Expression Of ACE2 Protein And MRNA In Kidney In Spontaneously Hypertensive Rats

【Objective】To investigate the expression of angiotensin-converting enzyme 2(ACE2) protein and mRNA in kidney of different age spontaneously hypertensive rats(SHR)and to explore the role of this enzyme in the development of hypertension.【Methods】Male SHR(n=30) were allocated to five groups by age: 1)one-month-old group(S1); 2)two-month-old group(S2); 3)three-month-old group(S3); 4)six-month-old group(S6); 5)nine-month-old group(S9). Sex and age matched Wistar-Kyoto normotensive rats(WKY)served as controls. Blood pressure was measured. Plasma concentration of angiotensinⅡ(AngⅡ)was measured by radioimmunoassay(RIA). The expression of ACE2 mRNA was determined by reverse transcription polymerase chain reaction(RT-PCR). The expression of ACE2 in kidney was examined by immunohistochemistry and computer image analysis.【Results】An age-dependent increase of SBP was observed in SHR before six months(P<0.05), but there was no similar trend in WKY(P>0.05); the SBP was higher in S6 than that in S1(P<0.05), and no difference was observed between S6 and S9(P>0.05); the SBP was higher in the different age SHR than that in the matched WKY(P<0.05).Plasma AngⅡconcentration was higher in S2, S3, S6 and S9 than that in S1(P<0.05), and no difference was observed among S2, S3, S6 and S9(P<0.05); no difference was observed between the different age WKY(P>0.05); plasma AngⅡ concentration was higher in S2, S3, S6 and S9 than that in the matched WKY(P<0.05).The change trend of ACE2 mRNA expression in the kidneys of the different age SHR was similar to that of the matched WKY. An age-dependent increase of the ACE2 mRNA levels was observed in SHR and WKY(P<0.05), which reached the peak in the third month(P<0.05)and remained stable after the sixth month(P>0.05). The ACE2 mRNA levels were lower in SHR than those in the matched WKY(P<0.05).ACE2 immunostaining was localized throughout the cortex and outer medulla, but there was little or no staining in the inner medulla region. And ACE2 immunostaining was visualized in the cytoplasma of the renal tubule cells, but there was no immunostaining within the glomeruli. The quantification of ACE2 immunohistochemical staining showed: the change trend of ACE2 expression was parallel with that of ACE2 mRNA expression. An age-dependent increase of the ACE2 was observed in SHR and WKY(P<0.05), which reached the peak in the third month and remained stable after the sixth month. The ACE2 levels were lower in SHR than those in the matched WKY(P<0.05). Interestingly, the ACE2 stained area was higher in the inner medulla region than that in the cortex and outer medulla in one-month-old SHR and WKY (P<0.05), which was different from the distribution of other groups.【Conclusions】The expression of ACE2 mRNA and protein in kidney of SHR is decreased compared with WKY.The expression of ACE2 mRNA and protein in kidney has space-time difference.