Microelectrode measurement of intracellular chloride activity in smooth muscle cells of guinea-pig ureter

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Abstract
The intracellular Cl activity (a Cl i ) of smooth muscle cells in the guinea-pig ureter was measured using double-barrelled Cl-sensitive microelectrodes. The meana Cl i in normal Krebs solution was 51.1 mM, equivalent to anE Cl of −18.6 mV, with a meanE m of −48.7 mV. Thusa Cl i was three times higher than predicted from a passive distribution.a Cl i exceeded the extracellular activity by nearly 10 mM in 10%-Cl solution. Complete removal of extracellular Cl (Cl0) caused a decline ina Cl i to an apparent level of 3.3 mM with a mean time constant of 6.7 min. Cl ions were reaccumulated against their electrochemical gradient on readmission of Cl0 with a mean time constant of 6.6 min. Both the reaccumulation and loss of Cl ions on changing Cl0 were slowed about three-fold by the nominal absence of CO2 and HCO3 and over ten-fold by the presence of the anion exchange inhibitor DIDS. It is therefore concluded that most of the transmembrane Cl movements are mediated by a reversible anion exchange carrier and thatP Cl is very low. These results are similar to those obtained in vas deferens and may be a general feature of smooth muscle cells.