Benech H, Grognet J M
Commissariat a l'Energie Atomique (CEA), Service de Pharmacologie et d'Immunologie, Gif sur Yvette, France.
Magnes Res. 1995 Sep;8(3):277-84.
Assessment of the bioavailability of exogenous ions present in a large amounts in the body, such as magnesium, cannot be performed by the conventional measurement of plasma levels after intravenous and/or oral administration. In the case of magnesium, this is emphasized by the fact that plasma levels are quickly regulated, mainly by the kidney and in storage compartments such as bone, after exogenous administration. Magnesium bioavailability and absorption are studied by indirect methods or by using radioactive or stable isotopes as tracers. Indirect methods are the metabolic balance method and comparison of urinary excretion between a treatment and a placebo period, often after magnesium load. However, the former only measures magnesium absorption and the latter is subject to the fragile balance of magnesium urinary excretion. Isotope studies, in particular with stable isotope probes, have benefited from the developments in mass spectrometry, such as inductively coupled plasma mass spectrometry (ICP-MS). It is possible to follow exogenous magnesium in plasma after oral and intravenous administrations using 25Mg and 26Mg as tracers, and to calculate the absolute bioavailability of magnesium.
对于体内大量存在的外源离子（如镁），不能通过静脉内和/或口服给药后常规测量血浆水平来评估其生物利用度。就镁而言，外源给药后血浆水平会迅速调节，主要通过肾脏以及骨骼等储存部位进行调节，这一事实突出了这一点。镁的生物利用度和吸收通过间接方法或使用放射性或稳定同位素作为示踪剂来研究。间接方法包括代谢平衡法以及在镁负荷后，比较治疗期和安慰剂期的尿排泄情况。然而，前者仅测量镁的吸收，而后者受镁尿排泄脆弱平衡的影响。同位素研究，特别是使用稳定同位素探针的研究，受益于质谱技术的发展，如电感耦合等离子体质谱（ICP-MS）。使用²⁵Mg和²⁶Mg作为示踪剂，可以在口服和静脉给药后追踪血浆中的外源镁，并计算镁的绝对生物利用度。
