Role of hydrogen sulfide production in inhibitory action of L-cysteine on isolated porcine irides.

Purpose: To investigate the direct pharmacological actions of L-cysteine, a substrate for the production of H2S, on isolated porcine irides in the presence of tone induced by muscarinic receptor stimulation. Furthermore, we examined the underlying mechanism of action of L-cysteine in this smooth muscle.Methods: Isolated porcine iris muscle strips were set up in organ baths containing oxygenated Krebs buffer solution at 37°C. Longitudinal isometric tension was recorded via a grass FT03 Force-Displacement Transducer and analyzed using the PolyView computer software. The relaxant action of L-cysteine on carbachol-induced tone was studied in the absence and presence of inhibitors of enzymes of the biosynthetic pathways for H2S, and prostanoids. In addition, we also examined the effect of ATP-sensitive K+ (KATP) channel antagonist, glibenclamide on relaxations induced by L-cysteine.Results: L-cysteine (30 nM–1 mM) evoked concentration-dependent relaxations of carbachol-induced tone in isolated porcine irides, ...