Different expression of renin-angiotensin system components in hearts of normotensive and hypertensive rats

Tissue renin-angiotensin systems are known to behave differently from the c irculating renin-angiotensin system (RAS). It has already been proposed tha t not only the circulating RAS, but also RAS localized in the cardiac tissu e plays an important role in the heart failure. The objective of this study was to compare the gene expression of individual components of the renin-a ngiotensin system in hearts of normotensive and hypertensive rats. Two gene tically hypertensive rat strains - spontaneously hypertensive rats (SHR) an d hereditary hypertriglyceridemic rats (HTG) - were compared with Wistar-Ky oto (WKY) and Lewis (LEW) normotensive controls. In addition, developmental changes in gene expression of individual components of cardiac RAS were st udied in 20-day-old fetuses, 2-day-old newborns and 3-month-old HTG and LEW rats. In our study, the angiotensinogen gene expression did not differ eit her among adult normotensive and hypertensive strains, or during developmen t. In contrast, the renin gene expression was significantly increased in he arts of hypertensive compared to normotensive rats. Moreover, a 5-fold incr ease of renin mRNA was observed in hearts of HTG rats between day 2 and the third month of age. There was also an age-dependent increase of ACE gene e xpression in both HTG and LEW rats which was substantially delayed in HTG h earts. In conclusion, the results of our study suggest that overexpression of the cardiac renin gene in hypertensive strains could participate in the structural and functional changes of the heart during the development of hy pertension.