Low temperature augments the endothelium-dependent relaxation in isolated rat aorta

The norepinephrine-induced contraction in isolated rat aorta was relaxed (by approximately 35%) by a decrease in bath temperature from 37 to 35 degrees C and was augmented (by approximately 30%) by an increase to 39 degrees C. The effect of temperature was inhibited by endothelium removal, methylene blue or hemoglobin. The carbachol-induced, endothelium-dependent relaxation and the sodium nitroprusside-induced relaxation were decreased at 39 degrees C and increased at 35 degrees C. These results suggest that low temperature augments the effect of inhibitory substances released from vascular endothelium, possibly by a change in the sensitivity of smooth muscle cells to this substance.