BP and Vascular Function Following Space Flight

Blood pressure and mesenteric resistance artery function were assessed in 9-week-old spontaneously hypertensive rats following an 18 day shuttle flight on STS-80. Blood pressure was measured twice, first in conscious animals using a tail-cuff method and then while the animals were anesthetized with 2% halothane in O2. Isolated mesenteric resistance artery responses to cumulative additions of norepinephrine, acetylcholine, sodium nitroprusside, and calcium were measured within 17 hours of landing using wire myography. Blood pressure was slightly reduced in conscious animals following flight (p=0.056) but was significantly elevated (p less than.001) above vivarium control group values in anesthetized animals. Maximal contraction of mesenteric arteries to norepinephrine was attenuated in the flight animals (p less than.001)aswasrelaxationtoacetylcholine(p less than .001)andcalcium(p less than .05). There was no difference between flight and control animals in the vessel response to sodium nitroprusside (p greater than .05). The results suggest that there may have been an increase in synthesis and release of nitric oxide in the flight animals.