Intraplatelet calcium levels in patients with acute renal failure before and after the administration of loop diuretics.
BACKGROUND
Intracellular calcium [Ca](i) has been found to be elevated in hypoxic cells in vitro and in erythrocytes and lymphocytes from patients who are septic. Loop diuretics decrease [Ca](i) in platelets from patients with hypertension and in red blood cells from normal volunteers. We report the results of a study designed to measure [Ca](i) in platelets from patients with acute renal failure (ARF) before and after the administration of loop diuretics.


METHODS
Sixteen healthy adults and seven patients with ARF were enrolled into the study. Intraplatelet calcium was measured using a fluorescent probe (quin2). Patients with ARF all received intravenous (i.v.) dopamine, 2 microg/kg body weight, and 20% mannitol, 100 ml every 6 h and, in double-blind manner, either torasemide, frusemide, or placebo, 3 mg/kg body weight i.v. every 6 h. Data from subjects given either frusemide or torasemide have been considered together and termed the diuretic group.


RESULTS
Basal levels of [Ca](i) in platelets from patients with ARF were significantly higher than in controls (126.9 +/-3 5.7 nmol/l vs 85.7 +/- 22.2 nmol/l, P = 0.02), but were not affected by the administration of loop diuretic (126.9 +/- 35.7 nmol/l vs 165.9 +/- 49.7 nmol/l, P = 0.09, pre- vs post-diuretic).


CONCLUSIONS
Intraplatelet calcium is raised in patients with ARF. Loop diuretics have no significant effect on intraplatelet calcium in these patients.