Exposure of cells to epinephrine for 24 hr induced an unexpected increase in [3H]prazosin binding to intact cells in a clone (H99) of CHO cells stably transfected to express high levels of the hamster alpha-IB adrenergic receptor. Exposure to 10 nM epinephrine for 24 hr increased both the Bmax and KD, values in saturation assays by approximately 2-fold. Upregulation occurred steadily over the 24 hr period, and halfmaximal up-regulation required only 1 nM epinephrine. Upregulation was neither mimicked by phorbol myristate acetate nor inhibited by GF109203X, suggesting that protein kinase C activation is not involved. Up-regulation was markedly inhibited by cycloheximide, suggesting that new protein synthesis is involved. Up-regulation is not simply an artefact of the high level of receptor expression, since up-regulation was also observed in a clone (L3) expressing receptors at lower levels. However, down-regulation was observed in another high-expressing clone (H88) from the same transfection. The molecular basis for these unexpected changes in receptor expression are being further investigated.
|Original language||English (US)|
|State||Published - 1996|
ASJC Scopus subject areas
- Molecular Biology