Reversal by calcium of rat heart cell dysfunction induced by human sera in septic shock

Twenty human sera obtained during the first 24 hours following clinical onset of different septic shocks were evaluated for their effects on electric an mechanical activities of rat heart cell cultures. Possible antagonistic action of calcium was tested on these effects. The results showed that septic shock sera, when compared to normal sera, increased action potential duration and depressed contractility of beating cardiac cells. Addition of calcium reversed these two actions, though markedly higher concentration was needed for depressed contractility. The in vitro deleterious effects of septic shock sera on cell cultures were related neither to decrease in extracellular calcium, since total calcium level was moderately below normal values, nor to inhibition of low calcium channel, since the action potential was not suppressed in presence of K+ excess. This study suggests the involvement of humoral factors mimicking the cardiac effects of low calcium concentration. If calcium is involved in in vitro cardiac dysfunction, it could result only from a decrease of available calcium in cytosol.