P178 Central or Peripheral Injection of a Formulation Containing the Angiotensinergic Dipeptide Asp-Arg Reduces Arterial Pressure and Cardiac Inotropy in Hypertensive Rats

Background and objective: Acute injection of Angiotensin 1-2 Ang-(1-2) reduced arterial pressure and heart rate, and improved coronary perfusion in normotensive and hypertensive rats. Formulations that confer stability and protection against proteolysis are requisites to the feasibility peptides. Next, we evaluated in rats the cardiovascular effects of peripheral or central injections of a complex containing Ang-(1-2) surrounded by a cyclodextrin. Methods: Ethics committee approval by CEUA-FOAr/UNESP 15/2022. We used male Holtzman rats that underwent 2 kidneys, 1 clip (2K1C) hypertension or sham surgery. Six weeks later, rats were separated in different experimental sets (n=4-6 per group) and were instrumented for intracerebroventricular (i.c.v.) and intravenous (i.v.) injections while recording arterial and cardiac left ventricular pressures. The dipeptide was injected i.c.v. (1, 25, 50 and 250pmol/2 μL) or i.v. (25mmol/0.1 mL). Results: dipeptide i.c.v. (25, 50 or 250pmol) reduced arterial pressure of normotensive rats (Δ=-20±3, -20±1 and -18±7mmHg respectively, P<0.05 vs. baseline). In 2K1C, the antihypertensive effect was observed at all doses (Δ=-19±4, -26±5, -19±3 and -17±1mmHg respectively, P<0.05 vs. baseline). I.v. injection of the dipeptide evoked slight increase in arterial pressure (Δ=7±3mmHg; P<0.05 vs. baseline) that was accompanied by a positive inotropic effect (Δ=524±159mmHg/s; P<0.05 vs. baseline). In 2K1C, this same injection reduced arterial and ventricular pressures (Δ=-14±4 and -20±1mmHg respectively, P<0.05 vs. baseline), and caused negative inotropy (ΔLVdP/dtmax=-1140±170mmHg/s; P<0.05 vs. baseline). I.c.v. injection of dipeptide in anesthetized normotensive rats discretely increased arterial and ventricular pressures, while in 2K1C group it reduced arterial and ventricular pressures (Δ=-17±3 and -18±4mmHg respectively, P<0.05 vs. baseline). The ratio between the variations in contractility and mean arterial pressure revealed afterload-independent inotropic effects, i.e, the dipeptide directly affects heart performance of 2K1C. Conclusions: The formulation containing Asp1-Arg2 reduces arterial pressure and modulates cardiac function during hypertension. Whether Ang-(1-2) acts through some antagonism on Angiotensin II receptors or other paths remain to be investigated. Support: CONFAP-FAPESP/FAPEG 2019/24154-3, PROPe-UNESP 13/2022, CNPq-404079/2021-0 and FAPEG-202310267000206.