Measurement of intracellular chloride in guinea‐pig vas deferens by ion analysis, 36chloride and micro‐electrodes

Abstract

1. Cl‐sensitive micro‐electrodes were used to measure the intracellular Cl activity (aCli) in smooth muscle cells of the guinea‐pig vas deferens. The values obtained were compared with those of intracellular Cl (Cli) found by both ion analysis and 36Cl efflux. 2. Various combinations of filling solution for recording membrane potential (Em), and type of micro‐electrode were tested. The most successful, which allowed continuous recording of aCli for several hours, was a double‐barrelled electrode using the reference liquid ion exchanger (RLIE; Thomas & Cohen, 1981). However, aCli measured both by simultaneous impalements of separate cells with Cl‐sensitive and conventional micro‐electrodes, and by double‐barrelled micro‐electrodes, was about 42 mM in normal Krebs solution. This is five times higher than the value from a passive distribution. ECl was about ‐24 mV, more than 40 mV positive to Em. 3. On complete removal of extracellular Cl (Clo), aCli fell to an apparent level of about 3 mM. If this represents interference from other anions, the maximum error in ECl measured in normal Krebs solution is 2·5 mV. Replacement of Clo caused a rapid increase in aCli. This must be caused by an active transport of Cl− ions into the cell against their electrochemical gradient. 4. The stabilized values of aCli measured at different levels of Clo agree surprisingly well with aCli estimated from ion analysis and 36Cl efflux, assuming that the intracellular activity coefficient was the same as measured in the normal Krebs solution. The relationship of aCli to Clo was hyperbolic. 5. It is concluded that Cl‐sensitive micro‐electrodes accurately measure aCli in smooth muscle cells. The remarkable agreement between the direct and indirect methods of measuring Cli suggests that Cl− ions are not bound to a significant extent and that the compartment seen by the micro‐electrodes is probably representative of the whole cell. © 1982 The Physiological Society