Abstract
1. The exchange of cellular Mg with external 28Mg in the rat left ventricle was measured in vivo and, under conditions approximating a steady state, in an isolated, working rat heart perfused and contracting at 36-38° C.
2. About 98% of cellular Mg exchanged at a single rate.
3. The rate of exchange in vivo was the same as that observed in independent in vitro measurements of the influx and efflux at the physiological external Mg2+ concentration of 0·56 mM. The rate was 0·15 ± 0·02 m-mole/(kg dry ventricle.min) or 0·21 ± 0·02 p-mole/(cm2.sec).
4. In the perfused heart the dependence of the influx on the external Mg concentration was hyperbolic with an apparent Vmax of 0·31 ± 0·04 m-moles/(kg dry weight.min) and an apparent Km of 0·57 ± 0·08 mM.
5. The Mg efflux into a solution containing 2·8 mM-Mg was markedly faster than that into a Mg-free solution.
6. These results are interpreted as consistent with a carrier-mediated transport of Mg across the plasma membrane.
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Selected References
These references are in PubMed. This may not be the complete list of references from this article.
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