is a prodrug that requires

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Raphaela Rid, Martin Wagner, Christina J Maier, Harald Hundsberger, Helmut Hintner, Johann W Bauer, and Kamil Önder

, enucleated stratum corneum skin surface ( Lu et al . 2005 , Carlberg & Seuter 2007 , Bikle 2010 ). A central regulator of keratinocyte (and also of other normal vs malignant cell types) growth and differentiation is hereby calcitriol (1α,25

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C Demers, J Lemay, G N Hendy, and M Gascon-Barré


Although the kidney and intestine are among the major organs involved in both the biotransformation and action of vitamin D3, they exhibit very distinct roles in calcium and D3 homeostasis. The aim of the present studies was to investigate the relative in vivo responsiveness of renal and intestinal 1,25(OH)2D3-24-hydroxylase (24-hydroxylase) mRNA levels to calcitriol (1,25(OH)2D3) following acute or chronic 1,25(OH)2D3 exposure using hypocalcemic vitamin D-depleted rats as an experimental model. Intestinal 24-hydroxylase mRNA levels were very responsive to a single i.v. injection of 2·4, 12 or 120nmol 1,25(OH)2D3/kg but in kidney the mRNA levels only increased following exposure to the highest 1,25(OH)2D3 concentration, and exhibited a maximum response only 30% of that in the intestine despite similar tissue uptake of the hormone. To evaluate whether the kidney might preferentially respond to endogenously produced 1,25(OH)2D3, animals received increasing doses of 25(OH)D3. Although the intestinal 24-hydroxylase transcript was highly induced, the renal transcript was unresponsive to 25(OH)D3 treatment despite circulating 1,25(OH)2D3 concentrations of 24 nmol/l. By contrast, intestinal 24-hydroxylase mRNA levels were largely unresponsive to long-term calcitriol administration while the renal transcript, although insensitive to a physiological dose, responded to pharmacological 1,25(OH)2D3 doses. However, when challenged acutely with 1,25(OH)2D3 following chronic exposure, the kidney 24-hydroxylase mRNA levels remained largely unresponsive in contrast to the intestinal transcript which was markedly induced. These data indicate that significant differences exist in the in vivo tissue responsiveness of the 24-hydroxylase mRNA. Indeed, the gene exhibited high intestinal responsiveness to acutely, but not chronically, administered 1,25(OH)2D3, while in the kidney it only responded to high exogenous 1,25(OH)2D3 delivered either acutely or chronically. In addition, these site-specific regulatory mechanisms governing the expression of the 24-hydroxylase gene are independent of the endocrine calcium status and render the kidney relatively resistant to endogenously produced 1,25(OH)2D3.

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Sang R Lee, Mi-Young Park, Hyun Yang, Geun-Shik Lee, Beum-Soo An, Bae-kuen Park, Eui-Bae Jeung, and Eui-Ju Hong

) expression correlates inversely with serum sex steroid levels ( Iida et al . 1995 ), while estrogen influences the expression of enzymes involved in 1α,25-dihydroxyvitamin D 3 (calcitriol) production and metabolism ( Lechner et al . 2006 ). As the major

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René Lafont, Maria Serova, Blaise Didry-Barca, Sophie Raynal, Louis Guibout, Laurence Dinan, Stanislas Veillet, Mathilde Latil, Waly Dioh, and Pierre J Dilda

et al. 2009 )), MARRS (a calcitriol receptor ( Khanal & Nemere 2007 )) or drosophila DopEcR (a dopamine and ecdysteroid membrane receptor ( Evans et al. 2014 )). All these receptors belong to the family of GPCR/7TD receptors. Moreover, intact or

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Yuichiro Takei, Hironori Yamamoto, Masashi Masuda, Tadatoshi Sato, Yutaka Taketani, and Eiji Takeda

, hypercalcemia, and hyperphosphatemia ( Kuro-o et al . 1997 , Yoshida et al . 2002 ). However, Honda et al . (1999) have documented that renal Stc2 mRNA expression is reduced by calcitriol, the active form of vitamin D 3 , in rats. Thus, the regulatory

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Bryan B Ho and Clemens Bergwitz

(PTH), regulates phosphate recycling and synthesis of calcitriol (1,25-Dihydroxyvitamin D or 1,25(OH) 2 D) in the kidneys ( Shimada et al. 2004 ). Canonical FGF23 signalling requires the obligatory co-receptor alpha KLOTHO (KL), a transmembrane

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Xiang Zhang and Shuk-Mei Ho

of endocrine disorders. Epigenetic regulation of the action of steroid hormones, thyroid hormones, retinoic acid, and calcitriol A recent review has discussed certain aspects of epigenetic regulation of the expression of genes involved in steroid

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I Hendrix, P H Anderson, J L Omdahl, B K May, and H A Morris

alpha-hydroxylase (CYP27B1). Bone 32 332 –340. Dusso A , Brown A & Slatopolsky E 1994 Extrarenal production of calcitriol. Seminars in Nephrology 14 144 –155. Favus MJ & Langman CB