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Effect of mersalyl on mitochondrial Mg++ flux
Abstract:
The mercurial mersalyl has little effect either on rapid Mg++ binding by isolated rat liver mitochondria or on the total Mg++ content of these organelles measured after 0.75 min of incubation at 20 degrees C. The data do not support the previous suggestion that the increased permeability to K+ of mitochondria treated with mersalyl results from release of endogenous Mg++. An increased pH-dependence of unidirectional Mg++ flux into respiring rat liver mitochondria is suggested to arise indirectly from inhibition by mersalyl of pH shifts associated with exchanges of endogenous phosphate. In addition, mersalyl appears to have a stimulatory effect on Mg++ influx. Mersalyl also increases the average rate of unidirectional efflux of endogenous Mg++. The stimulatory effects of mersalyl on Mg++ flux are similar to, although quantitatively less than, the previously reported effects of mersalyl on mitochondrial K+ flux.
Insights
Mersalyl, a mercurial compound, minimally impacts magnesium binding in rat liver mitochondria. It does not cause magnesium release, contrary to prior suggestions, but does affect magnesium flux.
Area of Science:
- Biochemistry
- Mitochondrial Physiology
- Cellular Transport
Background:
- Mitochondria play a crucial role in cellular energy metabolism and ion homeostasis.
- Magnesium (Mg++) is essential for mitochondrial function and is actively transported across the inner mitochondrial membrane.
- Mersalyl, a mercurial compound, has been previously suggested to affect mitochondrial permeability.
Purpose of the Study:
- To investigate the effect of mersalyl on rapid Mg++ binding and total Mg++ content in isolated rat liver mitochondria.
- To examine whether mersalyl-induced changes in mitochondrial permeability to potassium (K+) are related to the release of endogenous Mg++.
- To elucidate the mechanisms by which mersalyl influences Mg++ flux across the mitochondrial membrane.
Main Methods:
- Incubation of isolated rat liver mitochondria with mersalyl at 20°C for 0.75 minutes.
- Measurement of rapid Mg++ binding and total Mg++ content.
- Assessment of unidirectional Mg++ flux (influx and efflux) in respiring mitochondria.
- Analysis of pH dependence of Mg++ flux.
Main Results:
- Mersalyl showed minimal effect on rapid Mg++ binding and total Mg++ content in mitochondria.
- Data did not support the hypothesis that mersalyl-induced K+ permeability changes result from endogenous Mg++ release.
- Mersalyl increased the pH-dependence of Mg++ influx, likely due to indirect inhibition of pH shifts from phosphate exchanges.
- Mersalyl demonstrated a stimulatory effect on both Mg++ influx and the rate of endogenous Mg++ efflux.
Conclusions:
- Mersalyl does not significantly alter Mg++ binding or content in rat liver mitochondria.
- The mechanism of mersalyl's effect on mitochondrial permeability is not mediated by Mg++ release.
- Mersalyl influences Mg++ flux by affecting pH-dependent transport and increasing both influx and efflux rates, similar to its effects on K+ flux.