title: Characterization of the extracellular bactericidal factors of rat alveolar lining material.
abstract: The surfactant fraction (55,000-g pellet) of leukocyte-free rat bronchoalveolar lavage fluid contains factors that rapidly kill and lyse pneumococci. These factors were purified and identified biochemically by using a quantitative bactericidal test to monitor fractionation procedures. 91% of the antipneumococcal activity of rat surfactant was recovered in chloroform after extraction of rat surfactant with chloroform-methanol (Bligh-Dyer procedure). After chromatography on silicic acid with chloroform, acetone, and methanol, all detectable antibacterial activity (approximately 80% of the initial activity) eluted with the neutral lipids in chloroform. When rechromatographed on silicic acid with hexane, hexane-chloroform, and chloroform, the antibacterial activity eluted with FFA. Thin-layer chromatography (TLC) established that the antibacterial activity was confined to the FFA fraction. Gas-liquid chromatography showed that the fatty acid fraction contained a mixture of long-chain FFA (C12 to C22) of which 66.7% were saturated and 32.4% were unsaturated. The quantity of TLC-purified FFA needed to kill 50% of 10(8) pneumococci under standardized conditions (one bactericidal unit) was 10.6 +/- 0.5 micrograms. Purified FFA acted as detergents, causing release of [3H]choline from pneumococcal cell walls and increased bacterial cell membrane permeability, evidenced by rapid unloading of 3-O-[3H]methyl-D-glucose. FFA acting as detergents appear to account for the bactericidal and bacteriolytic activity of rat pulmonary surfactant for pneumococci.
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents; D001433:Bacteriolysis; D002463:Cell Membrane Permeability / Q000187:drug effects; D004285:Dogs; D005230:Fatty Acids, Nonesterified / Q000302:isolation & purification / Q000494:pharmacology; D006168:Guinea Pigs; D008066:Lipolysis; D008297:Male; D011510:Proteolipids / Q000302:isolation & purification* / Q000502:physiology; D011650:Pulmonary Alveoli / Q000502:physiology*; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000302:isolation & purification* / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D013296:Streptococcus pneumoniae / Q000187:drug effects / Q000254:growth & development; D007507:Therapeutic Irrigation
chemical_list: D000900:Anti-Bacterial Agents; D005230:Fatty Acids, Nonesterified; D011510:Proteolipids; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants