Rubinger D, Krause I, Alkoby-Gibbs M, Popovtzer M M
Nephrology Service, Hadassah University Hospital, Jerusalem, Israel.
Bone Miner. 1991 Dec;15(3):219-26. doi: 10.1016/0169-6009(91)90127-l.
To better define the interaction between 1,25(OH)2D3 and 24,25(OH)2D3 in different states of renal function, the fractional absorption of Ca45 (FCa45) and plasma calcium (PCa) were determined in rats with intact kidneys and in rats with reduced renal mass after 5/6 nephrectomy. The two series of experiments were performed in control animals, and in rats treated with: 1) 1,25(OH)2D3, 54 ng/rat/day, 2) 24,25(OH)2D3 in the same dose, and 3) 1,25 and 24,25(OH)2D3 in the same (and equal) doses. In all animals 1,25(OH)2D3 administration was associated with a significant increase in PCa and in FCa45. In rats with normal renal function, however, 24,25(OH)2D3 enhanced and in rats with reduced renal mass it suppressed the hypercalcemic effect of 1,25(OH)2D3. These variations in PCa were not associated with further alteration in FCa45 which was similar after 1,25(OH)2D3 and after combined 1,25 and 24,25(OH)2D3 in normal rats and in rats with chronic renal failure. FCa45 was found to be of the same magnitude in rats with normal renal function and in rats with reduced renal mass. These results confirm previous findings of normal intestinal absorption of Ca in mild to moderate renal failure. The above data suggest that 24,25(OH)2D3 used in an equivalent dose does not influence the intestinal effects of 1,25(OH)2D3. Therefore, the interaction of 1,25 with 24,25(OH)2D3 in rats with intact kidneys or with reduced renal mass occurs at extra-intestinal sites.
为了更好地明确1,25(OH)₂D₃和24,25(OH)₂D₃在不同肾功能状态下的相互作用，对肾脏完整的大鼠以及5/6肾切除术后肾质量减少的大鼠测定了⁴⁵Ca的分数吸收(FCa₄₅)和血浆钙(PCa)。在对照动物以及接受以下处理的大鼠中进行了两组实验：1) 1,25(OH)₂D₃，54 ng/大鼠/天；2) 相同剂量的24,25(OH)₂D₃；3) 相同（且等量）剂量的1,25(OH)₂D₃和24,25(OH)₂D₃。在所有动物中，给予1,25(OH)₂D₃均与PCa和FCa₄₅的显著增加相关。然而，在肾功能正常的大鼠中，24,25(OH)₂D₃增强了1,25(OH)₂D₃的高钙血症作用，而在肾质量减少的大鼠中，它抑制了1,25(OH)₂D₃的高钙血症作用。PCa的这些变化与FCa₄₅的进一步改变无关，在正常大鼠和慢性肾衰竭大鼠中，1,25(OH)₂D₃给药后以及1,25(OH)₂D₃与24,25(OH)₂D₃联合给药后FCa₄₅相似。发现肾功能正常的大鼠和肾质量减少的大鼠的FCa₄₅大小相同。这些结果证实了先前关于轻度至中度肾衰竭时钙的肠道吸收正常的发现。上述数据表明，等量使用的24,25(OH)₂D₃不影响1,25(OH)₂D₃的肠道效应。因此，1,25(OH)₂D₃与24,25(OH)₂D₃在肾脏完整或肾质量减少的大鼠中的相互作用发生在肠道外部位。
