Tracheal epithelial cells obtained from adult and infant ferrets were grown in primary culture in vitro. Cells from adult animals grew readily, and many ciliated cells were observed in the cultures. Successful cultures were derived from infant animals, but cell number in infant and adult cultures began to decrease after 6 d. Receptor-mediated activation of adenylate cyclase was determined by incubating monolayers of adult or neonatal cells with β-adrenergic agonists, prostaglandin E2 (PGE2) and vasoactive intestinal peptide and measuring cAMP production. /S-adrenergic agonists and PGE2, but not vasoactive intestinal peptide, stimulated production of cAMP in both cell types. The 50% effective concentration for isoproterenol and PGE2 in neonatal ferret tracheal epithelial (NFTE) cells was nearly 10-fold more than for adult ferret tracheal epithelial (FTE) cells, but maximal agonist-stimulated cAMP production was significantly different between the cell types only for PGE2. Radioligand binding studies were performed using the /3-adrenergic antagonist [I25I]iodocya-nopindolol on membrane particulates from confluent monolayers and freshly isolated FTE cells. Binding of iodocya-nopindolol was saturable, stereoselective, and of high affinity (binding affinity = 26.1 ± 6.6 pmol/L, adult; 16.5 ± 5.7 pmol/L, NFTE). Competition studies with the specific β2-adrenergic receptor antagonist, ICI 118 551 revealed a predominance of β2-adrenergic receptors on both adult FTE and NFTE cells. Receptor density was significantly higher in adult FTE compared with NFTE cells (48.2 ± 9.1,18.1 ±1.5 fmol/mg, respectively). Basal adenylate cyclase activity was significantly lower in neonatal cells. Functionally coupled receptors for β-adrenergic agents and PGE2 are present on adult and infant airway epithelium in the ferret. Both the decreased β-adrenergic receptor number and lower adenylate cyclase activity contribute to the blunted cAMP response of NFTE cells.
ASJC Scopus subject areas
- Pediatrics, Perinatology, and Child Health