Duodenal villous hypertrophy and upregulation of claudin-15 protein expression in lactating rats
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ORIGINAL PAPER
Duodenal villous hypertrophy and upregulation of claudin-15 protein expression in lactating rats Kannikar Wongdee • Jarinthorn Teerapornpuntakit Chitchamai Siangpro • Sunitra Chaipai • Narattaphol Charoenphandhu
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Received: 8 August 2012 / Accepted: 14 September 2012 / Published online: 22 September 2012 Ó Springer Science+Business Media Dordrecht 2012
Abstract In lactation, the intestinal absorption of nutrients and minerals, especially calcium, is markedly enhanced to supply precursors for milk production. Little is known regarding the mechanism of this lactation-induced intestinal hyperabsorption. However, it has been postulated to result from villous hypertrophy with enlarged absorptive area and the upregulation of the cation-selective tight junction protein claudin-15, which could form calciumpermeable paracellular pores, thereby enhancing the paracellular calcium absorption. Here, we demonstrated in the duodenum of 21-day lactating rats that there were increases in the villous height, villous width and crypt depth, which together led to expansion of absorptive surface area. Quantitative real-time PCR further showed that the mRNA levels of claudin-10 and -15 were increased in the duodenal mucosal cells of lactating rats as compared to age-matched unmated control rats. However, immunohistochemical analysis revealed the lactation-induced upregulation of claudin-15, but not claudin-10 protein expression in the duodenal villous cells. The present results, therefore,
K. Wongdee J. Teerapornpuntakit N. Charoenphandhu Center of Calcium and Bone Research (COCAB), Faculty of Science, Mahidol University, Bangkok, Thailand K. Wongdee Office of Academic Management, Faculty of Allied Health Sciences, Burapha University, Chonburi, Thailand J. Teerapornpuntakit N. Charoenphandhu (&) Department of Physiology, Faculty of Science, Mahidol University, Rama VI Road, Bangkok 10400, Thailand e-mail: [email protected] C. Siangpro S. Chaipai Medical Science Program, Faculty of Allied Health Sciences, Burapha University, Chonburi, Thailand
corroborated the previous hypothesis that lactation induced intestinal absorption of calcium and perhaps other cation minerals, in part, by increasing villous absorptive area and claudin-15 protein expression. Keywords Claudin Duodenum Intestinal hypertrophy Lactation Tight junction
Introduction In lactating mammals, the enhanced intestinal absorption of nutrients and minerals, such as calcium, is crucial for milk production (Prentice 2000; Kovacs 2005; Charoenphandhu et al. 2010). Without adequate intestinal calcium supply, bone resorption is markedly enhanced to provide free-ionized calcium, thereby leading to osteoporosis and increased fracture risk (Prentice 2000; Kovacs 2005; Ofluoglu and Ofluoglu 2008). However, the mechanism of the lactation-induced intestinal nutrient and mineral absorption is not completely understood. One of the possible adaptive mechanisms includes hypertrophy and hyperplasia of the intestinal villi to increase the villous height, th
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