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Magnesium stimulates renal phosphate reabsorption

Item Type:Article
Title:Magnesium stimulates renal phosphate reabsorption
Creators Name:Thumfart, J. and Jung, S. and Amasheh, S. and Kraemer, S. and Peters, H. and Sommer, K. and Biber, J. and Murer, H. and Meij, I.C. and Querfeld, U. and Wagner, C.A. and Mueller, D.
Abstract:In the kidney, about 80% of the filtered phosphate (Pi) is reabsorbed along the proximal tubule. Changes in renal Pi reabsorption are associated with modulation of the sodium dependent Pi cotransporter NaPi Type IIa (NaPi-IIa) and Type IIc (NaPi-IIc) protein abundance in the brush border membrane (BBM) of proximal tubule cells. NaPi-IIa is mainly regulated by dietary Pi intake and parathyroid hormone (PTH). The purpose of the present study was to elucidate the effect of alteration in dietary magnesium (Mg(2+)) intake on renal Pi handling. Urinary Pi excretion and renal expression of NaPi-IIa and NaPi-IIc were analyzed in rats fed with normal (0.2%) or high Mg(2+) (2.5%) diet. High Mg(2+) diet resulted in decreased renal Pi excretion and increased protein expression of NaPi-IIa and NaPi-IIc. Serum FGF-23 (fibroblast growth factor 23) levels were unchanged under high Mg(2+) diet. Serum PTH levels were slightly decreased under high Mg(2+) diet. To examine whether the observed changes in renal Pi reabsorption are PTH dependent, NaPi-IIa and NaPi-IIc expression were also analyzed in parathyroidectomized (PTX) rats fed with normal or high Mg(2+) diet. In PTX rats Mg(2+) had no significant effect on renal Pi excretion or NaPi-IIa protein expression. Mg(2+) increased NaPi-IIc protein expression in PTX rats. This experiment shows for the first time on the molecular level how Mg(2+) stimulates renal Pi reabsorption. Under high Mg(2+) diet NaPi-IIa expression is dependent on PTH levels, whereas NaPi-IIc expression seems to be independent from PTH levels. Key words: magnesium, NaPi-IIa, posphate reabsorption, NaPi-IIc.
Keywords:Parathyroid Hormone, Animal Feed, Fibroblast Growth Factors, Immunohistochemistry, Kidney, Linoleic Acids, Magnesium, Parathyroid Hormone, Parathyroidectomy, Phosphates, Messenger RNA, Type IIa Sodium-Phosphate Cotransporter Proteins, Type IIc Sodium-Phosphate Cotransporter Proteins, gamma-Linolenic Acid, Animals, Rats
Source:American Journal of Physiology Renal Physiology
Publisher:American Physiological Society (U.S.A.)
Page Range:F1126-1133
Date:9 October 2008
Official Publication:https://doi.org/10.1152/ajprenal.00353.2007
PubMed:View item in PubMed

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