Human red blood cell hemolysate is a potent mitogen for renal tubular epithelial cells

Conditions associated with intravascular hemolysis are often complicated by acute renal failure which is characterized by renal vasoconstriction and tubular injury. However, the effects of human red blood cell (RBC) hemolysate on renal tubular epithelial cell function have not been well characterized. We therefore measured the effect of distilled water-lysed human RBCs on cultured LLC-PK1 cell function. We found that human RBC hemolysate produced a marked effect to promote LLC-PK1 3H-thymidine uptake that was several-fold higher than that produced by maximal concentrations of several known growth factors. Partial purification of human RBC hemolysate by sequential centrifugation and passage over a column that removes low molecular weight substances each significantly reduced, but did not totally eliminate, the effect of human RBC hemolysate to promote 3H-thymidine uptake. Exposure of LLC-PK1 cells to horse myoglobin also stimulated 3H-thymidine incorporation in LLC-PK1 cells. A reducing agent (ascorbic acid) decreased the effect of horse myoglobin and of human RBC hemolysate to promote LLC-PK1 mitogenesis. Ascorbic acid also decreased the methemoglobin content of human RBC hemolysate. The effect of human RBC hemolysate to increase LLC-PK1 incorporation of 3H-thymidine could also be significantly decreased by either of two inhibitors of tyrosine kinase. These results suggest that there are several components of human RBC hemolysate that promote LLC-PK1 3H-thymidine incorporation. One of these components appears to be methemoglobin that exerts its effect via a tyrosine kinase signal transduction pathway.