| Abstrakt: |
Labeled choline incorporation into adult rat lung alveolar epithelial cells and adult rat lung fibroblasts in monolayer culture was determined after incubation with insulin (Ins) 10 micrograms/ml, Dexamethasone (Dex) 10(-6)M, or no drug (ND). Incubation periods were 1, 3, 4, and 5 hours. The lecithin (phosphatidyl choline - PC) recovered was separated inot disaturated phosphatidyl choline (DSPC) and unsaturated phosphatidyl choline (USPC). Results expressed as specific activity per hour (see Table) indicate that the incorporation of choline into PC and USPC was greater in fibroblasts (F) than in epithelial cells (E) whether ND, Dex or Ins was present. For incorporation into DSPC, there was no difference between E and F whether ND, Dex or Ins was present. There was significant increase in choline incorporation into PC or USPC for both cell types when Ins was present, whereas there was no difference for either cell type when Dex was present. Insulin significantly increased choline incorporation into DSPC in E cells only. Dex was no different from ND in DSPC incorporation in either cell type. We attribute the greater lecithin synthesis of the F cells to a more rapid increase in cellular structural lipids in the fibroblast cell. Dex had no effect on either cell type possibly from the short-term exposure or possibly because the effect of dexamethasone on alveolar epithelial cells is mediated by product(s) from other lung cells, and thus requires a mixed cell culture to have its effect. We suggest that further study of isolated homogeneous cell lines will not be fruitful in the evaluation of mechanisms of acceleration of lung maturation. |
