Zhou H, Gao Y, Raj J U
Department of Pediatrics, Harbor-UCLA Medical Center, University of California, Los Angeles, School of Medicine, Torrance 90509, USA.
J Appl Physiol (1985). 1996 Feb;80(2):390-6. doi: 10.1152/jappl.1996.80.2.390.
Antenatal glucocorticoid therapy improves pulmonary function in preterm newborns. We have determined the effect of antenatal glucocorticoid therapy on nitric oxide-mediated relaxation in pulmonary vessels of preterm lambs. Ovine fetuses (126 days gestation; full term = 150 days) were injected with betamethasone (0.5 mg/kg body wt) or saline. After 48 h, lambs were delivered, ventilated for 3 h, and killed. Isolated fourth-generation pulmonary arteries (2-3 mm diameter) and veins (1.5-2 mm diameter) were suspended in organ chambers filled with modified Krebs-Ringer solution (95% O2-5% CO2) at 37 degrees C, and their isometric tension was recorded. During contractions to endothelin-1 or U-46619 (in the presence of indomethacin), acetylcholine and bradykinin induced endothelium-dependent nitro-L-arginine-inhibitable relaxation in arteries and veins. The relaxation was greater in veins of betamethasone-treated than in those of control lambs. Veins from lambs without endothelium treated with betamethasone were more sensitive to sodium nitroprusside than veins from controls. For arteries, there was no significant difference in relaxation between different groups. Relaxation induced by 8-bromoguanosine 3',5'-cyclic monophosphate was similar in arteries and veins of different groups. Radioimmunoassay showed that nitric oxide caused a greater increase in guanosine 3',5'-cyclic monophosphate in betamethasone-treated veins than in controls. These data suggest that antenatal betamethasone therapy augments nitric oxide-mediated relaxation of pulmonary veins of preterm lambs, probably by increasing soluble guanylate cyclase activity of vascular smooth muscle.
产前糖皮质激素治疗可改善早产儿的肺功能。我们已经确定了产前糖皮质激素治疗对早产羔羊肺血管中一氧化氮介导的舒张作用的影响。给妊娠126天（足月为150天）的绵羊胎儿注射倍他米松（0.5mg/kg体重）或生理盐水。48小时后，娩出羔羊，通气3小时后处死。将分离出的第四代肺动脉（直径2 - 3mm）和静脉（直径1.5 - 2mm）悬挂于充满改良克雷布斯-林格溶液（95% O₂ - 5% CO₂）的器官浴槽中，于37℃记录其等长张力。在内皮素-1或U - 46619收缩过程中（存在吲哚美辛时），乙酰胆碱和缓激肽可诱导动脉和静脉产生内皮依赖性、硝基-L-精氨酸可抑制的舒张。倍他米松治疗组羔羊静脉的舒张程度大于对照组。倍他米松处理的无内皮羔羊的静脉对硝普钠比对照组更敏感。对于动脉，不同组之间的舒张无显著差异。不同组的动脉和静脉中8-溴鸟苷3',5'-环磷酸诱导的舒张相似。放射免疫分析表明，一氧化氮使倍他米松治疗组静脉中的鸟苷环磷酸增加幅度大于对照组。这些数据表明，产前倍他米松治疗增强了早产羔羊肺静脉中一氧化氮介导的舒张，可能是通过增加血管平滑肌的可溶性鸟苷酸环化酶活性实现的。
