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The present study aims to investigate the regulatory effect of hydrogen sulfide (H2S) on cAMP homeostasis and renin degranulation in As4.1 and rat reninrich kidney cells. It was found in the present study that NaHS at 0.1-10 μM significantly decreased cAMP production in As4.1 cells treated with isoproterenol (a β-adrenoceptor agonist), forskolin (an adenylyl cyclase activator), or 3-isobutyl-1-methylxanthine (IBMX, a phosphodiesterase inhibitor). NaHS at 10 μM suppressed adenylate cyclase activity but stimulated phosphodiesterase activity. We continued to study whether H2S may mediate cAMP-dependent renin degranulaion in As4.1 cells. It was found that NaHS at 0.1-10 μM significantly increased intracellular renin protein level. Moreover, NaHS reversed the declined renin content within As4.1 cells and normalized the upregulated renin activity in the culture medium of As4.1 cells treated with the above three stimuli. RT-PCR showed that cystathionine-γ-lyase is the main enzyme to produce endogenous H2S in As4.1 cells. Overexpression of cystathionine-γ-lyase increased endogenous H2S production and suppressed isoproterenol-induced renin release, suggesting that endogenous H2S may also inhibit renin release from As4.1 cells. We also tested whether H2S has a similar effect in renin-rich kidney cells. It was found that isoproterenol elevated intracellular cAMP level and extracellular renin activity but decreased renin protein level in the renin-rich kidney cells. Pretreatment with NaHS abolished these effects. In conclusion, H2S regulates cAMP homeostasis via inhibition of adenylate cyclase and stimulation of phosphodiesterase. Our findings suggest that H2S plays a critical role in regulation of renin degranulation in As4.1 and rat renin-rich kidney cells. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S), an endogenous gaseous mediator, produces both vasorelaxation and vasoconstriction at different concentrations. We found in the present study that NaHS, an H2S donor, produced stronger vasorelaxant and weaker vasoconstrictive effects in HEPES solution compared with those achieved in Krebs solution. We further screened the buffer components and found that bicarbonate (HCO3-) was the ion to influence the effect of H2S. After examining the vasorelaxant effects of acetylcholine, a vasodilator by releasing nitric oxide, and isoprenaline, a β-adrenoceptor agonist, in HEPES and Krebs buffers, we found the HCO3--dependent effect was specific to H2S. Blockade of anion exchanger-2 activity with 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) or with HCO3--free solution abolished the vasoconstrictive effect of NaHS. Moreover, NaHS decreased nitric oxide level in the rat aorta in HCO3--containing buffer, but this effect was abolished by HCO3--free buffer or DIDS. In summary, we found for the first time that H2S stimulates anion exchanger to transport extracellular HCO3- in exchange for intracellular superoxide anions, which may further inactivate nitric oxide and induces vasoconstriction. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H[sub2]S), a new endogenous mediator, produces both vasorelaxation and vasoconstriction. This study was designed to examine whether cAMP mediates the vasoconstrictive effect of H[sub2]S. We found that NaHS at a concentration range of 10-100 μM (yields ∼3-30 μM H[sub2]S) concentration-dependently reversed the vasodilation caused by isoprenaline and salbutamol, two β-adrenoceptor agonists, and forskolin, a selective adenylyl cyclase activator, in phenylephrine-precontracted rat aortic rings. Pretreatment with NaHS (10-1 00 μM) for 5 mm also significantly attenuated the vasorelaxant effect of salbutamol and forskolin. More importantly, NaHS (5-100 μM) significantly reversed forskolin-induced cAMP accumulation in vascular smooth muscle cells. However, NaHS produced significant, but weaker, vasoconstriction in the presence of N[supG]-nitro-L-arginine methyl ester (100 μM), a nitric oxide synthase inhibitor, or in endothelium-denuded aortic rings. Blockade of ATP-sensitive potassium channels with glibenclamide (10 μM) failed to attenuate the vasoconstriction induced by H[sub2]S. Taken together, we demonstrated for the first time that the vasoconstrictive effect of H[sub2]S involves the adenyly cyclase/cAMP pathway. [ABSTRACT FROM AUTHOR]