Assessment of intracellular sodium and calcium in essential hypertension during diuretic treatment

In 87 essential hypertensive patients, torasemide (1- isopropyl-3-([4-(3-methyl-phenylalmino)pyridine]-3-sulfonyl)urea), a new long-acting high-ceiling diuretic, was applied for 6 months in order to assess its effects on blood pressure and intracellular electrolytes. In a randomized trial 42 patients received 2.5 mg and 45 patients 5 mg torasemide once daily. In all patients, diastolic blood pressure was greater than 100 mm Hg before treatment. Blood pressure normalisation (diastolic blood pressure greater than or equal to 90 mmHg) was observed in 21 out of 42 patients receiving 2.5 mg torasemide daily and in 26 out of 42 patients with 5 mg torasemide throughout the study. In both groups doubling of the dosage was performed in these patients who had an insufficient blood pressure control after 4 weeks. In the majority of these non-responders blood pressure normalisation was achieved during the higher dosages. In the total group of patients there was an elevation of the intracellular sodium and a decrease of the intracellular calcium, measured with the ion-selective electrode in red blood cells. It could be shown that the decrease in blood pressure induced by torasemide was accompanied by a decrease of intracellular Ca2+, thus supporting the hypothesis that intracellular free Ca2+ is an important regulator of vascular tone in essential hypertension.