培養肺胞II型細胞の燐脂質の代謝と細胞内構造に及ぼす高濃度酸素の効果

Effects of hyperoxia on phospholipid metabolism and on intracellular structure of cultured type II pneumocytes

　大気中および100％酸素中で生後6日間飼育したラット（air-ratおよびO₂-rat）の肺から肺胞II型細胞を分離培養し，培養中（24時間）の燐脂質の代謝と細胞内微細構造に及ぼす高濃度酸素（95％）の効果について調べた。高濃度酸素により，air-ratとO₂-ratの細胞でcholineから生成される総PC量は71.64％と71.63％に減少し，O₂-ratの細胞から分泌される総PC量も75.88％に減少し，air-ratの細胞内DSPCの比率も74.92％から64.2％に低下した。Glycerolの細胞内とりこみは，O2-ratの細胞を95％空気中と95％酸素中で培養したとき，それぞれ28.91％と23.37％に減少し，細胞内に分泌される総燐脂質量もそれぞれ53.63％と60.24％に低下した。Glycerolから生成される燐脂質の中でPCの比率はair-ratの細胞において70.52％から60.29劣に低下し，培養液中では58.58％から51.24％に低下した。PCの生成の減少にともない，他の燐脂質の生成と分泌の増加がみられた。O₂-ratの細胞から分泌されるPCの比率は95％空気中と95％酸素中の培養でそれぞれ26.22％と28.52％であった。高濃度酸素によって培養中の細胞の総蛋白質量は78.88％〜87.01％に減少し，DNA量は54.28〜50.74％に減少した。Air-ratの細胞を95％酸素中で培養した時，tight junctionの消失，グリコーゲン顆粒の減少，細胞質内の空胞形成，ミトコンドリアの円形化と膜の平滑化と内部構造物の密度の減少，endoplasmic reticulumの変形，micro villiの変形等の微細構造の変化がみられた。高濃度酸素から発生するfree radicalsはラット新生児肺において，肺胞II型細胞の細胞内構造を損傷し，燐脂質，蛋白質，核酸の代謝を抑制し，肺surfactantの活性を変えるものと思われる。

Alveolar type II cells isolated from the lung of 6 days old rats fed in air (air-rat) and in 100% O₂ (O₂-rat) for 6 days after birth were used to observe the effects of oxygen of 95%-100% on phospholipid metabolism and intracellular structure for 24 hrs in culture. Total PC synthesis from choline in the cells of air-and O₂-rat was decreased to 77.64% and 71.33% by 95% O₂. After the culutre of the cells of O₂-rat in 95% air and 95% O₂, the incorporation of glycerol into phospho-lipid of the cells was reduced to 28.91% and 23.37%, respectively, and the release of total phospholipid was also reduced to 53.63% and 60. 29%. The ratio of PC in the cells of air-rat was decreased from 58.58% to 51.24%. In accordance with the alteration of PC syn-thesis in the cells by O₂ treatment, the ratio of other phospholipids, such as PA, LPC, CL, was increased. The ratio of PC released from the cells of O₂-rat was 26. 22% and 28. 52% in culture of air and O₂, respe-ctively. The total protein concentration of dishes in culture was decreased to 78.88%-87.01% by O₂ treat-ment. DNA concentration was also eliminated to 54.28 %-50.74% by O₂ treatment. The intracellular strucutre was altered by O₂ treatment, i.e. loss of tight junctions, change of micro villi, loss of density of glycogen gra-nules, vacuolation in cytoplasm, smoothed membraneof mitochondria, loss of density of intra-mitochondrial structure, especially the destruction of endoplasmic reticulum where PC of surfactant is synthesized. The free radicals produced from O₂ may alter the surface activity of lung by disrupting phospholipid synthesis in type II pneumocytes and by impairing the cellular structure.