Effects of idebenone on the intracellular water and dry mass content as well as of the intracellular monovalent ion concentrations of brain cortical cells of SHRsp rats as revealed by X-ray microanalysis

The cerebral cortex of ten male SHRsp rats kept in conventional housing conditions were studied. Starting from the age of 3 months, five animals received placebo (5% gum arabic solution) and five other rats received 50 mg/kg idebenone suspended in the gum arabic, through a gastric tube for 4 weeks (except Sundays). During the last 2 weeks of treatment, 0.9% NaCl was added to the drinking water. Several completely untreated SHRsp rats of various ages were also involved in these studies. Blood pressure was measured weekly on the tail by means of an appropriate instrument. Serious hypertension was observed already by the end of the second week of treatment, displaying values of 250-260 mm Hg and increased further by about 20 mm Hg during the last 2 weeks of treatment. Intracellular water, dry mass and monovalent electrolyte concentrations were measured by means of a bulk specimen X-ray microanalytic method. The brain cells contained 77±1% water and 23% dry mass by weight in both placebo and verum-treated groups. The intracellular Na⁺ content of all the male SHRsp rats was found to be significantly higher (180-200%) in the brain cells, whereas K⁺ content increased only moderately, when expressed as percent of the intracellular dry mass. Idebenone treatment, however, lowered the intracellular Na⁺ content of the brain cells to a significant extent (about 20%), i.e., it improved the Na^- tolerance of the SHRsp rats, but did not alter the blood pressure.