Expression of AT_1R and AT_2R in the Kidney of Spontaneously Hypertensive Rats at Different Ages

Objective To investigate the expression of AT_1R and AT_2R in the kidney of spontaneously hypertensive rats(SHR)at different age and to explore the role of these recepters in the development of hypertension.Methods Male SHR(n=30) were allocated to five groups by age:1) one-month-old group(S_1);2) two-month-old group(S_2);3) three-month-old group(S_3);4) six-month-old group(S_6);5) nine-month-old group(S_9).Sex-and age-matched Wistar-Kyoto normotensive rats(WKY)served as controls.The blood pressure was measured.The expression of AT_1R and AT_2R in the kidney was examined by immunohistochemistry and computer image analysis.Plasma concentration of angiotensin Ⅱ(Ang Ⅱ)was measured by radioimmunoassay.Results 1.An age-dependent increase of SBP was observed in SHR before six months(P0.05),the SBP remained stable after the sixth month(P0.05). 2.Plasma Ang Ⅱ concentration was higher in S_2,S_3,S_6 and S_9 groups than that in S_1 group(P0.05),and no siginificant difference was observed among S_2,S_3,S_6 and S_9 groups(P0.05).No significant difference was observed between the differently aged WKY rats(P0.05).The plasma Ang Ⅱ concentration was higher in S_2,S_3,S_6 and S_9 groups than that in the matched WKY rats(P0.05).3.An age-dependent increase of the AT_1R was observed in the SHR kidney(P0.05),The AT_1R was higher in SHR than those in the matched WKY rats(P0.05).No significant difference was observed between differently aged WKY rats(P0.05).An age-dependent decrease of AT_2R was observed in the SHR kidneys(P0.05),which was lower in S_6 rats than that in S_1 rats(P0.05),and no significant difference was observed between S_6 and S_9 groups(P0.05).The AT_2R expression was lower in SHR than that in the matched WKY rats (P0.05).Conclusions The expression of AT_1R in the kidney of SHR is increased in comparison with that of WKY rats.The expression of AT_2R in the kidney of SHR is decreased compared with that in WKY rats.An age-dependent variation of AT_1R and AT_2R expression is observed in SHR at different ages.