Evidence of relaxant effect of omeprazole in rabbit corpus cavernosum in vitro

The present experiments were designed to investigate the effects of omepraz ole, a H+-K+ ATPase inhibitor, on corporal smooth muscle tone in vitro. All spontaneous contractile activity in the corpus cavernosum was blocked foll owing omeprazole (0.1 mM-1 mM) administration. However atropine (1 mu M), N -w-nitro L-arginine methyl ester (L-NAME, 30 mu M) or indomethacin (10 mu M ) did not affect the spontaneous contraction. Omeprazole (10 mu M-1 mM) con centration-dependently induced relaxation in corporal smooth muscle precont racted with 10 mu M phenylephrine or 80 mM KCI. Pretreatment of corporal ti ssue with L-NAME (30 mu M) indomethacin (10 mu M), ammonium chloride (7.5 m M), sodium acetate (7.5 mM), tetraethyl ammonium chloride (0.5 mM) or glibe nclamide (1 mu M) had no effect on the omeprazole induced relaxant response s. Nimodipine, an L-type Ca++ channel blocker relaxed corporal strips preco ntracted with 80 mM KCI. Collectively, these results indicate that the inhi bition of spontaneous Contraction and the relaxation of precontracted corpo ral smooth muscle by omeprazole is probably mediated by the blockade of cal cium channels. Further work is needed to determine the cellular mechanism(s ) of action by which omeprazole acts on corpus cavernosum smooth muscle.