THE ELECTROPHYSIOLOGICAL PROPERTIES OF CULTURED AND FRESHLY ISOLATED DETRUSOR SMOOTH MUSCLE CELLS

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Abstract
Purpose: We generated and characterized a convenient isolated cell model of human detrusor smooth muscle to understand mechanisms that may underlie detrusor instability and provide a suitable model to test potentially useful drugs. Materials and Methods: The electrophysiological properties of freshly isolated detrusor smooth muscle cells from human and guinea pig biopsies were compared with those undergoing cell culture to document in detail the changes that occur during primary culture and subsequent passages as well as the differences in the 2 species. Results: Resting electrical characteristics were changed in the cultured cells. Membrane potential was less negative (guinea pig −59 versus −42 mV.) and membrane resistance was less (138 versus 124.5 Ωcm.2). Regenerative action potentials were recorded in cultured and freshly isolated cells. In guinea pig cells the overall duration and initial rate of depolarization (upstroke) was slower in cultured than in freshly isolated cells, indicative of a decreased magnitude of ionic current in cultured cells. Human cells had a similar prolongation in culture but no decrease in the upstroke rate. Experiments with selective blockers indicated that depolarization is due to influx through L-type Ca2+ channels and repolarization occurred via Ca2+ dependent K+ channels in freshly isolated and cultured cells. No further changes to properties were observed in cells passaged up to 3 times from primary cultured cells. Conclusions: Cell culture qualitatively preserves the electrophysiological properties of detrusor smooth muscle cells, although there is some decrease in channel density.