Inhibition by sildenafil of contractility of isolated non‑pregnant human myometrium

Objective: To investigate the ability of sildenafil to inhibit the contractility of isolated non pregnant human myometrium. Materials and Methods: The inhibitory effect of three concentrations (3, 10, and 30 µM) of sildenafil on 55 mM KCl‑induced contractility of isolated non‑pregnant human myometrium was studied. The ability of the guanylyl cyclase inhibitor ODQ (10 µM), the adenylyl cyclase inhibitor MDL‑12,330A (10 µM), the non‑specific potassium channel blocker TEA (2 mM), and the calcium‑sensitive potassium (BKCa) channel blocker iberiotoxin (100 nM) to reverse the inhibition of 10 µM sildenafil on KCl‑induced myometrial contractility was also studied. Results: Sildenafil produced a concentration‑dependent inhibition of KCl‑induced myometrial contractility that was statistically significant at all three concentrations of sildenafil used. The inhibition by 10 µM sildenafil of KCl‑induced myometrial contractility was not reversed by the concurrent administration of ODQ or MDL‑12,330A. The inhibition of 10 µM sildenafil of myometrial contractility was partially reversed by concurrent administration of TEA and totally and significantly reversed by the concurrent administration of iberiotoxin. Conclusions: These results suggest that sildenafil inhibits the contractility of isolated non‑pregnant human myometrium. The results suggest that sildenafil does so by opening BKCa channels.