O'Brodovich H M, Mullen B, Hannam V L, Goodman B E
Department of Paediatrics, Hospital for Sick Children, University of Toronto, ON, Canada.
Can J Physiol Pharmacol. 1997 May;75(5):431-5.
The lung relies upon epithelial active transport of Na+ to aid in the clearance of fluid from its air spaces. Because it is unknown whether the rate of active Na+ transport by the distal lung epithelium varies during early postnatal age, we performed studies in young guinea pigs (7 and 30 days after birth). We used a single pass isolated perfused lung model in which a Krebs Ringer bicarbonate solution containing 22Na+, [14C]sucrose, and FITC-dextran was placed into the air spaces of the lungs, and apparent permeability-surface area (PS) products were calculated after determining the changes in lung weight and the concentrations of the isotopes in the vascular effluent. The PS product for 22Na+, but not [14C]sucrose, decreased significantly at both ages when amiloride was infused (final concentration of 10(-4) M). Amiloride also decreased the rate of fluid clearance, as assessed by changes in organ weight, at both ages. Although the absolute rate of amiloride-sensitive 22Na+ transport increased with age, morphometric measurement of the alveolar region demonstrated that the rate of amiloride-sensitive 22Na+ transport per unit alveolar surface area was similar. These data indicate that although the guinea pig lung undergoes significant growth shortly after birth, the rate of amiloride-sensitive active Na+ transport per unit surface area remains constant. Since a component of weight loss was insensitive to amiloride, these in vivo studies suggest that the amiloride-insensitive Na+ transport pathways previously identified in cultured lung epithelium exist in the intact lung.
肺依靠上皮细胞对钠离子的主动转运来协助清除肺泡腔中的液体。由于目前尚不清楚出生后早期远端肺上皮细胞对钠离子的主动转运速率是否会发生变化，我们对幼年豚鼠（出生后7天和30天）进行了研究。我们使用了单通道离体灌注肺模型，将含有22Na+、[14C]蔗糖和异硫氰酸荧光素标记葡聚糖的碳酸氢盐林格氏液注入肺的气腔中，并在测定肺重量变化和血管流出液中同位素浓度后计算表观通透率-表面积（PS）乘积。当注入氨氯吡咪（终浓度为10(-4) M）时，两个年龄段的22Na+的PS乘积均显著下降，但[14C]蔗糖的PS乘积未下降。氨氯吡咪在两个年龄段也均降低了液体清除率，这通过器官重量变化来评估。尽管氨氯吡咪敏感的22Na+转运的绝对速率随年龄增加，但对肺泡区域的形态学测量表明，单位肺泡表面积的氨氯吡咪敏感的22Na+转运速率相似。这些数据表明，尽管豚鼠肺在出生后不久会经历显著生长，但单位表面积的氨氯吡咪敏感的主动钠离子转运速率保持恒定。由于体重减轻的一部分对氨氯吡咪不敏感，这些体内研究表明，之前在培养的肺上皮细胞中鉴定出的对氨氯吡咪不敏感的钠离子转运途径在完整肺中也存在。
