Membrane lipid layers vs. polarized water dominated by fixed ions: a comparative study of the effects of three macrocyclic ionophores on the K+ permeability of frog skeletal muscle, frog ovarian eggs, and human erythrocytes.

The effects of 10(-7) M valinomycin, nonactin, and monactin on human erythrocytes, frog sartorius muscle, and frog ovarian oocytes in the presence of varying external K+ concentration were studied. The results showed essentially a consistent but relatively modest increase of the K+ permeability constant in cm/sec with all three antibiotics on human erythrocytes. No change in response to any one of the antibiotics was observed in frog muscles or in frog ovarian eggs. These results and reports of similar failure to demonstrate ionophore-mediated increase of K+ permeability in squid axon and inner membrane of the liver mitochondria led to the conclusion that lipid membrane barrier to ionic traffic may be significant in the human erythrocytes but even here one must regard the evidence as tentative. In contrast, for the majority of other cell types studied, the data indicate the primary, if not exclusive route of ion traffic, is via the nonlipid component of the cell membrane. The evidence that these nonlipid paths are the fixed charge-polarized water layer complex and that they cover much of the cell surface of many types of living cells was discussed.