Pharmacological characterization of the isolated canine prostate

Purpose: The goal of the present study was to characterize the responses of the isolated normal canine prostate to various contracting and relaxing stimuli to determine which pharmacological agents may have utility against the dynamic component of benign prostatic hyperplasia (BPH). Materials and Methods: Isometric force development was measured in isolated strips of prostate tissue. Results: The alpha-adrenergic agonists were the most efficacious stimulants tested (phenylephrine EC(50) = 2.1 mu M.). Endothelin-1, acting primarily via ET(A) receptors, was more potent (EC(50) = 27 nM.) but less efficacious. Histamine (EC(50) = 14.7 mu M.), serotonin (EC(50) = 0.12 mu M.), carbachol (EC(50) = 5.9 mu M.) and KCl (EC(50) = 48.8 mM.) were also less efficacious than phenylephrine. Nifedipine was a potent (IC50 = 28 nM.) and efficacious (74% inhibition) inhibitor of phenylephrine-induced force. Potassium channel activator drugs were also efficacious relaxants, producing approximately 80% inhibition of force; rank order of potency was P1075 > cromakalim > diazoxide. Sodium nitroprusside was a weak relaxant, producing only similar to 40% relaxation at a concentration of 100 mu M. Both isoproterenol and forskolin were effective relaxants (75 to 90% relaxation). Conclusions: We conclude that potassium channel activators, adenylate cyclase stimulators, or endothelin antagonists may have utility against the dynamic component of outflow obstruction secondary to BPH.