Retention of endothelium-dependent properties in human mammary arteries after cryopreservation

Background. We investigated the effects of cryopreservation and antibiotic treatment on endothelium-dependent vasomotor properties of human internal mammary arteries (IMAs). Methods. Sixty IMA specimens from routine coronary artery bypass grafting procedures were randomly assigned to six groups. Group I (controls) were immediately tested after harvest. Remaining groups were prepared according to a stepwise design: group II, 6 hours of warm ischemia; group III, 6 hours of warm ischemia + 24 hours at 4°C (without antibiotics); group IV, 6 hours of warm ischemia + 24 hours of 4°C antibiotic disinfection; group V, 6 hours of warm ischemia + 24 hours at 4°C (without antibiotics) + cryopreservation; and group VI, 6 hours of warm ischemia + 24 hours of 4°C disinfection + cryopreservation. The IMA specimens were cut into rings and the tension of vascular smooth muscle was recorded. The IMA rings were contracted with norepinephrine (3 x 10^-6 mol/L) and tested with cumulative concentrations of acetylcholine (from 1 x 10^-9 to 1 x 10^-5 mol/L), contracted with endothelin-1 (from 1x 10^-11 to 1 x 10^-6 mol/L), and contracted with the nitric oxide-synthase inhibitor N(G)-monomethyl-L-arginine (1 x 10^-4 mol/L). Rings were also tested tor their capacity to generate 6-keto-prostaglandin F₁ (the stable metabolite of prostacyclin), and endothelial cell viability rate was finally evaluated with the trypan blue dye exclusion method. Results. Our results show that a complete cryopreservation protocol does not significantly modify (p > 0.05) the relaxant activity to acetylcholine in norepinephrine-precontracted IMA rings (controls; 90.2% ± 4.2% vs group VI, 77.1% ± 6.2%) or the vasoconstrictor response induced by endothelin-1 (controls, 62.6% ± 2.8% versus group VI, 73.7% ± 4.8%) and N(G)-monomethyl-L-arginine (controls, 22.4% ± 1.5% versus group VI, 18.9% ± 1.9%). Furthermore, IMA cryopreservation does not significantly modify (p > 0.05) the endothelial release of prostacyclin either in basal conditions (-20% versus controls) or during pharmacologic intervention with acetylcholine (-18% versus controls), endothelin-1 (-17% versus controls), and N(G)-monomethyl-L-arginine (-18% versus controls). Conclusions. We conclude that the IMA endothelial function does not seem significantly injured by any of the current steps of disinfection and cryopreservation.