Lung development in the chick embryo. I. Phosphatidylcholine synthesis in the developing chick lung
Related Experiment Videos
Insights
This study shows that both phosphatidylcholine (PC) synthesis pathways in developing chick lungs change significantly. Neither pathway dominates, and increased PC synthesis near hatching correlates with lung development and surfactant appearance.
Area of Science:
- Biochemistry
- Developmental Biology
- Pulmonary Physiology
Background:
- Phosphatidylcholine (PC) is a crucial component of pulmonary surfactant.
- Understanding PC synthesis pathways is vital for lung development research.
Purpose of the Study:
- To investigate the relative contributions of the choline and phosphatidylethanolamine pathways to PC synthesis in developing avian lungs.
- To correlate PC synthesis with lung maturation and surfactant production.
Main Methods:
- Incubation of chick lung tissue at different developmental stages with radiolabeled precursors ([3H]methionine and [14C]choline).
- Separation and quantification of phosphatidylcholine using thin-layer chromatography and liquid scintillation counting.
- Analysis of PC synthesis rates via the two main pathways.
Main Results:
- Both PC synthesis pathways showed a decline from day 12 to day 16 of incubation, followed by an increase.
- Neither the choline nor the phosphatidylethanolamine pathway predominated throughout lung development or post-hatching.
- Significant differences in pathway activity were observed on specific incubation days (14, 18, 19).
- Increased PC synthesis correlated with the appearance of lamellar bodies and surfactant.
Conclusions:
- Avian lung PC synthesis involves dynamic contributions from both pathways, without a consistent dominance.
- The observed increase in PC synthesis late in development is linked to the maturation of lung epithelial cells and surfactant system formation.
- These findings offer insights into pulmonary surfactant biogenesis in developing birds.
Abstract:
We investigated the relative contribution of the two pathways of phosphatidylcholine (PC) synthesis in lungs from chick embryos of 12 to 20 days of incubation as well as from hatched chicks and adult chickens. Lung "blocks" were incubated for 60 min in vitro in the presence of [3H]methionine and [14C]choline. PC was separated by thin-layer chromatography, and the amount of labeled product was determined by liquid scintillation counting. PC synthesis (expressed as pmoles PC per mg protein per 60 min) by the choline pathway declined from the 12-day value of 40 to a minimum of 8 at day 16 and then rose gradually to a peak of 74 on day 1 posthatching. PC synthesis via the phosphatidylethanolamine pathway also declined from day 12 (54) to day 16 (13) but peaked on day 19 (65) and again on day 1 posthatching (54). Synthetic activities of the two pathways differed significantly (P less than or equal to 0.05) only on days 14, 18, and 19 of incubation. Unlike the mammalian lung, neither pathway seems to predominate throughout incubation or after hatching. The increase in PC synthesis towards the end of incubation correlates with the time of appearance of lamellar bodies in the lung epithelial cells and of surfactant in the airways.