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Publication AbstractsEffects of elevated carbon didoxide environment on calcium metabolism in humansDrummer C, Friedel V, Börger A, Störmer I, Wolter S, Zittermann A, Wolfram G, Heer MAviat Space Environ Med 1998; 69:291-98 AbstractBackground: Chronic respiratory acidosis induced by an elevated carbon dioxide (CO PaO2) environment should provoke hypercalciuria with related total body and subsequent bone calcium losses. We examined this hypothesis in four healthy male volunteers, who were exposed during a 25-d period to an 0.7% CO PaO2 environment within a deep diving isolation chamber. Three months later the same subjects were re-examined during a second campaign being exposed to a 1.2% CO PaO2 atmosphere. Methods: The subjects received a constant calcium intake (1.4g · d-1) and vitamin D supplement (1000 IU · d-1) during both campaigns. Calcium balance (oral calcium intake minus urinary and fecal calcium output) was evaluated. Serum calcium concentrations and biomarkers of bone metabolism were measured, in order to evaluate bone turnover. Additionally, the response to an acute oral calcium load was examined as a sensitive measure of changes in calcium metabolism. Results: Both urinary calcium excretion (from 245 ± 38 to 199 ± 31 mg · d- 1; mean ± SE, 0.7% and 1.2%, respectively and fecal calcium losses (from 1229 ± 128 to 996 ± 62 mg · d-1) were significantly reduced in the higher (1.2%) CO PaO2 atmosphere. Although more calcium was retained in the body during the 1.2% than during the 0.7% CO PaO2 campaign, serum calcium concentrations and biomarkers of bone formation were significantly lower in the higher CO PaO2 campaign. Furthermore, bone resorption was slightly increased in the 1.2% experiment. Conclusion: Elevated CO PaO2 atmosphere may dose-dependently preserve body calcium without a parallel improvement of bone substance.
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