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

Intracellular magnesium: transport and regulation in epithelial secretory cells

“…Further addition of Triton-X 100 (which permeabilizes the cytosolic organelles) produced small non-significant increases in [Mg 2+ ] o in both cases, indicating that the magnesium-loading procedure does not cause any significant redistribution of internal magnesium (45 Figure 1). This is in close agreement with the results obtained in a wide range of tissues: inhibition of Mg 2+ efflux by amiloride from preloaded cells has been shown in rat, pig and cow RBC (113), chicken RBC (114), rat thymocytes (115) and rat sublingual acini (39). In addition, in ferret RBC, which do not need a loading procedure for Mg 2+ efflux to be detected, significant inhibition of Mg 2+ efflux by amiloride, quinidine and imipramine has been reported (116).…”

“…Accordingly, using this approach, [Mg 2+ ] i between 0.9 and 1 mM have been reported in heart tissue as measured with Mg 2+ -selective microelectrodes (47)(48)(49) as well as in skeletal muscle as determined by 31 P NMRs (50). We observed a lower [Mg 2+ ] i (around 0.5 mM) in Magfura-loaded rat parietal cells (51), and studies with this probe give basal [Mg 2+ ] i values of approximately 0.25 mM for human platelets (37), 0.30-0.35 mM for human lymphocytes (52) and sublingual acinar cells (38,39), and 0.5 mM for renal epithelial cells and isolated hepatocytes (29,53).…”

“…Although it has been widely employed in many different cell types such as pancreatic beta cells (35), heart cells (28,36), platelets (37), and sublingual acinar cells (38,39), no studies have included a protocol for pancreatic tissue. A suitable method for loading pancreatic acinar cells was developed in our laboratory.…”

Na+-dependent Release of Mg2+ from an Intracellular Pool in Rat Sublingual Mucous Acini

“…exchange mechanism may be involved. The Na ϩ /Mg 2ϩ exchangers in several cell types are sensitive to quinidine (5,6,21). Fig.…”

“…Acutely raising or lowering the external [Mg 2ϩ ] has little effect on the total magnesium content of most cells suggesting that the plasma membrane has a very low Mg 2ϩ permeability (3,4). In cells artificially loaded with an elevated [Mg 2ϩ ] i , a plasma membrane Na ϩ /Mg 2ϩ exchanger is activated that shuts down when the [Mg 2ϩ ] i returns to resting levels (5,6). These results suggest that the primary function of Na ϩ /Mg 2ϩ exchange is to maintain the resting [Mg 2ϩ ] i .…”