Related Experiment Videos
Phosphatidylcholine-lysophosphatidylcholine cycle pathway enzymes in rabbit lung. II. Marked differences in the
Insights
Pulmonary phosphatidylcholine (PC) synthesis involves enzymes from both the CPD-choline and PC-lysophosphatidylcholine (lysoPC) pathways. The PC-lysoPC pathway enzymes significantly increase during fetal rabbit lung development and at birth, suggesting their crucial role in maturation.
Area of Science:
- Biochemistry
- Pulmonary Medicine
- Developmental Biology
Background:
- Phosphatidylcholine (PC) is vital for lung surfactant.
- The PC-lysophosphatidylcholine (lysoPC) cycle is a potential pathway for PC synthesis.
- Enzyme activities in fetal rabbit lung development require characterization.
Purpose of the Study:
- To quantify enzymes of the PC-lysoPC cycle and CPD-choline pathways in developing fetal rabbit lungs.
- To compare the developmental profiles of these two pathways.
- To elucidate the role of the PC-lysoPC pathway in pulmonary maturation.
Main Methods:
- Enzyme assays for choline kinase (CK), phosphorylcholine cytidyl transferase (CyT), phosphorylcholine glyceride transferase (PCGT), lysophospholipase (LPL), lysophosphatidylcholine-lysophosphatidylcholine acyltransferase (LAT), and acyl-CoA LAT.
- Analysis of lung homogenates from fetal, newborn, and adult rabbits.
- Measurement of total lung phospholipid and protein content.
Main Results:
- Enzymic activities of the CPD-choline pathway (CK, CyT, PCGT) decreased significantly with gestational age.
- Activities of PC-lysoPC cycle enzymes (LPL, LAT, acyl-CoA LAT) increased markedly with gestational age, showing 4-10 fold increases from early gestation to the newborn stage.
- These findings indicate a shift towards the PC-lysoPC pathway during lung maturation.
Conclusions:
- The PC-lysoPC cycle pathway appears to play a critical role in regulating pulmonary PC synthesis and turnover during fetal development and at birth.
- Enzyme activity profiles suggest the PC-lysoPC pathway becomes dominant as the fetal lung matures.
- Further research into the PC-lysoPC pathway is warranted for understanding lung development and surfactant homeostasis.
Abstract:
Lysophosphatidylcholine (lysoPC), a breakdown product of phosphatidylcholine (PC), might be important in pulmonary PC synthesis through fatty acid exchange reactions. This study defines the levels of three of the enzymes of the PC-lysoPC cycle pathway (lysophospholipase (LPL) (EC. 3.1.1.5), lysophosphatidylcholine-lysophosphatidylcholine acyltransferase (LAT), and acyl-CoA lysophosphatidylcholine acyltransferase (acryl-CoA LAT) (EC. 2.3.1.23)) in developing fetal rabbit lung and compared them with the enzymes of the CPD-choline synthetic pathway (choline kinase (CK) (EC. 2.7.1.32), phosphorylcholine cytidyl transferase (CyT) (EC. 2.7.7.15), and phosphorylcholine glyceride transferase (PCGT) (EC. 2.7.8.2). Lung homogenates of fetal rabbits of known gestation, newborn, and adult rabbits were used for the enzyme, protein, and phospholipid analyses. Total lung phospholipid, PC, and protein increased with gestational age. Thirty days' gestation, newborn, and maternal lung activities of CK, CyT, and PCGT had decreased to only 50% of their activities at 22-26 days' gestation. In contrast, LPL and LAT activities increased 4-5-fold from 22-26 days to 30 days' gestation, and increased further in the newborn lung, finally to a level matching maternal lung (about 8-10-fold higher than the 22-26 days' gestation activities). The microsomal acyl-CoA LAT also showed a similar increasing activity with gestational age. In fetal lung, enzymic activities for the apparent major PC synthetic pathway decreased. In contrast, the marked increases in LPL, LAT, and acyl-CoA LAT activities with increasing gestational age and at birth suggests importance of the PC lysoPC cycle pathway in regulating synthesis and turnover with maturation.