Dobbs L G, Mason R J
Am Rev Respir Dis. 1978 Oct;118(4):705-33. doi: 10.1164/arrd.1978.118.4.705.
Alveolar type II synthesize and secrete pulmonary surface-active material; the stimuli for secretion in vivo and the mechanisms by which secretion occurs are not well understood. We studied the secretion of disaturated phosphatidylcholine, the principal component of surfactant, from a purified population of type II cells. We isolated type II type from the lungs of adult male rats by treatment with trypsin, centrifugation over discontinuous density gradients, and adherence in primary culture; our preparations were 93 +/- 5 per cent (mean +/- SD; n = 10) type II cells. Basal secretion was 2.9 +/- 1.0 per cent (n = 16) of total cellular carbon-14 [14C]-disaturated phosphatidycholine in 3 hours. We found that 10(-8) M 12-O-tetradecanoyl-13-phorbol-acetate (TPA), a substance that has been shown to stimulate secretion in other cell systems, caused a release of 14C-disaturated phosphatidylcholine that was 8.4 times the basal rate. TPA caused a greater release of disaturated phosphatidylcholine than did any other substance that we have tested. Low temperature (4 degree C) inhibited the basal release by 85 per cent and the TPA-stimulated release by 98 per cent. The effect of TPA was also inhibited 25 per cent by 10(-6) M colchicine and 33 per cent by 10(-5) M vinblastine. Medium from control cells contained 6.3 +/- 1.3 per cent (mean +/- SD; n = 5) of total cellular lactate dehydrogenase (a marker for cell damage) after a 3-hour incubation period; medium from cells treated with TPA contained a similar amount, 6.7 +/- 1.5 per cent (n = 5). We concluded that the TPA-induced secretion of disaturated phosphatidylcholine is an active process probably mediated by microtubules. Because it has a large stimulatory effect on secretion, TPA may be useful for the study of the mechanisms by which surfactant is secreted.
II型肺泡细胞合成并分泌肺表面活性物质；其在体内的分泌刺激因素以及分泌发生的机制尚未完全明确。我们研究了II型细胞纯化群体中表面活性剂的主要成分——二饱和磷脂酰胆碱的分泌情况。我们通过用胰蛋白酶处理、在不连续密度梯度上离心以及在原代培养中贴壁的方法，从成年雄性大鼠的肺中分离出II型细胞；我们的制备物中II型细胞占93±5%（平均值±标准差；n = 10）。基础分泌量在3小时内为总细胞碳-14[¹⁴C] - 二饱和磷脂酰胆碱的2.9±1.0%（n = 16）。我们发现，10⁻⁸M 12 - O - 十四烷酰佛波醇 - 13 - 乙酸酯（TPA），一种已被证明能在其他细胞系统中刺激分泌的物质，导致¹⁴C - 二饱和磷脂酰胆碱的释放量是基础速率的8.4倍。TPA引起的二饱和磷脂酰胆碱释放量比我们测试的任何其他物质都要大。低温（4℃）抑制基础释放85%，抑制TPA刺激的释放98%。TPA的作用也被10⁻⁶M秋水仙碱抑制25%，被10⁻⁵M长春碱抑制33%。在3小时的孵育期后，对照细胞的培养基中含有总细胞乳酸脱氢酶（细胞损伤标志物）的6.3±1.3%（平均值±标准差；n = 5）；用TPA处理的细胞的培养基中含有相似的量，即6.7±1.5%（n = 5）。我们得出结论，TPA诱导的二饱和磷脂酰胆碱分泌是一个可能由微管介导的活跃过程。由于它对分泌有很大的刺激作用；TPA可能有助于研究表面活性剂分泌的机制。
