Measurement of intercellular electrical coupling in guinea-pig detrusor smooth muscle

Purpose: The electrical impedance of detrusor smooth muscle strips to alternating current has been measured to calculate the resistance of the intracellular pathway, in particular gap junction resistance. Values have been compared with myocardium, which is electrically well-coupled. Materials and Methods: Alternating current was passed along the intracellular pathway of muscle strips by creating a high extracellular resistance around the preparation. The data were analyzed in terms of an equivalent circuit consisting of an intracellular and extracellular pathway. Results: Intracellular resistance was divided into two series components, a cytoplasmic resistance and a gap junction resistance. Detrusor intracellular resistance was about three times that of myocardium. The greater value was attributed to a larger gap-junction resistance. Superfusion of detrusor strips with an isosmotic solution of 50% sucrose, 50% Tyrode's increased both cytoplasm and gap junction resistances. Conclusions: Gap-junction resistance is larger in detrusor compared with myocardium. However, significant electrical current can still pass between adjacent detrusor cells. Calculation of the space constant however shows that functionally detrusor is electrically well-coupled because of the high membrane resistance. The functional consequences of these findings are discussed.