Altered monocyte calcium dynamics in sepsis

This study was designed to evaluate monocyte calcium concentration and mobilization in normal and septic surgical patients.

Monocytes were isolated from 15 "septic" surgical patients, washed, and loaded with the fluorescent calcium chelator, FURA-2. Monocytes from 20 normal volunteers served as controls. Intracellular calcium concentration ([Ca2+]i) was measured by means of fluorescent spectrophotometry before, during, and after stimulation with concanavalin A. Differences were evaluated for statistical significance by analysis of variance. The study was repeated using normal monocytes preincubated in "septic" serum and "septic" monocytes preincubated in normal serum. Additional paired whole blood specimens were obtained from the control group and were incubated with Escherichia coli endotoxin. Monocytes were then isolated and evaluated as described.

Sepsis was associated with significantly low resting monocyte calcium concentrations. Although concanavalin A stimulation resulted in marked calcium mobilization in both normal and septic cells, final cellular calcium concentration was significantly lower in the stimulated "septic" monocytes. Similar alterations were seen in normal cells incubated with septic serum, but could not be reproduced by incubation with endotoxin. This deficiency could not be corrected in septic cells incubated in normal serum.

Sepsis is associated with a significant alteration of monocyte calcium dynamics in both resting and stimulated cells. These changes appear to be modulated by a serum factor other than endotoxin.