Temperature-dependent basal tone in isolated human saphenous veins: implication of TP-receptors

Cutaneous blood Vessels are very sensitive to changes in environmental temp erature. The influence of variations in local temperature on the mechanisms involved in the basal tone, present in isolated human saphenous veins has not yet been studied. In the present study, segments with and without endot helium of human saphenous veins obtained from coronary bypass surgery patie nts were mounted for isometric tension recording in oxygenated physiologica l salt solution (PSS). After stabilisation of the basal tone, the local tem perature was rapidly either decreased from 37 degreesC to 24 degreesC (cool ing) or increased from 37 degreesC to 42 degreesC (warming). When antagonis ts or inhibitors were used the preparations were incubated for 30 min with the drugs. During basal conditions, cooling caused relaxations of the saphe nous vein segments with endothelium and warming caused contractions; the ab sence of the endothelium did not modify these responses. In veins without e ndothelium, the warming-induced contractions were significantly inhibited b y verapamil (10 muM) and by the antagonist of TP-receptors (receptors for t hromboxane A(2)) Bay u 3405 (1 muM). The warming induced contractions were not affected by cyclooxygenase or lipoxygenase inhibition. At 37 degreesC, the isoprostanes (8-iso-PGE(2) and 8-iso-PGF(2 alpha)) induced potent contr actions that were significantly inhibited by Bay u 3405 (1 muM). The data s how that a basal tone is present in isolated resting human saphenous vein s egments at 37 degreesC. This basal tone is decreased by local cooling and e nhanced by local warming and is not dependent on the presence of the endoth elium. The warming-induced contraction of the veins is mediated by a non-cy clooxygenase, non-lipoxygenase metabolite (isoprostane?) that interacts wit h TP-receptors and via an extracellular calcium-dependent pathway. (C) 2000 Editions scientifiques et medicales Elsevier SAS.