Effects of chronic metabolic alkalosis on Ca2+, PTH, and 1,25(OH)2D3 in the rat

D. A. Bushinsky, M. K. Kittaka, J. R. Weisinger, C. B. Langman, M. J. Favus

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13 Scopus citations

Abstract

The effect of chronic metabolic alkalosis on arterial blood ionized calcium concentration ([Ca2+]) and the levels of serum parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] is difficult to predict. Although a fall in pH directly decreases [Ca2+], chronic alkalosis reduces uring calcium excretion, which could elevate [Ca2+]. [Ca2+] modulates the serum level of PTH and the level of 1,25(OH)2D3 directly and through PTH. To determine the effect of chronic metabolic alkalosis on [Ca2+], PTH, and 1,25(OH)2D3, rats were made alkalemic by feeding a chloride-deficient diet (LCl) or LCl with 75 mM NaHCO3 in the drinking water (LCl + HCO3-) and compared with controls fed a chloride-replete diet (NCl). Compared with NCl, after 8 days of LCl and LCl + HCO3- arterial pH and PTH rose and [Ca2+] fell. Serum 1,25(OH)2D3 tended to rise with LCl and rose with LCl + HCO3-. Serum 1,25(OH)2D3 was correlated inversely with [Ca2+] (r = -0.510, n = 54, P < 0.001) and with pH (r = -0.291, n = 57, P < 0.03) but not with PTH or phosphorus. Stepwise regression analysis indicated that [Ca2+] accounted for the majority of the variance of serum 1,25(OH)2D3. Chronic metabolic alkalosis induced by a low-chloride diet and HCO3- appears to increase serum PTH and 1,25(OH)2D3 through a fall in [Ca2+].

Original languageEnglish (US)
Pages (from-to)20/4
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume257
Issue number4
StatePublished - 1989

ASJC Scopus subject areas

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

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