ラット肺サーファクタソト蛋白質D(SP-D)の特性とその精製
スポンサーリンク
概要
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Native surfactant protein D(SP-D) was isolated from the supernatant of rat lung lavage fluids after overnight centrifugation at 33,000Xgav by affinity column chromatography with mannose-Sepharose 6B. Since SP-D possesses similarities to SP-A, which is the main component of surfactant proteins, in collagen-like structure and carbohydrate binding property, the effect of SP-D upon surfactant secretion from alveolar type II cells was investigated and compared with that of SP-A. SP-A inhib- ited surfactant secretion from type II cells, whereas native SP-D could inhibit neither the basal secretion nor the facillitated secretion. However, native SP-D reduced the inhibitory effect of SP-A on surfactant secretion in a dose dependent manner. Native SP-D competed with ???I-SP-A for high affinity binding to type II cells. The butanol-soluble materials extracted from native SP-D possessed the ability to reduce the activity of SP-A on surfactant secretion as much as native SP-D. On the other hand, butanol-extracted SP-D could neither inhibit the activity of SP-A on surfactant secre- tion from type II cells nor compete with 125I-SP-A for binding to type II cells. ???I-SP-A bound native SP-D, but not butanol-extracted SP-D. These data indicate that the butanol soluble mate- rials extracted from native SP-D are essential for the effect of native SP-D upon the activity of SPA. Analysis of SP-D by high-performance liquid chromatography demonstrated that materials extractable with butanol were associated with native SP-D. The butanol-soluble materials consisted of mainly phospholipids with phosphatidylcholine accounting for 84.8% of the phospholipids associat- ed with SP-D. The native SP-D was then further purified by adsorption with barium sulfate, elution with sodium citrate and removal of possible contamination of SP-A, followed by delipidation with 1-butanol. The contents of SP-D and SP-A in lung lavage fluids and lung homogenates were determined by enzyme-linked immunosorbent assay using anti-rat SP-D and anti-rat SP-A IgG. 99.1% of SP-A was present in the 33,000Xg pellet, whereas 71.1% of SP-D was in the 33,000Xg supernatant. The total content of SP-D was 12.3% and 22.0% of that of SP-A in lavage fluids and lung homogenates, respectively. The present study demonstrates that SP-D alters SP-A activity on type II cells through the interaction of SP-D with SP-A via SP-D associated lipids and that SP-D is distributed differently from SP-A in the rat lung.
- 札幌医科大学の論文
- 1991-08-01
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