Regulation by extracellular Na+ of cytosolic Mg2+ concentration in Mg2+‐loaded rat sublingual acini

FEBS Letters

Zhang, Guo H.¹  Melvin, James E.¹ 

[1] Department of Dental Research, University of Rochester, Rochester, NY 14642, USA

关键词: Salivary acini;    Mg2+ loading;    [Mg2+]i decrease;    Na+/Mg2+ antiport;    BAPTA;    bis(O-aminophenoxy)ethane-N;    N;    N′;    N′-tetraacetic acid;    BSA;    bovine serum albumin;    [Ca2+]i;    cytosolic free Ca2+ concentration;    db-cAMP;    6;    2′-O-dibutyladenosine 3′;    5′-cyclic monophosphate;    Hepes;    4-(2-hydroxyethyl)-1-piperazine ethanesulphonic acid;    [Mg2+]i;    cytosolic free Mg2+ concentration;    NMDG;    N-methyl-d-glucamine;    PSS;    physiological salt solution;   

DOI  :  10.1016/0014-5793(95)00869-B

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The regulation of cytosolic free Mg²⁺ concentration ([Mg²⁺]_i) in Mg²⁺-loaded rat sublingual mucous acini was examined using the Mg²⁺-sensitive fluorescent indicator mag-fura-2. Loading sublingual acini with 5 mM Mg²⁺ elevated the [Mg²⁺]_i from 0.35 ± 0.01 mM to 0.66 ± 0.01 mM. Removal of extracellular Mg²⁺ resulted in a significantly faster [Mg²⁺]_i decrease in Mg²⁺-loaded rcini than in unloaded acini. Membrane depolarization with high extracellular [K⁺] and inhibition of P-type ATPases by vanadate did not alter the [Mg²⁺]_i decrease, indicating that the Mg²⁺ efflux mechanism is not electrogenic. Na⁺-free medium inhibited 80% of the [Mg²⁺]_i decrease suggesting that a Na⁺-dependent Mg²⁺ efflux pathway mediates the [Mg²⁺]_i decrease. Accordingly, the Na⁺-dependent antiport inhibitor quinidine reduced > 80% of the [Mg²⁺]_i decrease, suggesting that the Na⁺-dependent Mg⁺ efflux was also partly driven by K⁺. The [Mg⁺]_i system. Mg²⁺ efflux was also partly driven by K⁺. The [Mg²⁺]_i decrease was significantly inhibited by carbachol, a muscarinic agonist, but not by cAMP. These results indicate that in sublingual acinar cells a Na⁺-dependent pathway mediates Mg²⁺ efflux and that muscarinic stimulation may regulate Mg²⁺ extrusion.

【 授权许可】

Unknown