Mitchell, Claire H.; (1994) Ion channels of cultured human retinal pigment epithelial cells. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

In this thesis, the patch clamp technique has been used to examine single channels of cultured human retinal epithelial (RPE) cells. Three main channel types were detected in the cell-attached recording mode. They had mean conductances of 24 pS, 59 pS and 96 pS with physiological solutions present. All three channel types were primarily permeable to potassium. Under physiological conditions the activity of all three channel types was voltage dependant, and increased as the patches were depolarized. However, all channel types had low levels of activity at the membrane potential. The activity of the 96 pS channel type was time dependent; the channel inactivated in response to depolarizing steps. This channel type was also sensitive to the concentration of calcium; when the cells were bathed in low calcium solution the channel open probability fell towards zero. The 96 pS channel is thus similar to the maxi-K channels in other epithelia. The presence of microvilli on the top surface of these cells supports a comparison to the apical membrane. Single channel recordings on fresh bovine RPE were also attempted, but most of the channel openings were obscured by a large, noisy conductance. The voltage-sensitivity of channel activity found in cultured cells suggests that these channels may provide a mechanism for integrating dynamic transport across the RPE.

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