Enhanced adenosine 3':5' - monophosphate response to beta-adrenergic stimulation in cystic fibrosis fibroblasts after removal of conditioned medium.

Skin fibroblasts derived from 6 patients with cystic fibrosis (CF), 1-6 months old, and from 6 age matched donors were investigated for their ability to accumulate cyclic adenosine 3':5'-monophosphate (c-AMP) in response to isoproterenol and prostaglandin E1 (PGE1) using strictly defined culture conditions. In order to obtain, as far as possible, constant protein content and cell number, cultures were synchronized in the early G1 phase of the cell cycle by growing them in serum free medium before adding stimulating drugs. There were no statistically significant differences both in basal c-AMP or after incubation with theophylline alone. When cultures were thoroughly washed prior to stimulation, c-AMP accumulation in response to isoproterenol was consistently higher (p less than 0.001) in CF than in normal fibroblasts, whereas response to PGE, did not differ significantly. This difference in response cannot be attributed to differences in dose- or time-response curves, or to differential escape of cAMP into the culture medium. Returning the conditioned media (CM) to the cultures after the washing procedure, or omitting the washing procedure altogether, normalized the cAMP response of CF cells. These data indicate that CF fibroblasts "delete" or "add to" the conditioned medium a substance when washed out of the cultures leave the cells hypersensitized to beta-adrenergic stimulation.