ABSTRACT
<p><b>AIM</b>To study the effects of different acute hypoxia on blood pressure, heart rate and microvessels and free radical in rabbits.</p><p><b>METHODS</b>The experiment model was carried out with acute hypoxia on two groups of rabbits, using artificial inspiration 12.5% O2 and 87.5% N2, 8.5% O2 and 91.5% N2 (equivalent to altitudes of some 4 000 m and 6 500 m) keeping hypoxia for 5, 10, 15, 20 min. During the course of it, the changes of blood pressure, heart rate and microvessels response, superoxide dismutase (SOD), malondialdehyde (MDA) were recorded accordingly.</p><p><b>RESULTS</b>(1) systolic pressure was slightly up, then down in 5 mins. Diastolic pressure was significantly down (P < 0.05) in 20 min. (2) Heart rate showed reduced and prolonged, particularly in 8.5% hypoxia group (P < 0.05). (3) Vas bores of microvessle expanded (P < 0.05) and the blood stream became slow gradually (P < 0.05, P < 0.01) in following acute hypoxia time. (4) SOD was significantly down (P < 0.05), MDA was significantly increased (P < 0.05) in 20 mins.</p><p><b>CONCLUSION</b>Acute hypoxia could cause the blood pressure and heart rate to decrease, vas bore of microvessle to expand, the blood circulation to slow down and free radicals would increase.</p>