Vasodilator responses to acetylcholine are not mediated by the activation of soluble guanylate cyclase or TRPV4 channels in the rat

Abstract

The effects of 1H-[1,2,4]-oxadizaolo [4,3-]quinoxaline-1-one (ODQ), an inhibitor of the activation of soluble guanylate cyclase (sGC) on responses to NO donors acetylcholine (ACh) and bradykinin (BK) were investigated in the pulmonary and systemic vascular beds of the rat. In these studies the administration of ODQ in a dose of 5 mg/kg iv attenuated vasodilator responses to five different NO donors without inhibiting responses to ACh and BK in the systemic and pulmonary vascular beds of the rat. Vasodilator responses to ACh were not inhibited by L-NAME or the transient receptor vanilloid type 4 (TRPV4) antagonist GSK-2193874, which attenuated vasodilator responses to the TRPV4 agonist GSK-1016790A. ODQ did not inhibit vasodilator responses to agents reported to act in an NO-independent manner or to vasoconstrictor agents, and ODQ did not increase blood methemoglobin levels, suggesting that off target effects were minimal. These results show that ODQ in a dose that inhibited NO donor-mediated responses did not alter vasodilator responses to ACh in the pulmonary and systemic vascular beds and did not alter systemic vasodilator responses to BK. The present results indicate that decreases in pulmonary and systemic arterial pressures in response to ACh are not mediated by the activation of sGC or TRPV4 channels and that ODQ can be used to study the role of the activation of sGC in mediating vasodilator responses in the rat. pulmonary vascular bed; transient receptor vanilloid type; vasodilation CYCLIC GUANOSINE MONOPHOSPHATE (cGMP) has an important role in the regulation of vascular smooth muscle tone and is synthesized from guanosine triphosphate (GTP) by soluble guanylate cyclase (sGC), the receptor for nitric oxide (NO) (2,29,32,41). sGC is a heterodimeric enzyme, and binding of NO to the heme-containing subunit activates sGC (2). In contrast, oxidation of the heme-containing subunit reduces the sensitivity of the enzyme to NO (7,25,45,48,49). Pharmacological agents and genetic alterations that selectively modulate sGC activity are useful in the study of the physiological function of the enzyme in regulating vascular tone and mediating vasodilator responses (19,35,43).Although the role of NO in the regulation of baseline tone is well established, the role of NO in mediating vasodilator responses to acetylcholine (ACh) and bradykinin (BK) is controversial (4,12,34). A large number of studies show that vasorelaxant responses to ACh are mediated by the NO-cGMP pathway; however, other studies indicate that NO is not involved (13,18,20). It has been hypothesized that vessel size, vascular segment studied, method used, and species may account for differences in the role of NO in mediating responses to ACh and BK reported in the literature (17, 34). Studies in isolated first-order gracilis muscle arterioles from endothelial NOS (eNOS) knockout mice show that responses to ACh were only slightly attenuated, and studies in eNOS and cGMPdependent protein kinase type-1 (cGKI) knockout mice show that vasodepressor responses to...

Analysis of cardiovascular responses to the H2S donors Na2S and NaHS in the rat

“…The observation that blood pressure responses to the H 2 S donors in the intact chest rat are not attenuated by glybenclamide or L-NAME does not mean that K ATP channels or NO is not involved in mediating responses in some local vascular segments or regions. The present data indicate that K ATP channels or NO does not play a major role in mediating the overall decreases in systemic arterial pressure in response to intravenous injections of the H 2 S donors in the rat and are similar to data in eNOS knockout mice where the hypotensive response to acetylcholine is not impaired but that vasodilator responses in some regional vascular segments isolated from eNOS knockout mice are attenuated (16,25,33).…”

“…For the measurement of pulmonary arterial pressure, a specially designed 3-F single-lumen catheter with a curved tip and radioopaque marker was passed from the right jugular vein into the main pulmonary artery under fluoroscopic guidance (Picker-Surveyor Fluoroscope) as described previously (19,(33)(34)(35). Pulmonary arterial pressure was measured with a Namic Perceptor DT pressure transducer and data acquisition system and stored on the PC.…”

“…Miconazole (Sigma-Aldrich) was dissolved in DMSO. The doses of the antagonists used in the present study were determined from doses used in previous studies in the literature and from pilot studies in our laboratory (11,29,(33)(34)(35)50). The vehicles for the drugs used in the study did not alter responses to Na 2S and NaHS.…”

Nitric Oxide–Dependent Feedback Loop Regulates Transient Receptor Potential Vanilloid 4 (TRPV4) Channel Cooperativity and Endothelial Function in Small Pulmonary Arteries

“…Both ECs and SMCs from PAs showed a strong expression of PKG (Figure 5B). Similar to L‐NNA, GC inhibitor ODQ (3 μmol/L)44 and PKG inhibitor Rp‐8‐Br‐PET‐CGMPS (PET; 30 μmol/L)45 increased the baseline sparklet activity by ≈2‐fold (Figure 5C), confirming that GC‐PKG signaling constitutively inhibits TRPV4 channels in PA endothelium. In the presence of GC or PKG inhibitor, L‐NNA was unable to further increase the activity of TRPV4 sparklets (Figure 5C, left ).…”

Muscarinic Receptor Activation Affects Pulmonary Artery Contractility in Sheep: The Impact of Maturation and Chronic Hypoxia on Endothelium-Dependent and Endothelium-Independent Function

“…mAChR activation of the endothelium reduces pulmonary arterial tension or vascular pressures in multiple animals, including mice, rats, and sheep in addition to humans (Storme et al, 1999;Peyter et al, 2008;Rowell et al, 2009;Pankey et al, 2014). Endothelial cell mAChR stimulation induces intracellular Ca 2+ responses that activate multiple signaling pathways, including endothelial nitric oxide synthase (eNOS), phospholipase A 2 (PLA 2 ), and myoendothelial junctions (Norel et al, 1996;Walch et al, 2001;Papamatheakis et al, 2013).…”