摘要
HEK293 cells stably expressing hamster α 1B adrenergic receptor （α 1B AR） were used to observe the effect of norepinephrine （NE） on α 1B AR gene expression. Radioligand binding assays and RNase protection assays were used to determine α 1B AR number and the mRNA level, respectively. Exposure （2\24 h） of HEK293 cells to NE （10 μmol） caused a decrease in α 1B AR mRNA with maximum change found at the 4th hour, and in α 1B AR density at the 24th hour. NE induced decrease in α 1B AR mRNA was inhibited by protein kinase C （PKC） inhibitor calphostin C （0 1 μmol） and mimicked by PKC activator PMA （1 μmol）. Nuclear run off transcription assay showed that treatment of the cells with NE （10 μmol） exerted no effect on the transcription rate of α 1B AR. After the synthesis of new RNAs was inhibited by actinomycin D, NE could not accelerate the degradation of α 1B AR mRNA. The results suggested that in the HEK293 cells NE could induce the down regulation of α 1B AR, and the effects were mediated by PKC pathway. NE could not alter the transcription rate of α 1B AR mRNA, but it might induce the synthesis of some factors and indirectly accelerate the degradation.
HEK293 cells stably expressing hamster α 1B adrenergic receptor (α 1B AR) were used to observe the effect of norepinephrine (NE) on α 1B AR gene expression. Radioligand binding assays and RNase protection assays were used to determine α 1B AR number and the mRNA level, respectively. Exposure (2\_24 h) of HEK293 cells to NE (10 μmol) caused a decrease in α 1B AR mRNA with maximum change found at the 4th hour, and in α 1B AR density at the 24th hour. NE induced decrease in α 1B AR mRNA was inhibited by protein kinase C (PKC) inhibitor calphostin C (0 1 μmol) and mimicked by PKC activator PMA (1 μmol). Nuclear run off transcription assay showed that treatment of the cells with NE (10 μmol) exerted no effect on the transcription rate of α 1B AR. After the synthesis of new RNAs was inhibited by actinomycin D, NE could not accelerate the degradation of α 1B AR mRNA. The results suggested that in the HEK293 cells NE could induce the down regulation of α 1B AR, and the effects were mediated by PKC pathway. NE could not alter the transcription rate of α 1B AR mRNA, but it might induce the synthesis of some factors and indirectly accelerate the degradation.
基金
ProjectsupportedbytheNationalNaturalScienceFoundationofChina(GrantNo .394 70 2 6 8)andtheChinaMedicineBoardofNewYorkInc .
