Heuser, Alexander , Eisenhauer, Anton , Scholz-Ahrens, Katharina E. and Schrezenmeir, Jürgen (2016) Biological fractionation of stable Ca isotopes in Göttingen minipigs as a physiological model for Ca homeostasis in humanS. Isotopes in Environmental and Health Studies, 52 (6). pp. 633-648. DOI 10.1080/10256016.2016.1151017.

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Abstract

In order to investigate fractionation of calcium (Ca) isotopes in vertebrates as a diagnostic tool to detect Ca metabolism dysfunction we analyzed the Ca isotopic composition (δ44/40Ca = [(44Ca/40Ca)sample/(44Ca/40Ca)reference]−1) of diet, faeces, blood, bones and urine from Göttingen minipigs, an animal model for human physiology. Samples of three groups were investigated: 1. control group (Con), 2. group with glucocorticosteroid induced osteoporosis (GIO) and 3. group with Ca and vitamin D deficiency induced osteomalacia (−CaD). In contrast to Con and GIO whose average δ44/40Cafaeces values (0.39 ± 0.13‰ and 0.28 ± 0.08‰, respectively) tend to be lower than their diet (0.47 ± 0.02‰), δ44/40Cafaeces of −CaD (−0.27 ± 0.21‰) was significantly lower than their δ44/40Cadiet (0.37 ± 0.03‰), but also lower than δ44/40Cafaeces of Con and GIO. We suggest that the low δ44/40Cafaeces of −CaD might be due to the contribution of isotopically light Ca from gastrointestinal fluids during gut passage. Assuming that this endogenous Ca source is a common physiologic feature, a fractionation during Ca absorption is also required for explaining δ44/40Cafaeces of Con and GIO. The δ44/40Caurine of all groups are high (>2.0‰) reflecting preferential renal reabsorption of light Ca isotopes. In Göttingen minipigs we found a Ca isotope fractionation between blood and bones (Δ44/40Cablood-bone) of 0.68 ± 0.15‰.

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