Hypotensive effect induced by microinjection of Alamandine, a derivative of angiotensin-(1–7), into caudal ventrolateral medulla of 2K1C hypertensive rats

Abstract

In the present study we evaluated the cardiovascular effects produced by microinjection of the new component of the renin-angiotensin system, alamandine, into caudal ventrolateral medulla of urethane-anesthetized normotensive and hypertensive 2K1C rats. The participation of different angiotensin receptors in the effects of alamandine was also evaluated. Microinjection of angiotensin-(1–7) was used for comparison. The microinjection of 4, 40 and 140pmol of alamandine or angiotensin-(1–7) into caudal ventrolateral medulla induced similar hypotensive effects in Sham-operated rats. However, contrasting with angiotensin-(1–7), in 2K1C rats the MAP response to the highest dose of alamandine was similar to that observed with saline. The microinjection of A-779, a selective Mas receptor antagonist, blunted the angiotensin-(1–7) effects but did not block the hypotensive effect of alamandine in Sham or in 2K1C rats. However, microinjection of D-Pro7-angiotensin-(1–7), a Mas/MrgD receptor antagonist, blocked the hypotensive effect induced by both peptides. Furthermore, microinjection of PD123319, a putative AT2 receptor antagonist blocked the hypotensive effect of alamandine, but not of angiotensin-(1–7), in Sham and 2K1C rats. Microinjection of the AT1 receptor antagonist, losartan, did not alter the hypotensive effect of angiotensin-(1–7) or alamandine in both groups. These results provide new insights about the differential mechanisms participating in the central cardiovascular effects of alamandine and angiotensin-(1–7) in normotensive and 2K1C hypertensive rats.