The preparation of animal model with prenatal hypoxic adaptation / 中华麻醉学杂志

ABSTRACT

ve To determine the most approprite hypoxic concentration and duration for prenatal hypoxic adaptation animal experiment by exposing pregnant rats to the hypoxic air of different oxygen concentration.Methods Full-term pregnant rats( gestation time 22 days) were placed in an airtight cabin specially designed for hypoxic adaptation experiment. The rats were divided into 7 groups. The Q2 concentration in the airtight cabin was decreased from 21% (group Ⅰ as control) to 18% (group Ⅱ), 17% (group Ⅲ), 16% (group Ⅳ), 15% (group Ⅴ), 14% (group Ⅵ) and 13% (group Ⅶ) respectively. The animals were exposed to short duration of hypoxic air twice with a break of 5min breathing fresh air. The duration of the first hypoxic episode lasted 10 min (group Ⅰ ) , 5 min (group Ⅱ), 7.5min (group Ⅲ), 9.83 min (group Ⅳ), 11.5 min (group Ⅴ), 13.17 min (group Ⅵ) and 14 min (group Ⅶ) respectively. The second hypoxic episode lasted 10min, 9.33 min, 11 min, 15.17 min, 13.33 min, 17 min and 18 min respectively. Ten newborn rats (1 day after birth) randomly selected from each group were placed in a 100ml airtight bottle and the duration from the start to the time when the newborn rat stopped breathing was recorded as hypoxia surviving time. Another 10 newborn rats randomly selected from each group were decapitated and brain was removed for light and electron microscopic examination to determine the degree of neuronal damages. Results In group Ⅰ-Ⅴ the newborn rats were normal (pink skin color and good extremity movement) . In group VI 10/55 (18%) newborn rats were cyanotic with diminished extremity movement, the others were normal. In group VIII 11/52(21% ) newborn rats died, 14/ 52(27%) were cyanotic with diminished extremity movement. Neuronal damages could be seen in cyanoticnewborn rats including decreased number, swelling, apoptosis of neurons and expanded mitochondria. The hypoxia surviving time was significantly longer in group Ⅳ, Ⅴ and Ⅵ than that in control group. Conclusions Hypoxic air containing 15% O2 is appropriate for animal experiment of prenatal hypoxic adaptation. It is better to divide prenatal hypoxia into two episodes lasting 11.5 min and 13.33 min with a break of 5 min between them when animals breathe fresh air.