Different patterns of H2S/NO activity and cross-talk in the control of the coronary vascular bed under normotensive or hypertensive conditions.

Hydrogen sulfide (H2S) and nitric oxide (NO) play pivotal roles in the cardiovascular system. Conflicting results have been reported about their cross-talk. This study investigated their interplays in coronary bed of normotensive (NTRs) and spontaneously hypertensive rats (SHRs). The effects of H2S- (NaHS) and NO-donors (sodium nitroprusside, SNP) on coronary flow (CF) were measured in Langendorff-perfused hearts of NTRs and SHRs, in the absence or in the presence of propargylglycine (PAG, inhibitor of H2S biosynthesis), L-NAME (inhibitor of NO biosynthesis), ODQ (inhibitor of guanylate cyclase), L-Cysteine (substrate for H2S biosynthesis) or L-Arginine (substrate for NO biosynthesis). In NTRs, NaHS and SNP increased CF; their effects were particularly evident in Angiotensin II (AngII)-contracted coronary arteries. The dilatory effects of NaHS were abolished by L-NAME and ODQ; conversely, PAG abolished the effects of SNP. In SHRs, high levels of myocardial ROS production were observed. NaHS and SNP did not reduce the oxidative stress, but produced clear increases of the basal CF. In contrast, in AngII-contracted coronary arteries of SHRs, significant hyporeactivity to NaHS and SNP was observed. In SHRs, the vasodilatory effects of NaHS were only modestly affected by L-NAME and ODQ; PAG poorly influenced the effects of SNP. Then, in NTRs, the vascular actions of H2S required NO and vice versa. By contrast, in SHRs, the H2S-induced actions scarcely depend on NO release; as well, the NO effects are largely H2S-independent. These results represent the first step for understanding pathophysiological mechanisms of NO/H2S interplays under both normotensive and hypertensive conditions.