Difference in the effects of low temperatures on the tension of human pulmonary artery and vein ring segments.
Although limited data suggest that pulmonary flushing with organ preservation solutions should not be performed at too low temperatures, the influence of temperature on pulmonary vascular tone is unclear. The purpose of this study was to examine the effect of low temperatures of the tension of human pulmonary artery and vein ring segments and the vascular resistance of perfused rat lungs. 5 sets of human pulmonary artery and vein ring segments were suspended from a force displacement transducer at 37, 24 and 8 degrees C, and the effect of 30 mM K(+) on the tension was monitored. The effect of 30 mM K(+) on vascular resistance was also examined at low temperatures in 5 perfused rat lungs. Pulmonary artery segments dilated at 24 degrees C, and more significant vasodilatation was observed at 8 degrees C. In contrast, there was a significant constriction of pulmonary veins at 8 degrees C. Vasoconstriction induced by 30 mM K(+) at 37 degrees C was significantly inhibited at low temperatures in both pulmonary arteries and veins. In rat lungs, perfusion at 8 degrees C caused a significant increase in pulmonary vascular resistance, even though no further increase was observed in the presence of 30 mM K(+). Our data indicate that pulmonary arteries dilate and the veins constrict at 8 degrees C and may increase pulmonary vascular resistance. We conclude that the different effect of low temperatures between pulmonary arteries and veins may explain why pulmonary vascular flushing with organ preservation solutions at room temperature is more satisfactory.