Endogenous production of hydrogen sulfide in isolated bovine eye

Hydrogen sulfide (H ₂S) is a novel gasotransmitter with physiological and pathological functions in vascular homeostasis, cardiovascular system and central nervous system. In the present study, we determined the endogenous levels of H ₂S in various tissues of the bovine eye. We also examined the basal levels of H ₂S in response to donors (sodium hydrosulfide, NaHS and sodium sulfide, Na ₂S), substrate (l-cysteine), inhibitors (propargylglycine, PAG and aminooxyacetic acid, AOA) and activator (S-adenosyl-l-methionine, SAM) of this gas in the bovine retina. H ₂S was measured using a well established spectrophotometric method. The highest concentration of endogenous H ₂S was detected in cornea (19 ± 2.85 nmoles/mg protein, n = 6) and retina (17 ± 2.1 nmoles/mg protein, n = 6). Interestingly, H ₂S was not present in vitreous humor. The inhibitors of CSE and CBS; PAG (1 mM) and AOA (1 mM), significantly attenuated the production of H ₂S in the bovine retina by 56.8 and 42%, respectively. On the other hand the activator of CBS; SAM (100 μM), H ₂S donors; NaHS (1 μM) and Na ₂S (100 μM), significantly increased endogenous levels of H ₂S in bovine retina. l-cysteine (10-300 μM) produced a significant (P <0.05) concentration-dependent increase in H ₂S levels reaching a maximal at 300 μM. We conclude that H ₂S is endogenously produced in various tissues of the isolated bovine eye. Moreover, endogenous levels of H ₂S are enhanced in the presence of substrate (l-cysteine), an activator of CBS (SAM) and H ₂S donors but are blocked by inhibitors of enzymes that synthesize this gas in neural retina.