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 Ill, 6 hours of warm ischemia + 24 hours at 4 degrees C (without antibiotics); group IV, 6 hours of warm ischemia + 24 hours of 4 degrees C antibiotic disinfection; group V, 6 hours of warm ischemia + 24 hours at 4 degrees C (without antibiotics) + cryopreservation; and group VI, 6 hours of warm ischemia + 24 hours of 4 degrees 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 1 x 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 for their capacity to generate 6-keto-prostaglandin F-1 (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.