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Estrogen deficiency worsened Ca balance via downregulation of epithelial Ca transport proteins in aged female rats
Author(s) -
Wong Man Sau,
Dong Xiaoli,
Zhang Yan
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.1053.5
Subject(s) - endocrinology , medicine , estrogen , ovariectomized rat , downregulation and upregulation , chemistry , estrogen receptor , trpv6 , calbindin , kidney , vitamin d and neurology , vitamin d deficiency , calcium , calcium metabolism , biology , biochemistry , cancer , breast cancer , gene
Estrogen deficiency impairs intestinal and renal Ca (re)absorption in the aged female rats. However, it is unclear if estrogen and vitamin D endocrine system interact to alter Ca transport in aging animals. Eleven‐month‐old female sham or ovariectomized (OVX) rats were fed either a low‐Ca (LCD; 0.1% Ca, 0.65% P) diet or a high‐Ca (HCD; 1.2% Ca, 0.65% P) diet for 12 weeks. The interactive effects of estrogen deficiency and endogenous 1, 25(OH) 2 D 3 on Ca balance, and the mRNA expression of Ca transport proteins in intestine and kidney were studied. The results showed that OVX rats fed with LCD resulted in negative Ca net balance. LCD suppressed serum Ca in OVX rats, but not in sham rats, resulting in the induction of serum PTH and serum 1,25(OH) 2 D 3 levels. The surge in serum 1, 25(OH) 2 D 3 levels in LCD‐fed OVX rats resulted in an increase in mRNA expression of intestinal transient receptor potential cation channel (TRPV6) and calbindin D 9K as well as renal vitamin D receptor, but was unable to restore Ca balance in vivo . In contrast, the negative Ca balance was associated with the suppression of intestinal plasma membrane Ca pump (PMCA1b) and renal TRPV5, Calbindin D 28K and PMCA1b mRNA expression in aged OVX rats. In conclusion, estrogen‐dependent and vitamin D‐independent downregulation of epithelial Ca transport protein expression might account for the negative Ca balance in aged female OVX rats. Funding sources: Niche Area Research Scheme (1‐BB8N) and Research Studentship from The Hong Kong Polytechnic University.