Studies on the terminal stages of immune hemolysis. VI. Osmotic blockers of differing Stokes' radii detect complement-induced transmembrane channels of differing size.

We have previously shown that 0.1 M EDTA could be used to distinguish functionally different transmembrane channels produced during complement-(C) mediated hemolysis of E. In this paper we have studied the ability of sugars of varying Stokes' radii to prevent hemoglobin release from E intermediates whose lysis was inhibitable or not inhibitable by EDTA. On the basis of these experiments we propose that the inhibition of E transformation by high molarity EDTA occurs by virtue of the size of the EDTA molecule in solution. Studies on the effect of EDTA on red cell lysis induced by polyene antibiotics that form transmembrane channels of a defined size support this conclusion. The results of these experiments were interpreted to mean: 1) The EDTA inhibitable lesion of E has a smaller effective radius than the noninhibitable lesion; 2) the effective radius of the smallest lesion that yields a lytic site was less than 3.6 A; 3) the lesions produced in the red cell membrane by C are not uniform but vary in size depending on the C9 to SACl-8 ratio used to produce E.