Impaired EDHF-Mediated Relaxation in Porcine Pulmonary Micro-Arteries by Cold Storage with University of Wisconsin and Euro-Collins Solutions

Background: Vascular endothelium plays a key role in regulation of vascular tone. Hyperkalemia has been demonstrated to impair the EDHF‐mediated endothelial function in coronary circulation. University of Wisconsin (UW) and Eruo‐collins (EC) solutions are used for organ preservation in transplantation surgery. The potassium concentration in UW or EC solutions is as high as 125 mmol/L or 115 mmol/L, respectively. This study was designed to examine whether hyperkalemia or storage with UW and EC solutions affects the relaxation mediated by EDHF in the porcine pulmonary micro‐arteries. Methods: Porcine pulmonary micro‐artery rings (diameter 200–450 μm) were studied in myograph (n = 8 in each group). After incubation with hyperkalemia (K⁺ 125 mmol/L, at 37° C), UW or EC solutions (at 4° C for 4 hours), EDHF‐mediated relaxation induced by bradykinin (BK, ?10 to ?6.5 log M) in the presence of inhibitors for cyclooxygenase (Indomethacin, 7 μM), nitric oxide synthase (N^G‐nitro‐_L‐arginine, 300 μM), and oxyhemoglobin (20 μM) was compared with control (Krebs' solution) in precontraction with U₄₆₆₁₉ (?7.5 log M). Results: The EDHF‐mediated relaxation to BK was 69.6 ± 6.3% compared with 97.1 ± 1.7% (p= 0.003) in control (no inhibitors). After incubation with hyperkalemia, the relaxation significantly decreased (38.6 ± 3.0% vs. 59.1 ± 7.4%, p= 0.03 ). Storage with UW or EC solutions also significantly decreased the relaxation (49.3 ± 7.3% vs. 65.2 ± 3.5%, p= 0.04 and 51.9 ± 8.4% vs. 60.3 ± 6.1%, p= 0.02 , respectively). Conclusions: In porcine pulmonary micro‐arteries, exposure to hyperkalemia or storage with UW or EC solutions at 4°C for 4 hours impairs the EDHF‐mediated endothelial function. The clinical significance of this effect should be further studied.