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Magnesium stimulates renal phosphate reabsorption


Thumfart, J; Jung, S; Amasheh, S; Kraemer, S; Peters, H; Sommer, K; Biber, J; Murer, H; Meij, I; Querfeld, U; Wagner, C A; Muller, D N (2008). Magnesium stimulates renal phosphate reabsorption. American Journal of Physiology. Renal Physiology, 295:F1126-F1133.

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.

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.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Center for Integrative Human Physiology
04 Faculty of Medicine > Institute of Physiology
07 Faculty of Science > Institute of Physiology
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:August 2008
Deposited On:19 Sep 2008 13:13
Last Modified:05 Apr 2016 12:28
Publisher:American Physiological Society
ISSN:0363-6127
Publisher DOI:10.1152/ajprenal.00353.2007
PubMed ID:18701629
Permanent URL: http://doi.org/10.5167/uzh-3758

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