Importance of calcium in long-term preservation of the vasculature

Background. The aim was to investigate the effect of calcium in organ preservation solutions with respect to 36-hour preservation of vascular smooth muscle function and endothelium-dependent relaxation. Methods. The infrarenal aortas of 60 Sprague-Dawley rats were studied in organ baths as fresh controls and after 36 hours of cold (4°C) storage in different preservation solutions with and without calcium. The thromboxane A2 analogue U-46619 was used to study contractility. Endothelium-dependent relaxation was tested by the cumulative addition of acetylcholine. Papaverine hydrochloride was used to elicit endothelium-independent relaxation. Results. Krebs solution was the only solution able to fully preserve contractility. Krebs solution without calcium gave poor preservation. After the addition of 1.5 mmol/L of calcium to University of Wisconsin solution and to Perfadex, both these solutions became fully able to preserve contractility. None of the solutions (with or without calcium) were fully able to preserve endothelium-dependent relaxation, although University of Wisconsin solution gave good preservation and Perfadex, fair preservation. Euro-Collins solution and K+ (124 mmol/L)-enriched Krebs solution were not able to preserve smooth muscle function or endothelium-dependent relaxation. Conclusion. Calcium is essential for long-term preservation of vascular smooth muscle function but not for long-term preservation of endothelium-dependent relaxation.