Ion channels in the basolateral membrane of intralobular duct cells of mouse mandibular glands

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Abstract
We have used single-channel patch-clamp techniques to study the ion channels in the basolateral membranes of intralobular duct cells from the mouse mandibular gland. In 39% of cell-attached patches, we observed a K+ channel that had an inwardly rectifying current/voltage (I/V) relation with a maximum slope conductance of 123±9 pS (n=12) and a zero current potential of +49.4±3.4 mV (n=5) relative to the resting cell potential. The selectivity sequence of this channel, as estimated by zero current potential measurements, was: K+ (1) > Rb+ (0.38) > NH 4 + (+ ( Na+ ( Rb+ ( NH 4 + ( Na+ (n=6) and was blocked by the non-selective cation channel blocker, flufenamate (10 μmol/l). A fourth channel type, observed only in 5% of patches was a Cl− channel with a slope conductance of 40 pS and a linearI/V relation. The K+ channels observed in this study seem likely to underlie the K+ conductance described in the basolateral membrane of extralobular ducts by in vitro perfusion studies. Our finding that they are inwardly rectifying suggests that they may not be the sole route of K+ transport across the basolateral membrane.