Danisi G, Bonjour J P, Straub R W
Pflugers Arch. 1980 Dec;388(3):227-32. doi: 10.1007/BF00658486.
Animals teated with disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP), at doses which decrease the renal production and/or the plasma levels of 1,25-dihydroxycholecalciferol [1,25(OH)2D3], display a reduced net absorption of phosphate. In this study we investigated whether EHDP-treatment and administration of 1,25(OH)2D3 to EHDP-treated animals affected the phosphate influx across the mucosal border of rabbit duodenum. The initial rate of phosphate influx into mucosal cells was measured in isolated intestine. In control, untreated rabbits, the phosphate influx shows a saturable, Na-dependent component and a diffusional, Na-independent uptake. In tissue from rabbits treated for 3 days with EHDP, the phosphate influx was found to be strongly reduced. EHDP-treatment decreased the Na-dependent, carrier mediated phosphate influx in duodenum. Administration of 1,25(OH)2D3 to EHDP-treated animals reversed the reduced phosphate influx. These effects were mainly apparent through changes in the J(mc)(max) of the phosphate influx, which was decreased from 211 +/- 38.7 nmol/cm2h in controls to 42.1 +/- 18.1 nmole/cm2 h in the EHDP-treated group and increased to 413 +/- 43.6 nmole/cm2 h by 1,25(OH)2D3. The treatment did not appear to affect the diffusional, Na-independent phosphate influx. EHDP-treatment did not affect the influx of alanine in this segment suggesting that EHDP-treatment affects only 1,25(OH)2D3-dependent transport mechanisms. The results suggest that 1,25(OH)2D3 modulates the number of carrier sites available at the mucosal membrane for Na-dependent phosphate entry.
用乙烷-1-羟基-1,1-二膦酸二钠（EHDP）治疗的动物，其剂量能降低肾脏产生和/或血浆中1,25-二羟基胆钙化醇[1,25(OH)₂D₃]的水平，表现出磷酸盐净吸收减少。在本研究中，我们调查了EHDP治疗以及给用EHDP治疗的动物施用1,25(OH)₂D₃是否会影响兔十二指肠黏膜边界的磷酸盐流入。在分离的肠段中测量磷酸盐流入黏膜细胞的初始速率。在对照的未治疗兔中，磷酸盐流入显示出一个可饱和的、依赖钠的成分以及一个扩散性的、不依赖钠的摄取。在用EHDP治疗3天的兔组织中，发现磷酸盐流入大幅减少。EHDP治疗降低了十二指肠中依赖钠的、载体介导的磷酸盐流入。给用EHDP治疗的动物施用1,25(OH)₂D₃可逆转减少的磷酸盐流入。这些效应主要通过磷酸盐流入的J(mc)(max)变化而显现，其从对照组的211±38.7 nmol/cm²h降至EHDP治疗组的42.1±18.1 nmole/cm²h，并通过1,25(OH)₂D₃增加至413±43.6 nmole/cm²h。该治疗似乎未影响扩散性的、不依赖钠的磷酸盐流入。EHDP治疗未影响该段中丙氨酸的流入，表明EHDP治疗仅影响依赖1,25(OH)₂D₃的转运机制。结果表明，1,25(OH)₂D₃调节黏膜膜上可用于依赖钠的磷酸盐进入的载体位点数量。
