Ovariectomy worsens secondary hyperparathyroidism in mature rats during low-Ca diet

Yan Zhang, Wan Ping Lai, Chun Fu Wu, Murray J. Favus, Ping Chung Leung, Man Sau Wong

Research output: Journal article publicationJournal articleAcademic researchpeer-review

31 Citations (Scopus)

Abstract

Estrogen deficiency impairs intestinal Ca absorption and induces bone loss, but its effects on the vitamin D-endocrine system are unclear. In the present study, calciotropic hormones levels, renal vitamin D metabolism, 1,25-dihydroxyvitamin D3[1,25(OH)2D3]- dependent intestinal calcium absorption, and bone properties in 3-mo-old sham-operated (sham) or ovariectomized (OVX) rats fed either a normal-Ca (NCD; 0.6% Ca, 0.65% P) or a low-Ca (LCD; 0.1% Ca, 0.65% P) diet for 2 wk were determined. LCD increased serum 1,25(OH)2D3levels in both sham and OVX rats. Serum parathyroid hormone [PTH(1-84)] levels were highest in OVX rats fed LCD. Renal 25-hydroxyvitamin D1α-hydroxylase (1-OHase) protein expression was induced in both sham and OVX rats during LCD, while renal 1-OHase mRNA expression was highest in OVX rats fed LCD. Renal vitamin D receptor (VDR) and mRNA expressions in rats were induced by ovariectomy in rats fed NCD but suppressed by ovariectomy in rats fed LCD. The induction of intestinal calcium transporter-1 and calbindin-D9k mRNA expressions by LCD were not altered by ovariectomy. As expected, bone Ca content, cancellous bone mineral density, and bone strength index in proximal metaphysis of rat tibia were reduced by both ovariectomy and LCD (P < 0.05) as analyzed by two-way ANOVA. Taken together, the data demonstrate that ovariectomy alters the responses of circulating PTH levels, renal 1-OHase mRNA expression, and renal VDR expression to LCD. These results suggest that estrogen is necessary for the full adaptive response to LCD mediated by both PTH and 1,25(OH)2D3.
Original languageEnglish
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume292
Issue number3
DOIs
Publication statusPublished - 1 Mar 2007

Keywords

  • Dietary Ca restriction
  • Parathyroid hormone
  • Renal 25-hydroxyvitamin D1α-hydroxylase
  • Renal vitamin D receptor

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)

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