Ikegami M, Horowitz A D, Whitsett J A, Jobe A H
Pulmonary Biology, Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA.
Am J Physiol. 1998 Jun;274(6):L933-9. doi: 10.1152/ajplung.1998.274.6.L933.
Surfactant protein (SP) C metabolism was evaluated in vivo by measurements of the clearance of bovine native SP-C (nSP-C) and a recombinant SP-C (rSP-C) in rabbits and mice and in vitro by the uptake into MLE-12 cells. rSP-C is the 34-amino acid human sequence with phenylalanine instead of cysteine in positions 4 and 5 and isoleucine instead of methionine in position 32. Alveolar clearances of iodinated SP-C and rSP-C after tracheal instillation were similar and slower than those for dipalmitoyl phosphatidylcholine (DPC) in the rabbit. nSP-C and rSP-C were cleared from rabbit lungs similarly to DPC, each with a half-life (t1/2) of approximately 11 h. In mice, the clearance of rSP-C from the lungs was slower (t1/2 28 h) than the clearance of DPC (t1/2 12 h). Liposome-associated dinitrophenyl-labeled rSP-C was taken up by MLE-12 cells, and the uptake was inhibited by excess nSP-C. The pattern of inhibition of dinitrophenyl-rSP-C uptake by SP-B, but not by SP-A, was similar to that previously reported for nSP-C. Clearance kinetics of nSP-C were similar to previous measurements of pulmonary clearance of SP-B in rabbits and mice. rSP-C has clearance kinetics and uptake by cells similar to those of nSP-C.
通过测量兔和小鼠体内牛天然表面活性蛋白C（nSP-C）和重组表面活性蛋白C（rSP-C）的清除率，以及体外MLE-12细胞对其摄取情况，对表面活性蛋白（SP）C的代谢进行了评估。rSP-C是由34个氨基酸组成的人类序列，第4和第5位的半胱氨酸被苯丙氨酸取代，第32位的甲硫氨酸被异亮氨酸取代。气管内滴注碘化SP-C和rSP-C后，兔肺泡清除率相似，且比二棕榈酰磷脂酰胆碱（DPC）的清除率慢。nSP-C和rSP-C从兔肺中的清除情况与DPC相似，半衰期（t1/2）均约为11小时。在小鼠中，rSP-C从肺中的清除速度比DPC慢（t1/2为28小时，而DPC的t1/2为12小时）。脂质体相关的二硝基苯基标记的rSP-C被MLE-12细胞摄取，过量的nSP-C可抑制这种摄取。SP-B而非SP-A对二硝基苯基-rSP-C摄取的抑制模式与先前报道的nSP-C相似。nSP-C的清除动力学与先前在兔和小鼠中测量的SP-B肺清除情况相似。rSP-C的清除动力学和细胞摄取情况与nSP-C相似。
