ANGIOTENSIN-CONVERTING ENZYME-INHIBITOR INCREASES ANGIOTENSIN TYPE 1ARECEPTOR GENE-EXPRESSION IN AORTIC SMOOTH-MUSCLE CELLS OF SPONTANEOUSLY HYPERTENSIVE RATS

To examine the regulation of angiotensin receptors in vascular smooth muscle cells, we studied the effects of antihypertensive drugs on angi otensin type 1A (AT1A) receptor gene expression in aortic smooth muscl e cells (ASMCs) from spontaneously hypertensive rats (SHRs) using both ribonuclease protection assay and reverse-transcription polymerase ch ain reaction. An increase in AT1A receptor gene expression in ASMCs of SHRs was induced by treatment with an angiotensin converting enzyme i nhibitor (enalapril) for 2 weeks and 4 weeks, but not by other types o f antihypertensive drugs such as alpha-blocker (doxazosin), alpha,beta -blocker (arotinolol), Ca antagonist (nicardipine) or vascular smooth muscle relaxant (hydralazine). Since all antihypertensive drugs lowere d the blood pressure of the rats almost equally, our results suggest t hat AT1A receptor gene expression in ASMCs of SHRs may be regulated by the vascular renin-angiotensin system.