| Abstrakt: |
Analyses of the fatty acid content and composition of various lung lipids were conducted in rats 1 day, 5 days, and 12 days after birth and in adult animals in order to define more clearly the specific lipid peroxidizing system found in neonatal rat lungs. Lipid peroxidation occurs in the 900×g supernatant fraction of rat lung homogenates in an age-dependent manner independent of the addition of any factor and is maximal at 5 days of age. No lipid peroxidation is evident in similar preparations of either newborn or adult lung tissue. As the animals develop, arachidonic and docosahexaenoic acids, fatty acids which are both highly susceptible to lipid peroxidation in the presence of a suitable catalyst, decrease gradually when measured as the percentage of the total fatty acids in the triglyceride fraction of the lung. The total quantity of triglycerides, however, is significantly lower in lungs from 1-day-old rats than at any other age. The fatty acid composition and total quantity of both lung phospholipids and lung free fatty acids do not show similar changes. Following in vitro incubation of the 900×g supernatant fraction of peroxidizing lung homogenates, an appreciable decrease in the amount of arachidonic and docosa-hexaenoic acid could be detected in lung triglycerides. Less extensive decreases were observed in the phospholipid fraction. No changes in these components were observed in newborn or adult animals. The addition of triarachidonin to the 900×g supernatant fraction of lung homogenates resulted in increased malondialdehyde release at all ages tested while added arachidonic acid increased the formation of malondialdehyde only in 5- and 12-day-old rat lung preparations. The addition of triolein, cholesterol arachidonate, and diarachidonyl phosphatidylcholine had no effect on malondialdehyde formation at any age. The age-dependent lipid peroxidation observed after in vitro incubation of rat lung homogenate preparations, therefore, may result from the relatively high concentration of triglycerides containing polyunsaturated fatty acids present in the neonatal tissue. As the susceptible polyunsaturated fatty acids of lung triglycerides are replaced by less unsaturated species, this activity may diminish concomitantly. [ABSTRACT FROM AUTHOR] |
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