Cholesterol transfer from rat, human and sheep erythrocytes

1. The spontaneous transfer of cholesterol out of sheep, rat and human erythrocyte membranes was measured. 2. The rates of cholesterol transfer did not correlate with the very different levels of sphingomyelin in the membranes. 3. Cholesterol transferred at similar rates out of vesicles made of lipids extracted from the three types of erythrocyte. 4. The results are discussed in relation to the proposal that cholesterol and sphingomyelin are closely associated in cell surface membranes.