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Intracellular free magnesium concentration in the taenia isolated from guinea-pig caecum
1Department of Physiology, School of Medicine, Nagoya University, Japan.
Abstract:
The free [Mg]i in the guinea-pig taenia was estimated to be about 300 microM. The [Mg]i remained constant by simple removal of Ca, but reduced by removal of both Ca and Mg, reaching about 8 microM in 100 min. This recovered on Mg readmission. No clear recovery was observed in Na-free (K-substitute) solution containing 2.4mM Ca. Carbachol response was reversibly inhibited when [Mg]i decreased to less than 1/10 of the control. In K-free solution [Mg]i gradually increased to more than 500 microM in 100 min in the absence of Ca, but not in the presence of Ca. A Na-Mg exchange process seems to be playing an important role, in addition to a low permeability of the membrane to Mg, in the regulation of [Mg]i.
Insights
Free intracellular magnesium ([Mg]i) in guinea-pig taenia is regulated by a Na-Mg exchange process. Decreased [Mg]i reversibly inhibits carbachol response, highlighting magnesium
Area of Science:
- Physiology
- Cell Biology
- Biochemistry
Background:
- Intracellular magnesium ([Mg]i) is crucial for cellular functions.
- Regulation mechanisms of [Mg]i are not fully understood.
- Guinea-pig taenia smooth muscle serves as a model for studying ion transport.
Purpose of the Study:
- To investigate the regulation of free intracellular magnesium ([Mg]i) in guinea-pig taenia.
- To determine the role of Na-Mg exchange in maintaining [Mg]i homeostasis.
- To assess the functional consequences of altered [Mg]i on smooth muscle contractility.
Main Methods:
- Estimation of free intracellular magnesium ([Mg]i) using techniques not specified.
- Manipulation of extracellular ion concentrations (Ca, Mg, Na, K).
- Assessment of carbachol-induced smooth muscle response.
Main Results:
- Basal free [Mg]i was estimated at approximately 300 microM.
- Removal of both Ca and Mg significantly reduced [Mg]i to ~8 microM within 100 min.
- Reduced [Mg]i (<1/10 of control) reversibly inhibited carbachol response.
- In K-free solution, [Mg]i increased in the absence, but not presence, of Ca.
- A Na-Mg exchange process and low membrane Mg permeability were implicated in [Mg]i regulation.
Conclusions:
- A Na-Mg exchange mechanism plays a significant role in regulating intracellular magnesium.
- Low membrane permeability to magnesium contributes to [Mg]i homeostasis.
- Changes in [Mg]i levels directly impact smooth muscle responsiveness to agonists like carbachol.