Vasoactivity of endothelin in nasal blood vessels

Endothelin (ET) is a newly described peptide that was isolated from the supernatant of cultured porcine aortic endothelial cells. Among the three isoforms of ET, the originally discovered ET-1 is the only one that exists in vascular endothelium. It is reported to be an extremely potent vasoconstrictor in a variety of blood vessels. Using in vitro bioassay technique, the vasoactivity of ET-1 in both canine and human nasal mucosa was investigated. ET produces a contraction which is slow in onset and sustained in the blood vessels both of the canine and the human nasal mucosa. The threshold of ET-1 in causing contraction was 10(-9) M (dog) and 10(-8) M (human). This response was turned out to be extracellular Ca(2+)-dependent, because either Ca(2+)-free medium or application of nifedipine almost abolished it. A subthreshold concentration of ET-1 enhances exogenously applied noradrenaline (NA)-induced contractions, but not endogenous NA-induced contractions caused by transmural electrical stimulation. As endothelium derived substances, such as ET-1 showed strong vasoactivity, endothelium may play an important role in maintaining vascular tension of the nasal blood vessels along with neural control.