Summary: Labeled choline incorporation into adult rat lung type II alveolar epithelial cells and adult rat lung fibroblasts in monolayer culture was dgtennined after incubation with insulin (Ins) 10 μg/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 into disaturated phosphatidyl choline (DSPC) and unsaturated phasphatidyl choline (USPC). Results expressed as specific activity per hour (see Table) indicate that the incorporatian 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 strucrural lipids in the fibroblast cell. Dex had no effect an either cell type 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 vill not be fruitful in the evaluation of mechanisms of acceleration of lung maturation. Speculation: Isolated alveolar epithelial cells shw a relatively greater increase in DSPC synthesis than do isolated fibroblasts in response to insulin. while neither cell type responds to short term glucocarticoid treatment. Since other investigators using mixed lung cell cultures have sham increased DSPC in response to insulin end even greater response with glucocarticoid treatment, it is likely that the presence of fibroblasts or other pulmonary cells is required for the alveolar epithelial cell to increase DSPC production in response to glucocorticoids.

An in vitro system for evaluating the toxicity of serum from cystic fibrosis (CF) patients is reported. Rat lung epithelial cells were incubated for 18 hours in medium containing varying concentrations of human serum (HS) from CF patients and patients without cystic fibrosis (non-CF). Twenty-four assays were performed for 4 concentrations of each HS. Attachment efficiency (AE), defined as the number of cells attached to the culture surface divided by the number of cells dispensed per culture, was determined for each concentration of HS. Attachment efficiency was always greater when no human serum was present. As the percentage of serum increased, the AE decreased in all cases.Because the AE varied from day to day, the ratio (RAE) of the AE for 0% HS to the AE for 2% HS was calculated for each serum sample. The RAE value was reproducible within 0.07 over a four-week interval for individual serum samples. The higher the RAE value, the more toxic the serum.There is a significant difference (p < 0.05) in the two populations of patients. The serum from the CF patients was more toxic to rat lung epithelial cells than serum from non-CF patients.