title: Immunosuppressants inhibit hormone-stimulated Mg2+ uptake in mouse distal convoluted tubule cells.
abstract: Immunosuppressants such as cyclosporinA and FK506 (tacrolimus) are widely prescribed to treat numerous disorders and to treat organ transplant recipients. However, cyclosporine A and FK506 are both known to produce hypomagnesaemia. The mechanism of this effect is still unclear. The present study determined the effects of immunosuppressant treatment on the parathyroid hormone (PTH) mediated Mg(2+) uptake and the mitogen-activated protein kinase (MAPK) activation in mouse distal convoluted tubule (MDCT) cells. The intracellular Ca(2+) and Mg(2+) concentrations in a single MDCT cell were measured by using the fluorescentdye Fura-2 AM and Mag-fura-2 AM, respectively. Cyclosporine A and FK506 illicited a transient increase of intracellular Ca(2+) from a basal level of 99 +/- 16 nM to 685 +/- 105 and 608 +/- 96 nM, respectively. In order to determine the Mg(2+) transport, the MDCT cells were Mg(2+)-depleted by culturing them in Mg(2+)-free media for 16 h, and the Mg(2+) uptake was measured by microfluorescence after placing the depleted cells in 1.5mM MgCl(2). The mean rate of Mg(2+) uptake, d([Mg(2+)](i))/dt, was 140 +/- 16 nM/s in the control MDCT cells. PTH increased the Mg(2+) uptake more than 2 times in this cell. Cyclosporine A (10 microM) and FK506 (0.1 microM) did not affect the basal Mg(2+)uptake (140 +/- 16 and 142 +/- 14 nM/s, respectively), but they inhibited the PTH-stimulated Mg(2+) entry, decreasing it from 248+/-12 to 147 +/- 7 and 148 +/- 14 nM/s, respectively. These effects were inhibited by L685818, which is a potent competitive antagonist of FK506. PTH stimulated the extracellular signal-regulated kinase1/2 (ERK1/2) protein synthesis. This PTH-stimulated ERK1/2 activation was inhibited by cyclosporine A and FK506. In the present study, the role of ERK1/2 activation on the PTH-dependent magnesium uptake was examined in MDCT cells, and we showed that immunosuppressants inhibit the hormone-stimulated Mg(2+) uptake into the MDCT cells by inhibiting the MAPK pathway.
authors.affiliation: College of Veterinary Medicine, Chonbuk National University, Jeonju 561-756, Republic of Korea.
authors.forename: Shang-Jin
authors.initials: SJ
authors.lastname: Kim
authors.forename: Hyung-Sub
authors.initials: HS
authors.lastname: Kang
authors.forename: Chang-Woo
authors.initials: CW
authors.lastname: Jeong
authors.forename: Sang-Yeol
authors.initials: SY
authors.lastname: Park
authors.forename: In-Shik
authors.initials: IS
authors.lastname: Kim
authors.forename: Nam-Soo
authors.initials: NS
authors.lastname: Kim
authors.forename: Sung-Zoo
authors.initials: SZ
authors.lastname: Kim
authors.forename: Yong-Geun
authors.initials: YG
authors.lastname: Kwak
authors.forename: Jin-Shang
authors.initials: JS
authors.lastname: Kim
authors.forename: Gary A
authors.initials: GA
authors.lastname: Quamme
mesh_terms: D000818:Animals; D002413:Cations, Divalent / Q000378:metabolism; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007686:Kidney Tubules, Distal / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010281:Parathyroid Hormone / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D016559:Tacrolimus / Q000494:pharmacology*
chemical_list: D002413:Cations, Divalent; D007166:Immunosuppressive Agents; D010281:Parathyroid Hormone; D016572:Cyclosporine; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D008274:Magnesium; D016559:Tacrolimus