Short-term reduction in dietary intake of magnesium causes deficits in brain intracellular free Mg2+ and [H+]i but not high-energy phosphates as observed by in vivo 31P-NMR.
31P-NMR spectroscopic studies were performed in vivo on brains of rats fed 30-35% normal dietary Mg intake for 6 weeks. Within 2 weeks of the moderately restricted Mg diet serum Mg fell 50%, and brain intracellular free [Mg2+]i fell 15%; within 3 weeks of restricted diet, brain [Mg2+]i fell 40% and remained at this level for the additional 3 weeks. Intracellular pH (pH[i]) progressively rose in a reciprocal manner for 4 weeks. At no interval of time did brain phosphocreatine (PCr), [ATP], or inorganic phosphate change despite the fall in brain [Mg2+]i, brain pH(i) and serum Mg. The Mg-deficiency-induced cytosolic loss of protons (resulting in an alkaline cytosol) could be a compensatory mechanism to stabilize [PCr], [ATP] and [ADP] levels via creatine kinase, thus maintaining cytosolic phosphorylation potential. The rise in pH(i) associated with Mg-deficiency would also account for increased cerebral vascular muscle contractility under these conditions. Lastly, these studies indicate that brain [Mg2+]i may change without a concomitant change in cell [ATP], and that brain [Mg2+]i may be a useful marker for total body Mg2+ status.
Altura
B M
BM
Department of Physiology, State University of New York, Health Science Center at Brooklyn, 11203, USA.
Gebrewold
A
A
Zhang
A
A
Altura
B T
BT
Gupta
R K
RK
D000227:Adenine Nucleotides / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000098:blood supply / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000008:administration & dosage* / Q000097:blood; D008275:Magnesium Deficiency / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D000227:Adenine Nucleotides; D010725:Phosphocreatine; D000255:Adenosine Triphosphate; D008274:Magnesium