吸入异氟烷对大鼠肺表面活性蛋白A(SP-A)基因表达的影响

Effects of isoflurane on lung surfactant protein-A (SP-A) in rats

目的观察大鼠吸入1.5%异氟烷不同时间后肺表面活性蛋白-A(SP-A)的含量及其基因表达的改变情况。方法雄性Wister大鼠40只,随机分为5组,每组8只。正常对照组(Con),异氟烷2h组、4h组和8h组分别为吸入40%O2+1.5%异氟醚2、4和8h组;停药2h组(10h组)吸入40%O2+1.5%异氟醚8h后再吸入40%O22h。各组于实验结束后取出大鼠迅速处死,检测支气管肺泡灌洗液(BALF)中表面活性蛋白A(SP-A)的含量(WesternBlot法);肺组织内SP-A含量(WesternBlot法)以及SP-AmRNA的表达(RT-PCR法)。结果吸入异氟烷2h组BALF中SP-A的含量与对照组比较无明显变化,4h、8h组均较对照组显著下降(P<0.01),10h组未见明显恢复(P<0.01)。肺组织内SP-A的含量在2h组无明显改变,但4h、8h组明显下降(P<0.01),10h组有所恢复,但仍低于对照组(P<0.05)。吸入异氟烷的各组SP-AmRNA的表达均有降低趋势(P<0.05),停药2h后(10h)明显恢复。结论吸入1.5%异氟烷2h以上可降低肺组织SP-A的基因表达,继而SP-A的合成与分泌减少;但停止吸入2h后,SP-A基因表达可恢复至正常水平,而其合成与分泌功能仍未能完全恢复。

Objective This study was carried out to evaluate the expression of SP-AmRNA in the lung of rats exposed to 1.5% isoflurane for different time periods. Methods Forty male Wistar rats were randomly divided into 5 groups： normal control group（n=8）, unexposed to isoflurane; group and 2h group （n=8）, for 4h group （n=8） and for 8h group （n=8）. In the laters groups, rats were exposed to 1.5% isoflurane with 40%02 for 2, 4 and 8 hours respectively; while the 10hr group （n=8） were exposed to 1.5% isoflurane for 8 hours, then inhaled 40%O2 for 2 hours. The rats were sacrificed at the end of the appointed inhalation immediately. Surfactant protein A （SP-A） contents in broncho-alveolar lavage fluid （BALF） and the lung tissue were measured with Western Bloting （WB）. To assess the relative levels of SP-AmRNA in lung tissue, reverse transcriptasc-polymerase chain reaction （RT-PCR） was used with the co-amplification of the ＂housekeeping＂ gene GAPDH as internal control. Results Compared to those in the normal control group, SP-A contents in BALF of the 4h and 8h groups were found to decrease significantly, and this was not recovered in 10hr group. SP-A contents of lung tissue were significantly reduced in 4h group and 8hr group. In lOh group, the SP-A content was partly recovered, but still lower than control group. In 2h group, the levels of SP-A in BALF and the lung tissue did not show any significant difference from control. Expression of SP-AmRNA result showed different pattern from those of SP-A contents of BALF and lung tissue. Using RT-PCR we found significantly reduced expressians of SP-AmRNA in the lung tissue in 2h, 4h and 8h groups. However, SP-AmRNA level in the lung tissue was restored to control levels in 10h group. Conclusions These findings indicate that isoflurane exposure for 2 hours or more can decrease the expression of the SP-AmRNA in rats, then decrease the synthesis and secretion of SP-A; whereas the effect of SP-AmRNA can be recovered within 2 hours after isoflurane withdrawal, but the restore of synthesis and secretion is delayed.