University of Wisconsin solution increases hyperpolarizing mechanisms in response to bradykinin

Background The aim of this study was to determine the effect of University of Wisconsin solution (UWS) incubation on bradykinin-induced vasodilation. Methods Porcine coronary arteries were incubated in Krebs-Henseleit solution (KHS) or UWS at 4°C for 20 hours. Endothelium-dependent relaxation to bradykinin and endothelium-independent relaxation to nitric oxide were tested after U46619 or KCl pre-contraction. Nitric oxide synthase activity and protein expression was determined by [ 3 H]-l-citrulline formation and western blot analysis, respectively. Results The relaxation to bradykinin (0.1 to 300 nmol/liter) after U46619 (30 to 300 nmol/liter) pre-contraction was similar with both KHS and UWS pre-incubation; however, it was reduced after KCl pre-contraction (15 to 20 mmol/liter), this reduction being greater after UWS incubation. The inhibitory effect of N G -nitro-l-arginine methylester (0.1 mmol/liter) on bradykinin-induced relaxation was lower in UWS- than KHS-incubated segments after U46619 pre-contraction, but similar after KCl pre-contraction; however, the inhibitory effect of 0.5 mmol/liter ouabain was unaffected. Tetraethylammonium (5 mmol/liter) reduced the response to bradykinin more strongly after UWS pre-incubation. UWS did not modify relaxation to nitric oxide (0.1 to 30 μmol/liter) in pre-incubated UWS or KHS segments. UWS failed to modify both total nitric oxide synthase activity and endothelial nitric oxide synthase expression. Conclusions UWS incubation decreased nitric oxide participation and increased the hyperpolarizing mechanisms produced by bradykinin.