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Gasser, S; Scherr, E; Gasser, R.
An ion-selective microelectrode study on the effect of acidification on free intracellular magnesium cardiac guinea pig papillary muscle
TRACE ELEM ELECTROLYTES. 2008; 25(1): 14-20. Doi: 10.5414/TEP25014
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Leading authors Med Uni Graz: Gasser Sandra Renate
Co-authors Med Uni Graz: Gasser Robert; Scherr Elisabeth
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Abstract:: It has been argued that a rise in free, unbound intracellular magnesium (Mg2+,) could be beneficial during myocardial ischemia, effecting the regulation of certain enzymes, the rectification of channels as well as intracellular Na+ and Ca2+. Mg2+ is a cofactor of the Na/K-ATPase, it competes with Ca2+ at the contractile apparatus etc. However, all of these properties are confined to the intracellular site. The present study investigates the effect of pH upon intracellular concentrations of Mg2+. Here we studied Mg-i(2+) with Mg2+-selective microelectrodes (ETH 7025) in isolated guinea pig papillary muscle. Free intracellular Mg-i(2+) in guinea pig papillary muscle was 0.73 +/- 0.08 (n = 7, +/- SEM) in the same type of tissue. These values are similar to those assessed earlier in sheep Purkinje fibre and ferret papillary muscle. In the present experiments we also changed extracellular pH from 7.4-6.4 and back to 7.4. In the same experiments, pH(i) has been measured using a pH-sensitive microelectrode in order to assess the change of pHi brought about by changing extracellular pH. This manoeuver led to a change of pHi from a resting level of 7.19 +/- 0.03 (n = 7, SEM) to 6.81 +/- 0.06 (n = 7, SEM). These changes of pH(i) led to a small but consistant rise of intracellular Mg2+. In 7 experiments Mg-i(2+) rose by 0.19 +/- 0.06 mM ( SEM) from an initial value of 0.73 +/- 0.21 mM. The small rise of Mg-i(2+) is likely to result from ionized Mg2+ being liberated from the Mg-ATP complex. Interestingly, despite pH had remained low, after about 7 min Mg-i(2+) returned to normal levels. This observation indicates that intracellular regulation of Mg-i(2+) is slow but operational at even very small changes of Mg-i(2+) suggesting that Mg-i(2+) levels are regulated within a very narrow band in order to guarantee its multifaceted intracellular biological activity.
Find related publications in this database (Keywords): magnesium; myocardial; ion-selective microelectrocle; acidification