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Changes in phospholipid composition and calcium flux in LLC-PK cells cultured at low magnesium concentrations
M M Mahfouz1, T L Smith, F A Kummerow
1Burnsides Research Laboratory, University of Illinois, Urbana.
Abstract:
Monolayers of porcine kidney cells (LLC-PK) were grown in a series of Nu-Serum-supplemented media containing different Mg(2+) concentrations (480, 250, 25, 6.3 or 2.6 microM) to study the effect of Mg(2+) depletion on cellular phospholipid changes and the consequent effect on the membrane permeability to Ca(2+). Cells grown on 6.3 or 2.6 microM Mg(2+) showed a decrease in PE, PS, Sph, PI and an increase of PC. These changes were attributed mainly to the decreased rate of Sph synthesis through the transfer of phosphocholine from PC to ceramide, or due to the increase of PE N-methylation as found in Mg(2+)-deficient cells. The (45)Ca uptake was increased in cells grown on 25.0 microM Mg(2+), while it was decreased in cells grown on 6.3 or 2.6 microM Mg(2+). These changes in Ca(2+) uptake were related to changes of cellular phospholipids and fatty acids which affect adenylate cyclase activity in the membrane, as well as the membrane fluidity.
Insights
Magnesium (Mg2+) depletion in kidney cells alters cell membrane phospholipids, affecting calcium (Ca2+) permeability. Lower Mg2+ levels decrease specific phospholipids and Ca2+ uptake, impacting cell function.
Area of Science:
- Cell Biology
- Biochemistry
- Membrane Physiology
Background:
- Cellular magnesium (Mg2+) is crucial for various cellular processes.
- Mg2+ levels can influence cell membrane composition and function.
- Understanding Mg2+ effects on phospholipids and ion transport is vital for cell health.
Purpose of the Study:
- To investigate the impact of varying Mg2+ concentrations on porcine kidney cell (LLC-PK) phospholipid profiles.
- To determine how Mg2+-induced phospholipid changes affect membrane permeability to calcium (Ca2+).
Main Methods:
- LLC-PK cells were cultured in media with diverse Mg2+ concentrations (2.6–480 microM).
- Cellular phospholipid composition (PE, PS, Sph, PI, PC) was analyzed.
- Radiolabeled calcium-45 ((45)Ca) uptake was measured to assess membrane permeability.
Main Results:
- Mg2+ depletion (6.3 or 2.6 microM) led to decreased phosphatidylethanolamine (PE), phosphatidylserine (PS), sphingomyelin (Sph), and phosphatidylinositol (PI).
- Increased phosphatidylcholine (PC) was observed under Mg2+ deficiency.
- Calcium (Ca2+) uptake was elevated at 25.0 microM Mg2+ but reduced at 6.3 or 2.6 microM Mg2+.
- Phospholipid and fatty acid alterations correlated with changes in adenylate cyclase activity and membrane fluidity.
Conclusions:
- Mg2+ deficiency significantly alters kidney cell phospholipid metabolism, particularly Sph synthesis and PE N-methylation.
- Changes in membrane phospholipid composition directly influence Ca2+ permeability.
- These findings highlight the critical role of Mg2+ in maintaining cell membrane integrity and ion homeostasis.