Pharmacological characterization of canine bradykinin receptors in prostatic culture and in isolated prostate

Abstract

1. The objective of this study was to characterize pharmacologically bradykinin (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg, BK) receptors in the canine prostate. 2. Primary cultures of canine prostate stromal (PS) and epithelial cells (PE) were established and then characterized using cell-specific antibodies (actin, vimentin and cytokeratin). Cultured cells were assayed for BK receptors using fluorometric imaging plate reader assays. In addition, isolated strips of the canine prostate were studied for BK-induced isometric contraction. 3. PS cells were labeled only with anti-actin and -vimentin antibodies, while the anti-cytokeratin antibodies labeled only the PE cells. 4. In cultured prostate cells, the BK receptor 2 (B2)-preferring agonist BK induced mobilization of intracellular Ca 2+ in a concentration-dependent manner with potencies (log[EC 50]|PE, pEC 50) of 8.72 ± 0.12 in PS and 8.75 ± 0.06 in PE cells. In contrast, the BK receptor 1 (B1)-selective agonist [desArg 9]BK (Arg-Pro-Pro-Gly-Phe- Ser-Pro-Phe) did not elicit any significant effect (pEC 50<5) on Ca 2+ responses. 5. BK agonism (10 nM) was inhibited by HOE-140 (D-arginyl-L-arginyl-L-prolyl-trans-4-hydroxy-L-prolylglycyl-3-(2-thienyl) -L-alanyl-L-seryl-D-1,2,3,4-tetrahhydro-3-isoquinolinecarbonyl-L-(2a,3b,7ab) -octahydro-1H-indole-2-carbonyl-L-arginine), a B2-selective antagonist, with a log[IC 50] (pIC 50) of 8.11 ± 0.19 and 9.23 ± 0.20 in PS and PE cells, respectively. [des-Arg 10]HOE-140 (D-arginyl-L-arginlyl-L-prolyl-trans-4-hydroxy-L-prolylglycyl-3-(2-thienyl) -L-alanyl-L-seryl-D-1,2,3,4-tetrahydro-3-isoquinolinecarbonyl-L-(2a, 3b, 7ab)-octahydro-1H-indole-2-carbonyl), a B1-selective antagonist, displayed weak antagonism with pIC 50 values of 4.87 ± 0.23 and 6.38 ± 0.16 in PS and PE cells, respectively. 6. Isolated tissue strips of the canine prostate contracted to BK (10 μM) but not to [des-Arg 9]BK (10 μM). BK-induced contractility was attenuated by HOE-140 (1 μM). 7. In conclusion, canine prostates express functional B2 receptors, with no apparent B1 receptor subtypes.