| Abstract: | The ability of the lungs to release fatty acids from circulating triglycerides or lipoproteins for its own phospholipid synthesis may be one of the factors which limit the rate of surfactant formation. Therefore, the development of the lipolytic activity of lungs obtained from late fetal and neonatal rabbits has been studied and the results correlated to the phospholipid content of lungs of similar ages. Isolated lungs were perfused with a medium which contained cold and radioactive triglyceride, and the release of fatty acids into the perfusion medium was analyzed by both colorimetric and radiochemical methods. The phospholipids of the postmitochondrial supernatant fractions of the lungs were extracted and quantified by measuring inorganic phosphorus. Finally, the influence of maternal cigarette smoke exposure on the lipolytic activity of the lungs of their litters were studied. A high lipolytic activity in the lungs of 28-day-old fetuses was detected. The activity decreased towards birth, and was lowest on the first day after birth (about 20% of that observed in 28-day-old fetuses). However, it increased again during the first week after birth. Exposure of the mothers to cigarette smoke during the last 10 days before delivery did not affect the pulmonary lipolytic activity of the offspring. Although the lung phospholipid content increased 3.6-fold from 28 days of fetal life to 1 week after birth, it remained unchanged on the days when the lung lipolytic activity was lowest. We conclude that changes in lung lipolytic activity influence lung phospholipid synthesis, and consequently influence also surfactant formation in the lungs. |
