Vascular effects of hyperthermia on isolated blood vessels

1. The contractile response of isolated human umbilical and sheep renal arteries to 5-hydroxytryptamine (5-HT) with increasing temperatures was investigated. 2. In the umbilical artery the threshold value was lowest at 30 degrees C and increased with increasing temperature, the maximal response being lower at temperatures above 30 degrees C. 3. Spontaneous rhythmic contractions of the umbilical artery were not augmented by warming above 37 degrees C. 4. The sheep renal artery exhibited an opposite response pattern: increasing temperature lowered the threshold and increased the maximal response. 5. Addition of indomethacin to the bathing fluid resulted in increased responsiveness of the umbilical arteries to 5-HT. With lower threshold, ED50 and higher maximal response.