Importance of decreased intracellular phosphate and magnesium concentrations and reduced ATPase activities in spontaneously hypertensive rats.
A decrease in total magnesium content is not a direct proof of a decreased magnesium ion concentration. It could reflect a phosphate alteration or an ATP metabolism disorder. Plasma phosphate levels are lower in spontaneously hypertensive rats (SHRs) than in Wistar-Kyoto (WKY) rats, and defects in membrane regulation or mitochondrial ATP synthase occur. Only sparse data exist concerning cellular magnesium and phosphate concentrations in hypertensive cells. In aortic smooth muscle cells from 10 SHRs of the Münster strain and 10 age-matched normotensive WKY rats, the intracellular phosphate and magnesium content was measured by electron probe X-ray microanalysis (Camscan CS 24 apparatus, Cambridge, U.K.). The Mg++ content was 0.90+/-0.15 g/kg dry weight in SHRs versus 1.15+/-0.10 g/kg dry weight in WKY rats (p<0.05). Vascular smooth muscle phosphate content was 23.6+/-0.79 g/kg dry weight in WKY rats versus 15.81+/-1.22 g/kg dryweight in SHRs (p<0.01). In seven animals, erythrocytic ATP content was 180.2+/-102 in SHRs vs. 432+/-72 micromol/L cells in WKY rats (p< 0.01). The Na+/K+-ATPase activity was significantly decreased in hypertensive animals as compared to controls (6.49+/-2.3 vs. 12.64+/-2.9 nmol inorganic phosphate/mg protein/min (p< 0.01)). Aortic smooth muscle cells from SHRs are characterized by markedly lowered cellular phosphate and magnesium concentrations and an altered ATP metabolism, possibly due to a membrane defect or a magnesium deficit in hypertensive cells.
Kisters
K
K
Medical University Policlinic, Münster, Germany.
Krefting
E R
ER
Hausberg
M
M
Kohnert
K D
KD
Honig
A
A
Bettin
D
D
D000255:Adenosine Triphosphate / Q000032:analysis; D000818:Animals; D001011:Aorta; D004577:Electron Probe Microanalysis; D006973:Hypertension / Q000378:metabolism*; D008274:Magnesium / Q000032:analysis*; D009131:Muscle, Smooth, Vascular / Q000737:chemistry* / Q000201:enzymology; D010710:Phosphates / Q000032:analysis*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D010710:Phosphates; D000255:Adenosine Triphosphate; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium