Sips A J, Barto R, Netelenbos J C, van der Vijgh W J
Department of Endocrinology, University Hospital Vrije Universiteit, Amsterdam, The Netherlands.
Am J Physiol. 1997 Mar;272(3 Pt 1):E422-8. doi: 10.1152/ajpendo.1997.272.3.E422.
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.
稳定锶作为测量肠道钙吸收标志物的适用性主要取决于钙和锶以恒定比例吸收这一假设的有效性。到目前为止，尚不清楚该比例是否受干预治疗的影响。因此，对于基于使用稳定锶作为标志物的临床钙吸收试验而言，治疗前后对该比例进行临床前筛查是必不可少的。在一项短期剂量探索研究[0 - 50 ng 1,25(OH)₂D₃/100 g体重]以及一项安慰剂对照研究（应用12.5 ng 1,25(OH)₂D₃/100 g体重以评估长期药代动力学）中，我们研究了活性肠道钙吸收的强效增强剂1,25 - 二羟基维生素D₃[1,25(OH)₂D₃]对成年雄性大鼠体内钙 - 45和锶药代动力学的影响。钙的平均生物利用度（实际吸收）为33%，锶为19%（比例为1.7:1），而在1,25(OH)₂D₃预处理后，分别为73%和43%（比例为1.7:1）。这些发现表明，肠道锶吸收与肠道钙吸收一样，具有一个活性成分。此外，它们强调了稳定锶作为在各种条件下研究钙吸收工具的适用性。
