title: Preclinical screening of the applicability of strontium as a marker for intestinal calcium absorption.
abstract: The applicability of stable strontium as a marker for measuring intestinal calcium absorption is mainly dependent on the validity of the assumption that calcium and strontium are absorbed with a constant ratio. Up to now, it is not clear whether this ratio is affected by intervention therapy. Therefore, preclinical screening of this ratio before and after treatment is indispensable for a clinical calcium absorption test based on the use of stable strontium as a marker. We studied the effects of 1,25-dihydroxyvitamin D3 [1,25(OH)2D(3)], a potent enhancer of active intestinal calcium absorption, on the pharmacokinetics of both calcium-45 and strontium in adult male rats, in a short-term dose-finding study [0-50 ng 1,25(OH)2D(3)/100 g body weight] and also in a placebo-controlled study in which 12.5 ng 1,25(OH)2D(3)/100 g body weight were applied to assess the long-term pharmacokinetics. The mean bioavailability (true absorption) was 33% for calcium and 19% for strontium (ratio 1.7:1), whereas, after 1,25(OH)2D(3) pretreatment, it was 73 and 43% (ratio 1.7:1), respectively. These findings demonstrate that intestinal strontium absorption has, like intestinal calcium absorption, an active component. Moreover, they underscore the applicability of stable strontium as a tool for investigating calcium absorption under various conditions.
authors.affiliation: Department of Endocrinology, University Hospital Vrije Universiteit, Amsterdam, The Netherlands.
authors.forename: A J
authors.initials: AJ
authors.lastname: Sips
authors.forename: R
authors.initials: R
authors.lastname: Barto
authors.forename: J C
authors.initials: JC
authors.lastname: Netelenbos
authors.forename: W J
authors.initials: WJ
authors.lastname: van der Vijgh
mesh_terms: D000818:Animals; D015415:Biomarkers; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism* / Q000493:pharmacokinetics; D007408:Intestinal Absorption / Q000187:drug effects*; D008297:Male; D010710:Phosphates / Q000097:blood; D051381:Rats; D017208:Rats, Wistar; D013324:Strontium / Q000493:pharmacokinetics
chemical_list: D015415:Biomarkers; D010710:Phosphates; D002117:Calcitriol; D002118:Calcium; D013324:Strontium