Abstract
Prolonged agonist stimulation of beta2-adrenoceptors results in receptor
down-regulation which is often paralleled by a reduction of the corresponding
mRNA. In this study, we investigated the agonist-dependent regulation
of beta2-adrenoceptor mRNA in DDT1-MF2 smooth muscle cells and C6
glioma cells. In DDT1-MF2 cells the half-life of the mRNA was 12
h in monolayer compared to 2 h in suspension cultures. Under both
conditions, the agonist isoproterenol reduced this half-life by a
factor of 2. In contrast, in C6 glioma cells isoproterenol had no
effect on the mRNA stability, even though it reduced mRNA levels
by approximately 50%. Isoproterenol-induced downregulation of beta2-adrenoceptor
mRNA was completely blocked in C6 cells by the presence of a protein
synthesis inhibitor, while this was not so in DDT1-MF2-cells. These
data show that beta2-adrenoceptor downregulation occurs via cell-type
specific mechanisms.
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