ENDOTHELIAL-DEPENDENT DYNAMIC AND ANTITHROMBOTIC PROPERTIES OF PORCINE AORTIC AND PULMONARY VALVES

Background. In the present study, the endothelium-dependent antithromb otic and dynamic properties of porcine aortic (AoV) and pulmonary valv es (PuV) were investigated. Methods. Fifteen fresh AoV and 15 fresh Pu V were obtained from 25 9-month-old swines. The valves were examined f or endothelial function by pharmacologic evaluation (with and without endothelium) of both the endothelial-releasing capacity of prostacycli n and the endothelial-dependent dynamic response to relaxing (acetylch oline from 10(-10) mol/L to 10(-4) mol/L in AoV and PuV segments preco ntracted with norepinephrine [3 x 10(-6) mol/L]) and contracting (endo thelin-l, from 10(-11) mol/L to 10(-5) mol/L; and N-G-monomethyl-L-arg inine, 10(-4) mol/L) drugs. The ultrastructural integrity of the endot helial valve layer was also examined with transmission electron micros copy. Results. Acetylcholine caused potent relaxation in both AoV and PuV specimens with, but not in those without, endothelium. Endothelin- 1 produced a concentration-dependent tension increase in AoV and PuV w ith and without endothelium. However, the intrinsic activity of the pe ptide significantly increased in tissues without endothelium. N-G-mono methyl-L-arginine evoked a progressive increase in resting tension of the preparations, but the AoV and PuV without endothelium were less se nsitive to the inhibition of the nitric oxide generation. Aortic and p ulmonary valves with an intact endothelium showed a spontaneous abilit y to release prostacyclin. The basal release of this lipidic autacoid significantly decreased in cardiac valves without endothelium. This ph enomenon was observed in both basal conditions, and under stimulation with the aforementioned drugs. Transmission electron microscopy showed the perfect preservation of endothelial cells in all the preparations examined. Conclusions. Valvular endothelium of AoV and PuV seems to h ave similar antithrombotic and dynamic functions of vascular endotheli um, actively participating in valvular homeostasis. (C) 1998 by The So ciety of Thoracic Surgeons.