Behar J
Am J Physiol. 1975 Dec;229(6):1590-5. doi: 10.1152/ajplegacy.1975.229.6.1590.
The effect of calcium on magnesium absorption was studied in the rat ileum in vivo. The increase in the luminal concentration of calcium led to a progressive decrease in magnesium absorption, which was accompanied by a parallel decrease in net sodium absorption. This calcium effect was also observed when sodium chloride was replaced by urea. However, a consistent correlation was observed between the magnitude of net magnesium absorption and the rates of net water absorption of all calcium concentrations. These findings suggest that calcium decreases magnesium absorption by a nonspecific reduction in membrane permeability to solutes that induce net water flow and are consistent with the concept that magnesium is transported by solvent "drag". The increase in the luminal concentration of calcium resulted in an increase in tissue accumulation of magnesium. This increase in tissue accumulation of magnesium was associated with a decrease in net sodium absorption and in the negativity of the transmural PD. These findings suggest an additional mechanism of magnesium transport operating independently of net water flow.
在大鼠回肠体内研究了钙对镁吸收的影响。肠腔内钙浓度的增加导致镁吸收逐渐减少，同时净钠吸收也平行下降。当用尿素替代氯化钠时，也观察到了这种钙效应。然而，在所有钙浓度下，净镁吸收量与净吸水量之间始终存在相关性。这些发现表明，钙通过非特异性降低对诱导净水流的溶质的膜通透性来减少镁吸收，这与镁通过溶剂“拖曳”运输的概念一致。肠腔内钙浓度的增加导致组织中镁的积累增加。组织中镁积累的增加与净钠吸收的减少和跨壁电位差的负值减小有关。这些发现提示了一种独立于净水流的镁运输的额外机制。
