Increased cyclic AMP levels and β-adrenergic antagonist binding in cystic fibrosis fibroblasts

Abstract

We have found that cAMP is induced to a greater extent in cultured cystic fibrosis fibroblast cell lines than in normal lines using a β-adrenergic agonist. By using the potent β-antagonist, [ 3H]dihydroalprenolol in a competitive radioligand binding assay, we measured β-adrenergic specific binding on skin fibroblasts derived from cystic fibrosis patients and normal individuals. The CF cells were found to have 0.73 ± 0.12 fmole/μg protein specifically bound, while normal cells showed 0.25 ± 0.03 fmole/μg protein. Even though this difference is highly statistically significant, we found some overlap between the two cell types from one experiment to another. In any given experiment, however, the CF cells consistently showed increased β-adrenergic binding when compared to normal controls. Binding was measured on plasma membrane extracts from CF and normal fibroblasts. The CF lines continued to show increased specific binding compared to normal lines when partially purified plasma membranes were assayed. The β-adrenergic binding capacity of partially purified plasma membranes was significantly higher (10 times) than the values obtained with whole cells in both cases.