Altered regional blood flow distribution in Mas-deficient mice

BACKGROUND: We have recently shown that the acute infusion of angiotensin-(1-7)[Ang-(1-7)] or chronic increase in plasma Ang-(1-7) produces important changes inregional blood flow in rats. METHODS: To further assess whether these changes arerelated to Mas, in this study hemodynamic measurements were performed inAng-(1-7) receptor Mas knockout C57BL/6 (Mas-KO) mice and age-matched wild type(WT) control mice, using fluorescent microspheres. RESULTS: Mean arterialpressure in urethane-anesthetized Mas-KO mice (12-16 weeks old) did not differfrom that in WT mice (79 +/- 2 and 80 +/- 2 mmHg respectively). However,pronounced differences were observed in other hemodynamic measurements. Mas-KOmice exhibited a significant decrease in stroke volume (0.03 +/- 0.01 versus 0.05+/- 0.01 ml/beat in WT) and decreased cardiac index (0.81 +/- 0.08 versus 1.24+/- 0.24 ml/min/g in WT). Strikingly, Mas-KO mice exhibited a marked increase in vascular resistance and a decrease in blood flow in the kidney, lung, adrenalgland, mesentery, spleen and brown fat tissue. The decrease in blood flow ranged from 34% (spleen) to 55% (brown fat tissue). CONCLUSION: These results suggestthat the Ang-(1-7)/Mas axis plays an important role in regional and systemichemodynamic adjustments in mice