Properties of a Cl- current activated by cell swelling in rabbit portal vein vascular smooth muscle cells.

In rabbit portal vein smooth muscle cells, application of a hypotonic external solution caused cell swelling and evoked an outwardly rectifying Cl- current. The hypotonicity-activated current was markedly reduced by the anti-estrogen tamoxifen (10 microM) and was inhibited by DIDS in a voltage-dependent manner [the concentration required to inhibit the current by 50% (IC50) at -50 and +100 mV was 21 and 5 microM DIDS, respectively]. Indanyloxyacetic acid 94 (IAA-94) and niflumic acid also inhibited the hypotonicity-activated current, with 50% inhibition produced at concentrations of approximately 200 and 100 microM, respectively. In isotonic conditions, application of tamoxifen and DIDS to cells decreased the holding current due to the inhibition of a resting conductance that was outwardly rectifying and reversed at the Cl- equilibrium potential. These data show that rabbit portal vein myocytes have a resting Cl- conductance that is enhanced by cell swelling; its possible physiological role is discussed.