PURPOSE: To investigate the direct pharmacological actions of L-cysteine, a substrate for the production of H(2)S, 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 degrees 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 H(2)S, and prostanoids. In addition, we also examined the effect of ATP-sensitive K(+) (K(ATP)) 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, reaching a maximum inhibition of 43% at 1 mM. This response was enhanced significantly (P < 0.001) in the presence of the COX inhibitor, flurbiprofen (3 microM). Additionally,in the presence of flurbiprofen, the H(2)S donors, NaHS and Na(2)S, mimicked the relaxations produced by L-cysteine, yielding IC(50) values of 5.8 microM and 180 microM, respectively. Both the inhibitor of cystathionine beta-synthase, AOA (30 microM) and the K(ATP) channel antagonist, glibenclamide (100 microM) caused significant (P < 0.001) rightward shifts in the concentration-response curves to L-cysteine and attenuated the maximum inhibitory response. Conversely, the inhibitor of cystathionine gamma-lyase, PAG (1 mM) blocked only relaxations caused by high concentrations of L-cysteine (> 100 microM). CONCLUSIONS: The inhibitory action of L-cysteine in isolated porcine irides is dependent on the endogenous production of H(2)S by cystathionine gamma-lyase and cystathionine beta-synthase. Furthermore, prostanoids and K(ATP) channels are involved in the inhibitory action of L-cysteine in this tissue.
PURPOSE: To investigate the direct pharmacological actions of L-cysteine, a substrate for the production of H(2)S, 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 degrees 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 H(2)S, and prostanoids. In addition, we also examined the effect of ATP-sensitive K(+) (K(ATP)) 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, reaching a maximum inhibition of 43% at 1 mM. This response was enhanced significantly (P < 0.001) in the presence of the COX inhibitor, flurbiprofen (3 microM). Additionally,in the presence of flurbiprofen, the H(2)S donors, NaHS and Na(2)S, mimicked the relaxations produced by L-cysteine, yielding IC(50) values of 5.8 microM and 180 microM, respectively. Both the inhibitor of cystathionine beta-synthase, AOA (30 microM) and the K(ATP) channel antagonist, glibenclamide (100 microM) caused significant (P < 0.001) rightward shifts in the concentration-response curves to L-cysteine and attenuated the maximum inhibitory response. Conversely, the inhibitor of cystathionine gamma-lyase, PAG (1 mM) blocked only relaxations caused by high concentrations of L-cysteine (> 100 microM). CONCLUSIONS: The inhibitory action of L-cysteine in isolated porcine irides is dependent on the endogenous production of H(2)S by cystathionine gamma-lyase and cystathionine beta-synthase. Furthermore, prostanoids and K(ATP) channels are involved in the inhibitory action of L-cysteine in this tissue.
Authors: Madhura Kulkarni-Chitnis; Ya Fatou Njie-Mbye; Leah Mitchell; Jenaye Robinson; Matthew Whiteman; Mark E Wood; Catherine A Opere; Sunny E Ohia Journal: Exp Eye Res Date: 2015-04-04 Impact factor: 3.467
Authors: Madhura Kulkarni; Ya Fatou Njie-Mbye; Ikechukwu Okpobiri; Min Zhao; Catherine A Opere; Sunny E Ohia Journal: Neurochem Res Date: 2011-05-01 Impact factor: 3.996
Authors: Ankita Salvi; Pratik Bankhele; Jamal M Jamil; Madhura Kulkarni-Chitnis; Ya Fatou Njie-Mbye; Sunny E Ohia; Catherine A Opere Journal: Neurochem Res Date: 2015-12-23 Impact factor: 3.996