Lines A, Gillett A M, Phillips I D, Wallace M J, Hooper S B
Department of Physiology, Monash University, Clayton, Victoria, 3168, Australia.
Exp Physiol. 2001 Jan;86(1):55-63. doi: 10.1113/eph8602088.
Increased fetal lung expansion, induced by tracheal obstruction (TO), is a potent stimulus for fetal lung growth, but rapidly reduces surfactant protein (SP) mRNA levels. Our aim was to determine the time course for the re-expression of the surfactant proteins in fetal lung tissue following the release of a TO and to relate these to the changes in lung liquid volume. Fetal sheep were exposed to either: (1) no treatment (controls); (2) 4 days of TO; (3) 4 days of TO, followed by release of the obstruction for 24 h; (4) 4 days of TO followed by release of the obstruction for 3 days. Four days of TO increased lung liquid volumes from 26.8 +/- 1.9 to 72.0 +/- 5.6 ml kg(-1) and reduced SP-A, SP-B and SP-C mRNA levels to 38.5 +/- 10.7, 56.8 +/- 10.3 and 18.3 +/- 5.3 % of control values, respectively. One day after TO release, lung liquid volumes were reduced to 17.4 +/- 5.3 ml kg(-1) (control 128 days, 31.0 +/- 3.8 ml kg(-1)) and SP-A and SP-B mRNA levels were not different from control levels. In contrast, SP-C mRNA levels only increased to 45.4 +/- 17.3 % of control. Three days after TO release, lung liquid volumes increased to 48.0 +/- 8.5 ml kg(-1) and SP-A and SP-B mRNA levels were reduced to 48.8 +/- 10.2 % and 71.5 +/- 19.8 % of control, respectively; SP-C mRNA levels remained at 35.3 +/- 12.3 % of control. Following the release of a TO, SP-A, SP-B and SP-C mRNA levels were closely and inversely related to the volume of lung liquid. Based on these relationships, the lung liquid volumes that equate to 100 % expression were considerably less than control lung volumes (< 10 vs. 30-40 ml kg(-1)) in fetuses of this age. Thus, the changes in fetal lung SP-A, SP-B and SP-C mRNA levels following the release of a TO are variable, differ between the proteins and are closely related to the changes in lung liquid volumes. We conclude that the re-expression of surfactant proteins following TO is variable and that the change in lung liquid volume is potentially a good indicator for surfactant protein re-expression. Experimental Physiology (2001) 86.1, 55-63.
气管阻塞（TO）诱导的胎儿肺扩张增加是胎儿肺生长的有力刺激，但会迅速降低表面活性蛋白（SP）mRNA水平。我们的目的是确定解除TO后胎儿肺组织中表面活性蛋白重新表达的时间进程，并将其与肺液体积的变化相关联。将胎羊分为以下几组：（1）未处理（对照组）；（2）TO处理4天；（3）TO处理4天，然后解除阻塞24小时；（4）TO处理4天，然后解除阻塞3天。TO处理4天使肺液体积从26.8±1.9增加到72.0±5.6 ml·kg⁻¹，并将SP-A、SP-B和SP-C mRNA水平分别降至对照值的38.5±10.7%、56.8±10.3%和18.3±5.3%。解除TO后1天，肺液体积降至17.4±5.3 ml·kg⁻¹（对照组128天，31.0±3.8 ml·kg⁻¹），SP-A和SP-B mRNA水平与对照水平无差异。相比之下，SP-C mRNA水平仅升至对照的45.4±17.3%。解除TO后3天，肺液体积增加至48.0±8.5 ml·kg⁻¹，SP-A和SP-B mRNA水平分别降至对照的48.8±10.2%和71.5±19.8%；SP-C mRNA水平维持在对照的35.3±12.3%。解除TO后，SP-A、SP-B和SP-C mRNA水平与肺液体积密切负相关。基于这些关系，在该年龄的胎儿中，等同于100%表达的肺液体积远小于对照肺体积（<10 vs. 30 - 40 ml·kg⁻¹）。因此，解除TO后胎儿肺SP-A、SP-B和SP-C mRNA水平的变化是可变的，不同蛋白质之间存在差异，且与肺液体积的变化密切相关。我们得出结论，TO后表面活性蛋白的重新表达是可变的，肺液体积的变化可能是表面活性蛋白重新表达的良好指标。《实验生理学》（2001年）86.1，55 - 63。
