Williams Katie Beth, DeLuca Hector F
Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Drive, Madison, WI 53706-1544, USA.
Am J Physiol Endocrinol Metab. 2007 Jun;292(6):E1917-21. doi: 10.1152/ajpendo.00654.2006. Epub 2007 Feb 13.
A new, completely in vivo method of measuring the rate of intestinal phosphate absorption has been developed. As expected from previous in vitro and ex vivo measurements, intestinal phosphate absorption is potently and rapidly stimulated by 1,25-dihydroxyvitamin D3. The response is saturated with as little as 11.3 ng of 1,25-dihydroxyvitamin D3 per day, consistent with a genomic mechanism. The effect of 1,25-dihydroxyvitamin D3 disappears when the dosing solution of phosphate is at 2 M, suggesting that 1,25-dihydroxyvitamin D3 stimulates active transport of phosphate but not diffusion of phosphate. Finally, unlike findings resulting from in vitro or ex vivo experiments, no evidence in vivo was obtained that phosphate absorption requires sodium or is inhibited by potassium.
一种全新的、完全在体内测量肠道磷酸盐吸收速率的方法已被开发出来。正如先前体外和离体测量所预期的那样，1,25 - 二羟基维生素D3能有效且迅速地刺激肠道磷酸盐吸收。每天仅需11.3纳克的1,25 - 二羟基维生素D3，反应就会饱和，这与基因组机制相符。当磷酸盐给药溶液浓度为2M时，1,25 - 二羟基维生素D3的作用消失，这表明1,25 - 二羟基维生素D3刺激的是磷酸盐的主动转运而非扩散。最后，与体外或离体实验的结果不同，在体内未获得磷酸盐吸收需要钠或受钾抑制的证据。
