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 degrees 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 3H]-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 micromol/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.