Abstract
INTRODUCTION: Adenosine 5'-triphosphate (ATP) is a ubiquitous cellular energy source. We evaluated the effect of ATP and its analogues on nonadrenergic and noncholinergic relaxation in precontracted human corpus cavernosal smooth muscle (HCCSM). METHODS: We obtained specimens of human corpus cavernosum (HCC) from patients undergoing penile prosthesis surgery (patient age 46-70 yr, n = 17) with prior approval from the local institutional review board. Isolated HCC strips were placed in organ baths containing Krebs solution and functional experiments were conducted. Immunohistochemical localization studies were performed to establish the presence of purinergic P2X1, P2Y1 and P2Y2 receptors in HCC. RESULTS: The amplitude of relaxation induced by electrical-field stimulation (EFS) on HCC was significantly increased after exposure to ATP (P2X and P2Y agonists), 2-MeSATP (P2Y1 agonist), and uridine 5' triphosphate (P2Y2 agonist), but not alpha,beta-methylene ATP (P2X1 agonist). The P2X1 antagonist pyridoxal-5'-phosphate-6-azophenyl-2', 4'-disulfonate, and the nonspecific P2Y antagonist, reactive blue 2, did not inhibit the potentiated response of EFS on HCC. Although immunoreactivity for both P2Y1 and P2Y2 receptors was localized abundantly in HCC, there was only low-level immunostaining for the P2X1 receptor. CONCLUSION: These data demonstrate that nerve-mediated relaxation of HCCSM strips precontracted with phenylephrine in organ bath preparations is amplified by stimulating purinergic P2Y1 and P2Y2 receptors. Although nucleotides are important regulators of HCCSM tone, these observations suggest an independent purinergic relaxing mechanism in the HCC, separate from the better known nitrergic system.