Involvement of Prostaglandins in the Pharmacological Actions of L‐Cysteine in Ocular Tissues

Abstract

Evidence from our laboratory demonstrates that hydrogen sulfide (H2S) can exert pharmacological actions in ocular tissues, an effect that can be blocked by inhibitors of cyclooxygenase (COX).PurposeTo investigate whether H2S (using L‐cysteine as substrate) can alter prostaglandin E2 (PGE2) production in isolated bovine irides and retina.MethodsIsolated bovine irides and retinae were incubated in oxygenated Krebs buffer for 30 mins, prior to treatment with different concentrations of L‐cysteine (1 nM ‐ 10 µM) and norepinephrine (NE, 1 µM). After incubation and termination of reaction, tissues were homogenized and both homogenates and incubation media were collected and prepared for PGE2 Enzyme‐immunoassay (EIA) using a well‐established methodology.ResultsIn both bovine isolated irides and retinae, L‐cysteine elicited a concentration‐dependent (1 nM ‐ 10 µM) increase in PGE2 concentrations over basal levels. For instance, L‐cysteine (10nM; irides) and (10 µM; retina) produced an equi‐effective significant (p< 0.05) increase in PGE2 concentrations over basal levels. In bovine irides (but not retinae), L‐cysteine (10 µM) produced an increase in PGE2 levelsin the incubation media indicating a washout of prostanoids from tissues exposed to L‐cysteine. The positive control, NE (1µM) also caused an increase in PGE2 concentrations over basal levels in ocular tissues.ConclusionL‐cysteine can increase prostaglandin production in isolated bovine irides and retinae, affirming a role for these autacoids in the pharmacology of H2S in the eye.