Effect of Angiotensin 1-7 on Myocardial Calcium Pump in Salt-Sensitive Hypertensive Rats

Objective — To investigate the effects of angiotensin 1-7 (Ang1-7) on plasma membrane ATPase isoform 1 (PMCA1) in salt-sensitive hypertensive rats. Methods — Thirty newborn male Wistar rats were selected to establish the salt-sensitive hypertensive rat model with sensory nerve injury, which were then randomly divided into 5 groups (n=5), including model group, Telmisartan group, Ramipril group, Ang1-7 group, and A-779 group. Another normal control group was established (n=5). After 4 weeks of intervention, the tail blood pressure of rats in each group was measured, and then the apical tissue of left ventricle was cut. The contents of AngⅡ and Ang1-7 in cardiomyocytes were detected by enzyme-linked immunosorbent assay. The expression of PMCA1 mRNA and protein in heart of salt-sensitive hypertensive rats were detected by RT-PCR and immunohistochemistry. Results — (1) Compared with the normal control group, the concentration of AngⅡ in the myocardium of salt-sensitive hypertensive rats increased (P < 0.05), which decreased after the intervention of Telmisartan and Ramipril (P < 0.05), and no change occurred after the intervention of Ang1-7 in concentration (P＞0.05). (2) Compared with the normal control group, the concentration of myocardial Ang1-7 in salt-sensitive hypertensive rats decreased (P < 0.05), and increased after the intervention of telmisartan and ramipril (P < 0.05), and increased after the intervention of A-779 (P < 0.05). (3) The expression of PMCA1 mRNA and protein in salt-sensitive hypertensive rats was increased compared with the normal control group (P < 0.05), and the expression of Ang-(1-7), telmisartan and ramipril was decreased compared with the model group (P < 0.05). The expression of p38MAPK mRNA and p-p38MAPK protein in the myocardium of salt-sensitive hypertensive rats was increased compared with that in the normal control group (P < 0.05), and the expression of Ang-(1-7), Telmisartan and Ramipril was decreased compared with that in the model group (P < 0.05). Conclusion — Ang-(1-7) may be involved in the regulation of cardiac calcium pump, inhibiting its overcompensation and delaying the occurrence of calcium pump inhibition in the early stage of salt-sensitive hypertension. Ang-(1-7) can inhibit the activity of p38MAPK and protect the heart, and its regulation on PMCA1 may be mediated by the expression of p38MAPK pathway.