title: Magnesium homeostasis in cardiac myocytes of Mg-deficient rats.
abstract: To study possible modulation of Mg(2+) transport in low Mg(2+) conditions, we fed either a Mg-deficient diet or a Mg-containing diet (control) to Wistar rats for 1-6 weeks. Total Mg concentrations in serum and cardiac ventricular tissues were measured by atomic absorption spectroscopy. Intracellular free Mg(2+) concentration ([Mg(2+)]i) of ventricular myocytes was measured with the fluorescent indicator furaptra. Mg(2+) transport rates, rates of Mg(2+) influx and Mg(2+) efflux, were estimated from the rates of change in [Mg(2+)]i during Mg loading/depletion and recovery procedures. In Mg-deficient rats, the serum total Mg concentration (0.29±0.026 mM) was significantly lower than in control rats (0.86±0.072 mM) after 4-6 weeks of Mg deficiency. However, neither total Mg concentration in ventricular tissues nor [Mg(2+)]i of ventricular myocytes was significantly different between Mg-deficient rats and control rats. The rates of Mg(2+) influx and efflux were not significantly different in both groups. In addition, quantitative RT-PCR revealed that Mg deficiency did not substantially change mRNA expression levels of known Mg(2+) channels/transporters (TRPM6, TRPM7, MagT1, SLC41A1 and ACDP2) in heart and kidney tissues. These results suggest that [Mg(2+)]i as well as the total Mg content of cardiac myocytes, was well maintained even under chronic hypomagnesemia without persistent modulation in function and expression of major Mg(2+) channels/transporters in the heart.
authors.affiliation: Department of Physiology, Tokyo Medical University, Tokyo, Japan.
authors.forename: Michiko
authors.initials: M
authors.lastname: Tashiro
authors.forename: Hana
authors.initials: H
authors.lastname: Inoue
authors.forename: Masato
authors.initials: M
authors.lastname: Konishi
mesh_terms: D000818:Animals; D001692:Biological Transport; D001835:Body Weight; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism; D015870:Gene Expression; D006352:Heart Ventricles / Q000378:metabolism; D006706:Homeostasis; D008274:Magnesium / Q000097:blood / Q000378:metabolism*; D008275:Magnesium Deficiency / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008903:Minerals / Q000097:blood / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000378:metabolism*; D051381:Rats
chemical_list: D027682:Cation Transport Proteins; D008903:Minerals; D008274:Magnesium
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