Effect of renin-angiotensin system blockade on the expression of the angiotensinogen gene and induction of hypertrophy in rat kidney proximal tubularcells

Studies have shown that high levels of glucose and angiotensin II (Ang II) stimulate hypertrophy and the expression of matrix protein genes in mouse p roximal tubular cells in vitro. The present study tested the hypothesis tha t blockade of the renin-angiotensin system (RAS) inhibits the stimulatory e ffect of high levels of glucose on the expression of the renal angiotensino gen (ANG) gene and the formation of Ang II and subsequently attenuates the induction of hypertrophy in kidney proximal tubular cells. Immortalized rat proximal tubular cells (IRPTC) were cultured in monolayer. The levels of e xpression of rat ANG and ANG mRNA in the IRPTC were quantified by specific radioimmunoassays for rat ANG (RIA-rANG) and by a reverse-transcription pol ymerase chain reaction (RT-PCR) assay, respectively. Hypertrophy of IRPTC w as analyzed by flow cytometry (FACScan) and cellular protein assay. Our stu dies showed that losartan (an Ang II (AT(1))-receptor blocker), perindopril and captopril (inhibitors of angiotensin-converting enzyme) blocked the st imulatory effect of a high level of glucose (i.e. 25 mM) on the expression of the rat ANG gene and hypertrophy in IRPTC but not by the Ang II (AT(2))- receptor blocker. Our studies indicate that the blockade of RAS is effectiv e in inhibiting the stimulatory effect of hyperglycemia on the expression o f the ANG gene and hypertrophy in IRPTC, supporting the notion that the loc al formation of intrarenal Ang II may play a role in the development of ren al hypertrophy during early diabetes. Copyright (C) 2001 S. Karger AG, Base l.