EFFECTS OF CRYOPRESERVATION ON CONTRACTILE PROPERTIES OF PORCINE ISOLATED AORTIC-VALVE LEAFLETS AND AORTIC-WALL

Human semilunar donor heart valves can be stored in banks, awaiting tr ansplantation. To evaluate the result of the preservation protocols, a quantitative description of the tissue is necessary. In this study we investigated in a quantitative way the contractile properties of fres h and cryopreserved porcine isolated aortic heart valve leaflets in re sponse to a number of endogenous vasoactive compounds, The responses o f strips of the aortic wall were included for comparison. Contraction was measured isometrically in response to potassium (K+; 100 mmol/L), 5-hydroxytryptamine (1 nmol/L to 100 mu mol/L), noradrenaline (1 nmol/ L to 100 mu mol/L), endothelin-1 (0.01 nmol/L to 0.3 mu mol/L), and pr ostaglandin F-2 alpha (0.1 nmol/L to 10 mu mol/L). The pharmacologic p arameters E(MAX) (the maximal response expressed as a percentage of co ntraction to a 100 mmol/L dose of K+) and EC(50) (the concentration th at produces 50% of the maximal effect) were calculated for every compo und (n = 6 to 7 each), We observed that all specimens contracted in re sponse to potassium, Its magnitude in fresh leaflets equaled 1.6 +/- 0 .14 mN compared with 26.6 +/- 2.6 mN in fresh aortic wall, Noradrenali ne, endothelin-1, and prostaglandin F-2 alpha all caused contraction i n valvular leaflets and aortic wall, whereas 5-hydroxytryptamine cause d contraction in the valvular leaflets but relaxation in aortic wall, After cryopreservation, the response to K+ amounted to 24% of the resp onse of the fresh specimens in valvular leaflets (n = 25) and 14% in a ortic wall (n = 26), The values of E(MAX) and EC(50) of the responses to noradrenaline, endothelin-1, and prostaglandin F-2 alpha remained u nchanged. Although the physiologic relevance of contraction of valvula r leaflets needs further study, its measurement may provide an additio nal model to verify the consequences of alternative methods of preserv ation.