INDUCTION OF RENIN IN MEDIAL SMOOTH-MUSCLE CELLS BY BALLOON INJURY

We studied the expression of each component of the renin-angiotensin s ystem (renin, angiotensin I-converting enzyme, angiotensinogen, and an giotensin II type I receptor) in balloon-injured rat carotid artery. W e assessed the expression levels of the respective mRNAs by competitiv e polymerase chain reaction. Renin mRNA concentration was markedly inc reased 24 hours after balloon injury and remained higher than that in the control at 7 days after balloon injury. Angiotensin-converting enz yme mRNA concentration was decreased 24 hours after balloon injury and was increased at 14 days after balloon injury. No significant change in angiotensinogen mRNA concentration was observed throughout the stud y period. Angiotensin type I receptor mRNA concentration was increased beginning 3 days after balloon injury and remained higher than that i n the control at 14 days after balloon injury. Immunohistochemical ana lysis showed that renin was transiently expressed in medial smooth mus cle cells after balloon injury. Administration of quinapril markedly r educed neointimal formation and was accompanied by an attenuation of t he increase in the concentrations of angiotensin type I receptor and a ngiotensin-converting enzyme mRNAs. The upregulation of renin mRNA in balloon-injured rat carotid artery preceded and may play a role in neo intimal formation.