報告書番号

U88069

タイトル（和文）

石炭灰吸入が肺胞マクロファージの代謝活性に与える影響

タイトル（英文）

Effects of coal fly ash inhalation on enzyme activities in the pulmonuary alveolar macrophage.

概要 （図表や脚注は「報告書全文」に掲載しております）

本研究は、肺内遊出細胞の持つ異物の貪食と排出という生体防御機能が、石炭灰の吸入によってどのように変化するかを明らかにする目的で、5 mg/m3の濃度で10日間の暴露実験を行い、肺胞マクロファージ（AM）の貪食能に関与する酵素活性の経時的変化について検討したものである。
その結果、貪食能に関与する酵素の活性は一時的に低下するものの1日目以降は活性が増加し、7日目以降は肺全体としては貪食と排出の能力が昂進された状態が続くことが明らかになった。それは、粒子の吸入にともない貪食や排出を行った結果、曝露初期に肺内に存在したAMは相対的に貪食能が低下し、次いで新たに活性の高いAMが、細胞分裂や遊出によって肺内に供給された結果によるものと考えられた。従って、実際の環境レベルにおいても、肺全体としては石炭灰の吸入に対する防御作用が機能するという生体メカニズムが示唆された。

概要 （英文）

Alveolar macrophage (AM) phagocytizes irritants inhaled into the lung alveoli. Phagocytic activity of AM depends upon energy-generating system including oxidative phsphorylation and glycolytic pathway in the cell. Purpose of this paper is to clarify changes of marker enzyme activities in the system during particle inhalation exposures in vivo.
Forty eight male golden hamsters were exposed to coal fly ash at 5 mg/m3, 20 hours per day, for 10 days, and the same number of animals was served as control. Animals were sacrificed at 1, 4, 7, and 10 days after initiation of the exposure. The lungs were lavaged, and the lavage fluid was centrifuged to collect lung free cells and surfactant. The lavage was examined whether or not the lung inflammation and impairment occurred. Recovered cells were stained to classify the leukocyte differentials. Most of the recovered cells in both groups were AM. In 4-day and 10-day exposed groups, about half and four-fifths of recovered cells were fly ash laden-AM, respectively.
Activities of two marker enzymes, lactate dehydrogenase and acid phosphatase, and protein contents in the lavage from both groups showed no evidence of inflammation in the lung. Specific activity of succinate cytochrome c reductase (SCR) in AM was measured as a maker of oxidative-phosphorylation. Activity of pyruvate kinase (PK) that is a rate limiting enzyme of glycolytic pathway was also measured. Furthermore, glucose 6-phosphate dehydrogenase (G6PDH), a key enzyme in hexose monophosphate shunt, was evaluated for the activation of the AM.
SCR activity in the AM from exposed animals was 1.4-fold to that of the control animals at the termination of exposure. PK activity decreased at 1-day; then it increased after 4 days of exposure. The activity reached 1.3-fold of the control group at 7- and 10-day exposure. Activity of G6PDH also changed in the same manner as the PK. In addition, marker enzyme activity of AM phagocytosis in the whole lung showed increase compared to the control. These results suggested that the newly activated AM was supplied in the exposed lung with cell division or infiltration during coal fly ash exposure.

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