Adenylate cyclase activity was measured in membrane preparations of cultured fibroblasts from controls and patients with cystic fibrosis. Enzyme activity increased as the transition from exponential growth to confluence occurred; sodium fluoride-stim- ulated activity more markedly displayed this relationship than basal cyclase activity. The in vitro addition of spermine (1 × 10-6 to 2 × 10-3 M) to membrane preparations caused inhibition of basal and sodium fluoride-stimulated enzyme activity, with 50% inhibition of basal activity occurring at 10-6 M spermine. Spermidine (10-4 M) caused 15-25% inhibition of adenylate cyclase activity. The increase in fibroblast adenylate cyclase activity during the transition from exponential growth was comparable in cells obtained from cystic fibrosis patients and control subjects. Basal and sodium-fluoride stimulated adenylate cyclase activity as well as inhibition of this enzyme activity by spermidine and spermine were undistinguishable between the different cell genotypes. A potential modulation of cellular proliferative activity through polyamine interaction with the adenylate cyclase system is postulated. Speculation: Buchwald and associates (5) observed increased levels of cyclic AMP in cultured fibroblasts obtained from cystic fibrosis patients. Similarly, Mangos and collaborators (15) have suggested that altered regulation of cyclic nucleotide metabolism may be an etiologic factor in the pathophysiology of the exocrine dysfunction of cystic fibrosis. Effector molecules whose actions are mediated through changes in cyclic nucleotide metabolism induce changes in both the polyamine biosynthetic machinery and in the intracellular concentrations of these amines. These changes in polyamine metabolism occur concomitantly or precede those of cyclic nucleotide metabolism. This investigation postulates that the naturally occurring polyamines putrescine, spermidine and spermine act as second messengers and may exert their effects by modulating adenylate cyclase. Since an abnormality of polyamine metabolism occurs in cystic fibrosis, these relationships of polyamine modulation of adenylate cyclase activity were investigated in cystic fibrosis fibroblasts.
ASJC Scopus subject areas
- Pediatrics, Perinatology, and Child Health