title: Angiotensin II down-regulates the vascular smooth muscle AT1 receptor by transcriptional and post-transcriptional mechanisms: evidence for homologous and heterologous regulation.
abstract: The vascular angiotensin II (ANG II) receptor (AT1) is a central component of the renin-angiotensin system; thus, regulation of its expression is likely to be important in cardiovascular responsiveness. We demonstrate that ANG II down-regulates its receptor in rat aortic vascular smooth muscle cells. Incubation for 4 hr with 100 nM ANG II decreased AT1 mRNA and protein by 70% and 35%, respectively. This homologous down-regulation was concentration and time dependent and was blocked by the AT1 antagonist losartan. It did not appear to be mediated by protein kinase C or other protein kinases but was dependent on the sustained signaling pathway sensitive to phenylarsine oxide. Heterologous down-regulation was observed with the agonists alpha-thrombin and ATP and the cAMP-increasing agent forskolin. ANG II inhibited transcription by 50% and destabilized the AT1 mRNA. Down-regulation of AT1 mRNA was blocked by transcription and translation inhibitors, suggesting that it required expression of a protein factor or factors. These results indicate that ANG II down-regulates its vascular receptor by both transcriptional and post-transcriptional mechanisms. Homologous and heterologous down-regulation of the AT1 receptor may participate in the coordinated physiological adaptation of vascular tone to vasoactive hormones.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000804:Angiotensin II / Q000494:pharmacology*; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D001345:Autoradiography; D001483:Base Sequence; D001713:Biphenyl Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology; D019808:Losartan; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000648:ultrastructure*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D058906:Purinergic P1 Receptor Agonists; D058910:Purinergic P2 Receptor Agonists; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011945:Receptors, Angiotensin / Q000235:genetics / Q000378:metabolism*; D018047:Receptors, Purinergic P1 / Q000502:physiology; D018048:Receptors, Purinergic P2 / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects; D013777:Tetrazoles / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects*
chemical_list: D057911:Angiotensin Receptor Antagonists; D001713:Biphenyl Compounds; D007093:Imidazoles; D009124:Muscle Proteins; D011500:Protein Synthesis Inhibitors; D058906:Purinergic P1 Receptor Agonists; D058910:Purinergic P2 Receptor Agonists; D012333:RNA, Messenger; D011945:Receptors, Angiotensin; D018047:Receptors, Purinergic P1; D018048:Receptors, Purinergic P2; D013777:Tetrazoles; D000804:Angiotensin II; D003609:Dactinomycin; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D011493:Protein Kinase C; D019808:Losartan; D002118:Calcium