Homeoviscous adaptation in turtle lung surfactant

Lau, Ming-Jarm. (1978) Homeoviscous adaptation in turtle lung surfactant. Masters thesis, Memorial University of Newfoundland.

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Abstract

To determine if homeoviscous adaptation occurs in lung surfactant of an air-breathing ectotherm so as to maintain a specific physical state critical for function at different temperatures, map turtles were acclimated to 5, 14, 22, and 32°C for at least one month. Lipid analyses were carried out with lung lavage fluid and lung tissue using thin layer chromatography and gas-liquid chromatography. – Whereas phospholipid content per g of fresh lung tissue in lavage fluid was significantly elevated at 32°C as compared to 5 and 14°C, no significant differences were observed in phospholipid content in lung tissue with changing temperature. Lecithin was the major phospholipid in lavage fluid, constituting more than 70% of total phospholipid, and it increased with increasing temperature. The two major phospholipids, in lung, phosphotidylcholine and phoshatylethanolamine showed changes with temperature and trends which were complementary to each other. There was a proportionate increase in palmitate and decrease in palmitoleate content in both total lipid and Phosphatidylcholine in lavage fluid. The changes in palmitate content in lavage fluid were not reflective of a general increase of the corresponding fatty acid in the lipids of lung. A significant increase in saturation was found in total lipid and phosphatidylcholine of lavage fluid, and phosphatidylcholine and phosphatidylethanolamine in lung. Saturated lecithin isolated from total lavage had a fatty acid profile consisting primarily of palmitate, 85 mole%. Saturated lecithins, principally dipalmitoyl lecithin, increased as a proportion of lavage lecithin with increasing body temperature. Thermograms of model lecithin mixtures approximating the lecithins in lavage from turtles kept at 5 and 32°C showed a shift in transition temperature, implying the difference in dipalmitoyl phosphatidylcholine content in the lipids resulted in a change in physical state. These finding were consistent with the preservation of a constant specific phase(s) in surfactant lipid at each temperature of acclimation.

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