Abstract
Introduction: :
Evidence from our laboratory shows that the hydrogen sulfide (H2S) donor, sodium hydrosulfide (NaHS) can inhibit electrically–evoked [3H]–norepinephrine ([3H]NE) release from isolated porcine iris–ciliary bodies (Ohia et al; IOVS 46: E–Abstract 2383, 2005). It is, however, unclear whether the inhibitory effects caused by this gas on NE release could be due to a direct action on neurotransmitter pools in sympathetic nerves.
Purpose: :
(1) To investigate the effect of H2S (using sodium hydrosulfide, NaHS as H2S donor) on NE, dopamine (DA) and epinephrine (EP) concentrations in porcine iris–ciliary body and neural retina and (2) to compare effect of NaHS on ocular tissues with those from the rat brain cortex.
Methods: :
Isolated porcine iris–ciliary bodies, neural retina and rat brain cortex slices were incubated in warm oxygenated Krebs solution containing different concentrations of NaHS (10 – 300 µM) for 15 minutes. After incubation, catecholamines in tissue homogenates and media were extracted with 0.2 N perchloric acid and assayed by HPLC–ED.
Results: :
In porcine iris–ciliary bodies, concentrations of NaHS greater than 100 µM significantly (P < 0.001) reduced both NE and DA levels when compared to controls. For instance, NaHS (300 µM) decreased NE and DA levels by 40 % and 33 %, respectively. In contrast, NaHS had no significant (P > 0.05) effect on EP levels in the ICB. In the porcine retina, NaHS (10 – 300 µM) caused a concentration–dependent decrease in NE levels reaching a maximum of 40% at 100 µM. In the rat brain cortex, NaHS (10 – 300 µM) also significantly (P < 0.001) reduced the levels of both NE and DA reaching a maximum of 25 % and 60%, respectively, at 100 µM.
Conclusions: :
We conclude that H2S can alter catecholamine levels in both mammalian ocular and brain tissues, in vitro. The observed inhibitory action of this gas on neurotransmitter pools merits further investigation.
Keywords: neurotransmitters/neurotransmitter systems • uvea • retina