Polarized ion transport during migration of transformed Madin-Darby XXXX kidney cells.

@entity5 @entity3529 @entity189 @entity235
Epithelial cells lose their usual polarization during carcinogenesis. Although most @entity5 are of epithelial origin little is known about ion channels in @entity189 cells. Previously, we observed that migration of transformed Madin-Darby @entity235 kidney (MDCK-F) cells depended on oscillating @entity3529 channel activity. In the present study we examined whether periodic @entity3529 channel activity may cause changes of cell volume, and whether @entity3529 channel activity is distributed in a uniform way in MDCK-F cells. After determining the average volume of MDCK-F cells (2013+/-270 microm3; n=8) by means of atomic force microscopy we deduced volume changes by calculating the @entity3529 efflux during bursts of @entity3529 channel activity. Therefore, we measured the membrane conductance of MDCK-F cells which periodically rose by 22.3+/-2.5 nS from a resting level of 6.5+/-1.4 nS (n=12), and we measured the membrane potential which hyperpolarized in parallel from -35.4+/-1.2 mV to -71.6+/-1.8 mV (n=11). The distribution of @entity3529 channel activity was assessed by locally superfusing the front or rear end of migrating MDCK-F cells with the @entity3529 channel blocker charybdotoxin (CTX). Only exposure of the rear end to CTX inhibited migration providing evidence for "horizontal" polarization of @entity3529 channel activity in transformed MDCK-F cells. This is in contrast to the "vertical" polarization in parent MDCK cells. We propose that the asymmetrical distribution of @entity3529 channel activity is a prerequisite for migration of MDCK-F cells.
