Functional Studies of Synthetic Gramicidin Hybrid Ion Channels in CHO Cells

Abstract

The function of a gramicidin hybrid ion channel in living Chinese hamster ovary (CHO) cells was investigated by the patch clamp method. The synthetic ion channel 1 consists of two cyclohexyl ether amino acids that link two minigramicidin strands. With 1 at a concentration of 1.0 μM, an increase in the whole‐cell membrane conductance was observed after 1.37 min. The conductance showed larger currents when Cs⁺ was used as charge carrier than when Na⁺ and K⁺ were used. In single‐channel recordings with Cs⁺ as charge carrier, the substance showed comparable single‐channel amplitudes in the membrane of living cells and artificial black lipid bilayers. In addition to functioning as a cation channel, compound 1 appeared to be a water channel. Exposure of the CHO cells to an extracellular hypoosmotic solution did not substantially change the cell volume. Extracellular hypoosmotic conditions in the presence of 1 increased the cell size to 146.5 % that of the control. Thus, the synthetic hybrid channel 1 can function as a cation channel with some Cs⁺ specificity, and as a water channel in CHO cells.