Dai L J, Bapty B, Ritchie G, Quamme G A
Department of Medicine, University of British Columbia, Vancouver Hospital and Health Sciences Centre, Koerner Pavilion, Vancouver, British Columbia, Canada V6T 1Z3.
Am J Physiol. 1998 Nov;275(5):F833-9. doi: 10.1152/ajprenal.1998.275.5.F833.
Prostaglandins have diverse effects on renal electrolyte reabsorption, inhibiting NaCl absorption in the thick ascending limb and modulating sodium and calcium transport in cortical collecting cells. It is unclear what effect, if any, prostaglandins have on tubular magnesium handling. The effects of prostaglandin E2 (PGE2) were studied on immortalized mouse distal convoluted tubule (MDCT) cells by measuring cellular cAMP formation with radioimmunoassays and Mg2+ uptake with fluorescence techniques. Intracellular free Mg2+ concentration ([Mg2+]i) was measured on single MDCT cells using microfluorescence with mag-fura 2. To assess Mg2+ uptake, MDCT cells were first Mg2+ depleted to 0.22 +/- 0.01 mM by culturing in Mg2+-free media for 16 h and then placed in 1.5 mM MgCl2, and the changes in [Mg2+]i were determined. [Mg2+]i returned to basal levels, 0.53 +/- 0.02 mM, with a mean refill rate, d([Mg2+]i)/dt, of 173 +/- 8 nM/s. Indomethacin, 5 microM, diminished basal Mg2+ uptake, suggesting that endogenous prostaglandins may stimulate Mg2+ entry in control cells. PGE2 stimulated Mg2+ entry in a concentration-dependent manner with maximal response of 311 +/- 12 nM/s, at a concentration of 10(-7) M, which represented an 80 +/- 3% increase in uptake rate above control values. This was associated with a sixfold increase in intracellular cAMP generation. PGE2-stimulated Mg2+ uptake was completely inhibited with the Rp diastereoisomer of adenosine 3',5'-cyclic monophosphothionate (Rp-cAMPS), a protein kinase A inhibitor, and U-73122, a phospholipase C inhibitor, and partially by chelerythrine, a protein kinase C inhibitor. Accordingly, PGE2-mediated Mg2+ entry rates involve multiple intracellular signaling pathways. These studies demonstrate that PGE2 stimulates Mg2+ uptake in a cell line of MDCT.
前列腺素对肾脏电解质重吸收具有多种作用，可抑制髓袢升支粗段对氯化钠的重吸收，并调节皮质集合管中钠和钙的转运。目前尚不清楚前列腺素对肾小管镁处理有何种影响（如果有影响的话）。通过放射免疫测定法测量细胞内环磷酸腺苷（cAMP）的形成，并使用荧光技术测量镁离子（Mg2+）摄取，研究了前列腺素E2（PGE2）对永生化小鼠远曲小管（MDCT）细胞的影响。使用mag-fura 2通过显微荧光法测量单个MDCT细胞内的游离镁离子浓度（[Mg2+]i）。为了评估镁离子摄取，首先将MDCT细胞在无镁培养基中培养16小时，使其镁离子浓度降至0.22±0.01 mM，然后置于1.5 mM氯化镁中，测定[Mg2+]i的变化。[Mg2+]i恢复到基础水平，即0.53±0.02 mM，平均再填充速率d([Mg2+]i)/dt为173±8 nM/s。5 microM的吲哚美辛降低了基础镁离子摄取，这表明内源性前列腺素可能刺激对照细胞中的镁离子进入。PGE2以浓度依赖性方式刺激镁离子进入，在浓度为10(-7) M时最大反应为311±12 nM/s，这表示摄取速率比对照值增加了80±3%。这与细胞内cAMP生成增加六倍有关。PGE2刺激的镁离子摄取被蛋白激酶A抑制剂3',5'-环磷酸腺苷硫代磷酸酯的Rp非对映异构体（Rp-cAMPS）和磷脂酶C抑制剂U-73122完全抑制，并被蛋白激酶C抑制剂白屈菜红碱部分抑制。因此，PGE2介导的镁离子进入速率涉及多种细胞内信号通路。这些研究表明，PGE2刺激MDCT细胞系中的镁离子摄取。
