The contribution of guanylyl cyclase and potassium channels to the relaxation induced by the NO donors [Ru(terpy)(bdq)NO+]3+ (Terpy) and sodium nitroprusside (SNP) in rat mesenteric resistance arteries

Abstract

This study aimed to verify the mechanisms of vasodilatation induced by Terpy and SNP in resistance mesenteric arteries isolated from normotensive (2K) and renal hypertensive rats (2K‐1C). We also studied the inhibitory effects of the guanylyl‐cyclase (GC) with ODQ and K+ channel with TEA. Cumulative concentration‐effect curves to Terpy (0.01 μM‐ 0.01mM) and sodium nitroprusside (SNP 1nM‐0.1mM) were constructed in the third branch of mesenteric arteries pre‐contracted with phenylephrine. We have analyzed the efficacy (ME) and the potency (pD2) of the NO donors. Both SNP and Terpy induced relaxation with similar efficacy in 2K (Terpy 93.8±1.2%, n=7 SNP 96.1±0.7% n=6) and 2K‐1C rats (Terpy 93.7±1.4% n=8, SNP 90.2±4.2% n=5). However, Terpy was less potent (pD2) (2K 4.45±0.3; 2K‐1C 4.51±0.3) than SNP (2K: 6.60±0.2, 2K‐1C: 7.28±0.01), although the relaxation induced by Terpy and SNP, were not different in mesenteric resistance arteries from 2K and 2K‐1C. The incubation with ODQ (1μM) almost abolished the response induced by Terpy and SNP. TEA (1mM) reduced the effect of Terpy in a similar way in 2K (ME: Terpy 73.1±7.3% n=5; SNP 69.2±6.2% n=7) and 2K‐1C rats (Terpy 71.7±8.2% n=5; SNP 77.1±6.6% n=7). In conclusion, in mesenteric resistance arteries from hypertensive and normotensive rats the NO donors Terpy and SNP induce relaxation in a similar way, which involves GC and K+ channels activation. Supported by FAPESP and CNPq.