Johnsson H, Eriksson L, Sedin G
Department of Women's and Children's Health, Uppsala University, SE-751 85 Uppsala, Sweden.
Pediatr Res. 2001 Apr;49(4):566-71. doi: 10.1203/00006450-200104000-00020.
Maternal treatment with corticosteroids before preterm delivery is effective in reducing the incidence of respiratory distress syndrome and neonatal mortality. We hypothesized that corticosteroids might lower the lung hyaluronan concentration. Twenty-five rabbit dams (term = 31 d) with timed pregnancies were injected s.c. with 0.75 mg of betamethasone or saline (controls) 1 d before delivery. In addition, two dams delivered at 25 d of gestation were injected with 0.75 mg of betamethasone on two consecutive days before delivery. A total of 238 live pups were delivered by preterm cesarean section at 25, 27, 28, or 29 d of gestation and killed immediately. Their lung hyaluronan concentrations were measured with a radiometric assay, and wet/dry lung weight ratios were determined. Lungs of rabbit pups exposed antenatally to betamethasone and delivered at 25 or 27 d of gestation, but not at 28 or 29 d, displayed significantly (p = 0.001 and p = 0.008, respectively) lower hyaluronan concentrations than control pups, accompanied by less intense subepithelial staining for hyaluronan in alveolar walls. There was no significant difference in wet/dry lung weight ratio between pups exposed to one dose of betamethasone and controls. Antenatal corticosteroid exposure lowers the lung hyaluronan concentration in preterm rabbit pups delivered at 25 or 27 d of gestation, but not in those delivered at 28 or 29 d.
早产前对母体使用皮质类固醇可有效降低呼吸窘迫综合征的发生率和新生儿死亡率。我们推测皮质类固醇可能会降低肺透明质酸浓度。对25只怀孕时间确定的兔母（孕期为31天）在分娩前1天皮下注射0.75毫克倍他米松或生理盐水（对照组）。此外，对2只在妊娠25天分娩的母兔在分娩前连续两天注射0.75毫克倍他米松。总共238只活幼崽在妊娠25、27、28或29天通过早产剖宫产分娩，并立即处死。用放射性测定法测量它们的肺透明质酸浓度，并测定肺湿/干重比。产前暴露于倍他米松且在妊娠25或27天分娩（而非28或29天）的兔幼崽肺透明质酸浓度显著低于对照幼崽（分别为p = 0.001和p = 0.008），同时肺泡壁上皮下透明质酸染色强度较低。接受一剂倍他米松的幼崽与对照幼崽的肺湿/干重比无显著差异。产前暴露于皮质类固醇可降低妊娠25或27天分娩的早产兔幼崽的肺透明质酸浓度，但对妊娠28或29天分娩的幼崽则无此作用。
