Effect of partial outflow obstruction on rat detrusor contractility and intracellular free calcium concentration.

Partial outlet obstruction induces significant alteration in detrusor contractility. A mild obstruction can result in increased contractile force, whereas severe obstruction results in marked contractile dysfunction. The cellular mechanisms mediating these alterations in the contractile response are presently not known. In the current study, we have investigated the effect of both mild and severe partial outlet obstruction on detrusor contractility and correlated the contractile response to field stimulation, bethanechol, adenosine triphosphate (ATP), and KCl with the level of intracellular free calcium using FURA-2 fluorescence. Our results are as follows. Severe obstruction induced a significantly greater increase in bladder weight than mild obstruction. In general, mild outlet obstruction induced an increase in the contractile responses to field stimulation, bethanechol, ATP, and KCl, whereas severe outlet obstruction induced a decrease to field stimulation and ATP. In general, the stimulated increase in intracellular free calcium paralleled the contractile response. The results indicate that the alterations in the contractile response to field stimulation and pharmacological stimulation induced by partial outlet obstruction may be mediated by altered calcium translocation and intracellular release.