Decreased intracellular phosphate and magnesium concentrations in vascular smooth muscle cells from spontaneously hypertensive rats

Abstract

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 (SHR) than in Wistar-Kyoto rats (WKY), 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 SHR of the Münster strain and 10 age-matched normotensive WKY, 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 SHR versus 1.15 ± 0.10 g/kg dry weight in WKY (p < 0.05). Vascular smooth muscle phosphate content was 23.6 ± 0.79 g/kg dry weight in WKY versus 15.81 ± 1.22 g/kg dry weight in SHR (p < 0.01). Aortic smooth muscle cells from SHR are characterized by markedly lowered cellular phosphate and magnesium concentrations and an altered ATP metabolism.