31P MR spectroscopy was used to measure the signal intensity ratios of high-energy metabolites for the calculation of free cytosolic magnesium concentration [fMg2+] and pH in the calf muscles of patients with primary juvenile hypertension and of healthy controls. Surface coil and spectroscopic imaging techniques were used. In patients with hypertension, the concentrations of [fMg2+] was 788±33 mmol/l and intracellular pH was 7.05±0.02; these values were not significantly different from the results obtained in healthy controls ([fMg2+], 776±21 mmol/l and pH, 7.06±0.01). Biochemical assays of magnesium in the serum (S-Mg) and in urine (DU-Mg) confirmed this finding. Significant differences in the relative signal intensities of high-energy phosphates between patients with primary juvenile hypertension and healthy controls were observed: a) signal intensity ratios of PCr/Pi, PCr/PbATP, PDE/PbATP were increased, and b) Pi/PDe, Pi/PATP were decreased. The results were the same irrespective of whether the surface coil method or 31P spectroscopic imaging were employed., M. Hájek, D. Palyzová, M. Kořínek, D. Kurková., and Obsahuje bibliografii