N-substituted analogues of S-nitroso-N-acetyl-DL-penicillamine: chemical stability and prolonged nitric oxide mediated vasodilatation in isolated rat femoral arteries

摘要

class="enumerated" style="list-style-type:decimal">Previous studies show that linking acetylated glucosamine to S-nitroso-N-acetyl-D,L-penicillamine (SNAP) stabilizes the molecule and causes it to elicit unusually prolonged vasodilator effects in endothelium-denuded, isolated rat femoral arteries. Here we studied the propanoyl (SNPP; 3 carbon side-chain), valeryl (SNVP; 5C) and heptanoyl (SNHP; 7C) N-substituted analogues of SNAP (2C), to further investigate other molecular characteristics that might influence chemical stability and duration of vascular action of S-nitrosothiols.Spectrophotometric analysis revealed that SNVP was the most stable analogue in solution. Decomposition of all four compounds was accelerated by Cu(II) and cysteine, and neocuproine, a specific Cu(I) chelator, slowed decomposition of SNHP. Generation of NO from the compounds was confirmed by electrochemical detection at 37°C.Bolus injections of SNAP (10 μl; 10⁻⁸–10⁻³ M) into the perfusate of precontracted, isolated rat femoral arteries taken from adult male Wistar rats (400–500 g), caused concentration-dependent, transient vasodilatations irrespective of endothelial integrity. Equivalent vasodilatations induced by SNVP and SNHP were transient in endothelium-intact vessels but failed to recover to pre-injection pressures at moderate and high concentrations (10⁻⁶–10⁻³ M) in those denuded of endothelium. This sustained effect (>1 h) was most prevalent with SNHP and was largely reversed by the NO scavenger, haemoglobin.We suggest that increased lipophilicity of SNAP analogues with longer sidechains facilitates their retention by endothelium-denuded vessels; subsequent slow decomposition within the tissue generates sufficient NO to cause prolonged vasodilatation. This is a potentially useful characteristic for targeting NO delivery to areas of endothelial damage.