Inhibition of the contractile responses of isolated human and rat bladdersby clenbuterol

Purpose: We investigated the inhibition of the contractile responses of hum an continent and unstable detrusor muscle by the beta2 agonist clenbuterol as well as the inhibition of electrical field stimulation evoked contractil e responses of isolated rat bladder muscle strips by orally administered cl enbuterol. Materials and Methods: The contractile responses of human continent and uns table detrusor muscle strips to electrical field stimulation (0.05 millisec onds, 0.5 to 80 Hz.) were measured before and after adding 10(-9) to 10(-4) M. clenbuterol in vitro. In addition, 6 rats per group were dosed orally w ith 2 mug. kg.(-1) clenbuterol daily acutely (1 dose) or chronically (1 dos e daily for 8 days), or with distilled water to serve as controls. The cont ractile response to electrical field stimulation of strips of isolated detr usor muscle was then measured. Serum clenbuterol levels were analyzed in du plicate by enzyme-linked immunosorbent assay and high performance liquid ch romatography. Results: In vitro clenbuterol significantly inhibited the electrical field stimulation evoked contractile responses of detrusor muscle strips from uns table but not continent human bladders. A significant inhibitory effect of clenbuterol on the electrical field stimulation evoked contractile response of rat detrusor muscle was observed after chronic but not acute oral dosin g (p <0.01). Serum clenbuterol levels measured by enzyme-linked immunosorbe nt assay and high performance liquid chromatography were not significantly different. Conclusions: Clenbuterol or related beta2-adrenoceptor agonists may represe nt a useful therapeutic strategy for detrusor muscle overactivity.