The characteristics of hemolysis produced by streptolysin S (SLS) were investigated in rabbit erythrocytes. Treatment of erythrocytes with SLS at various temperatures prior to incubation at 37 C revealed an initial temperature-dependent interaction between toxin and the cells. No subsequent hemolysis occurred when erythrocytes were exposed to SLS at 0 to 10 C; exposure to toxin at temperatures above 10 C gradually increased the amount of hemolysis that occurred at 37 C. Very little binding of toxin to erythrocytes or their ghosts, as detected by a decrease of hemolytic activity from toxin preparations, could be demonstrated at any temperature. The release ofhemoglobin after the temperature-dependent process occur at virtually the same rate at 0, 22, or 37 C. The loss of intracellular rubidium-86 (Rb) and hemoglobin from SLS-treated erythrocytes was studied. Rb+ release significantly preceded the escape of hemoglobin, suggesting that colloid-osmotic processes play a role in SLS hemolysis.

The purpose of this study was to examine regulatory volume decrease (RVD) in Atlantic salmon red blood cells (RBCs). Osmotic fragility was determined optically, mean cell volume was measured electronically, and changes in intracellular Ca(2+) concentration were visualized using fluorescence microscopy and fluo-4-AM. Cells displayed an increase in osmotic fragility and an inhibition of volume recovery following hypotonic shock when they were exposed to a high taurine Ringer or when placed in a high K(+) medium. Interestingly, RVD in cells from fish collected during the summer depended more on taurine efflux, whereas fall cells relied more on the loss of K(+). In addition, RVD in fall cells was prevented with the K(+) channel inhibitor quinine, whereas the ionophore gramicidin decreased osmotic fragility and potentiated volume recovery. Further, hypotonic shock (0.5X Ringer) for both summer and fall cells caused an increase in cytosolic Ca(2+), which resulted from influx of this ion because it was not observed when extracellular Ca(2+) was chelated with EGTA (10 nM free Ca(2+)). Cells exposed to a low Ca(2+) hypotonic Ringer also had a greater osmotic fragility and failed to recover from hypotonic swelling. Finally, inhibition of phospholipase A(2) with ONO-RS-082 blocked volume recovery. In conclusion, Atlantic salmon RBCs displayed volume decrease in response to hypotonic shock, which depended on a swelling-induced influx of Ca(2+) and an increase in the efflux of K(+) and taurine.