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

Purpose: The electrical impedance of detrusor smooth muscle strips to alter nating current has been measured to calculate the resistance of the intrace llular pathway, in particular gap junction resistance. Values have been com pared with myocardium, which is electrically well-coupled. Materials and Methods: Alternating current was passed along the intracellul ar pathway of muscle strips by creating a high extracellular resistance aro und the preparation. The data were analyzed in terms of an equivalent circu it 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 intracellul ar resistance was about three times that of myocardium. The greater value w as attributed to a larger gap-junction resistance. Superfusion of detrusor strips with an isosmotic solution of 50% sucrose, 50% Tyrode's increased bo th cytoplasm and gap junction resistances. Conclusions: Gap-junction resistance is larger in detrusor compared with my ocardium. However, significant electrical current can still pass between ad jacent detrusor cells. Calculation of the space constant however shows that functionally detrusor is electrically well-coupled because of the high mem brane resistance. The functional consequences of these findings are discuss ed.