1. Cytosolic free calcium concentrations ([a2+]i) were measured in resting and chemotactic peptide-activated neutrophils from eight patients with Bartter's syndrome and compared with levels determined in neutrophils isolated from healthy controls.
2. [Ca2+]i was measured with the intracellular trappable fluorescent indicator Quin2. The synthetic tripeptide formylmethionyl-leucyl-phenylalanine (fMet-Leu-Phe) was used as a stimulant.
3. No difference was found in resting [Ca2+]i between neutrophils from normal controls and those from patients with Bartter's syndrome.
4. On the contrary increases in [Ca2+]i stimulated by fMet-Leu-Phe concentrations higher than 10−8 mol/l were significantly less in neutrophils from patients with Bartter's syndrome.
5. It is suggested that neutrophils from patients affected by Bartter's syndrome exhibit an intrinsic anomaly in the mechanism responsible for intracellular Ca2+ mobilization.