G-protein-coupled receptor MAS deletion produces a preeclampsia-like phenotype in FVB/N mice.

BACKGROUND: An unbalance in the renin-angiotensin (Ang) system (RAS) between the Ang II/AT1 and Ang-(1-7)/Mas axis appears to be involved in preeclampsia (PE), in which a reduction in Ang-(1-7) was observed. Here, we tested whether the reduction in the activity of the Ang-(1-7)/Mas axis could be a contributing factor for the development of PE, using Mas-deficient (Mas-/-) mice. METHODS AND RESULTS: Cardiovascular parameters were evaluated by telemetry before, during pregnancy and 4 days postpartum in 20-week-old Mas-/- and wild-type (WT) female mice. Mas-/- mice presented reduced arterial blood pressure (BP) at baseline (91.3 ± 0.8 in Mas-/- vs. 94.0 ± 0.9 mmHg in WT, Diastolic, P<0.05). However, after the 13th day of gestation, BP in Mas-/- mice started to increase, time-dependently, and at day 19 of pregnancy, these animals presented a higher BP in comparison with WT group (90.5 ± 0.7 in Mas-/- vs. 80.3 ± 3.5 mmHg in WT, Diastolic D19, P<0.0001). Moreover, pregnant Mas-/- mice presented fetal growth restriction, increase in urinary protein excretion as compared with nonpregnant Mas-/-, oliguria, increase in cytokines, endothelial dysfunction and reduced ACE, AT1R, ACE2, ET-1A, and eNOS placental mRNA, similar to some of the clinical manifestations found in the development of PE. CONCLUSIONS: These results show that Mas-deletion produces a PE-like state in FVB/N mice.

Influence of antihypertensive drugs on aortic and coronary effects of Ang-(1-7) in pressure-overloaded rats

This study investigated the influence of antihypertensive drugs, such as angiotensin-converting enzyme inhibitors (ACEIs), AT1 receptor blockers (ARBs), voltage-gated L-type calcium channel blockers, and mineralocorticoid receptor antagonists (MRAs), on the effects of angiotensin-(1-7) [Ang-(1-7)] on aorta and coronary arteries from pressure-overloaded rats. Pressure overload was induced by abdominal aortic banding (AB). To evaluate the role of antihypertensive drugs on the effect of Ang-(1-7), AB male Wistar rats weighing 250–300 g were treated with vehicle or low doses (5 mg·kg-1·day-1, gavage) of losartan, captopril, amlodipine, or spironolactone. Isolated aortic rings and isolated perfused hearts under constant flow were used to evaluate the effect of Ang-(1-7) in thoracic aorta and coronary arteries, respectively. Ang-(1-7) induced a significant relaxation in the aorta of sham animals, but this effect was reduced in the aortas of AB rats. Chronic treatments with losartan, captopril or amlodipine, but not with spironolactone, restored the Ang-(1-7)-induced aorta relaxation in AB rats. The coronary vasodilatation evoked by Ang-(1-7) in sham rats was blunted in hypertrophic rats. Only the treatment with losartan restored the coronary vasodilatory effect of Ang-(1-7) in AB rat hearts. These data support a beneficial vascular effect of an association of Ang-(1-7) and some antihypertensive drugs. Thus, this association may have potential as a new therapeutic strategy for cardiovascular diseases.

Time-course effects of aerobic exercise training on cardiovascular and renal parameters in 2K1C renovascular hypertensive rats

Exercise training (Ex) has been recommended for its beneficial effects in hypertensive states. The present study evaluated the time-course effects of Ex without workload on mean arterial pressure (MAP), reflex bradycardia, cardiac and renal histology, and oxidative stress in two-kidney, one-clip (2K1C) hypertensive rats. Male Fischer rats (10 weeks old; 150–180 g) underwent surgery (2K1C or SHAM) and were subsequently divided into a sedentary (SED) group and Ex group (swimming 1 h/day, 5 days/week for 2, 4, 6, 8, or 10 weeks). Until week 4, Ex decreased MAP, increased reflex bradycardia, prevented concentric hypertrophy, reduced collagen deposition in the myocardium and kidneys, decreased the level of thiobarbituric acid-reactive substances (TBARS) in the left ventricle, and increased the catalase (CAT) activity in the left ventricle and both kidneys. From week 6 to week 10, however, MAP and reflex bradycardia in 2K1C Ex rats became similar to those in 2K1C SED rats. Ex effectively reduced heart rate and prevented collagen deposition in the heart and both kidneys up to week 10, and restored the level of TBARS in the left ventricle and clipped kidney and the CAT activity in both kidneys until week 8. Ex without workload for 10 weeks in 2K1C rats provided distinct beneficial effects. The early effects of Ex on cardiovascular function included reversing MAP and reflex bradycardia. The later effects of Ex included preventing structural alterations in the heart and kidney by decreasing oxidative stress and reducing injuries in these organs during hypertension.

Effects of short-term administration of estradiol on reperfusion arrhythmias in rats of different ages

Little is known about age-related differences in short-term effects of estradiol on ischemia-reperfusion (I/R) insults. The present study was designed to evaluate the effects of short-term treatment with estradiol on reperfusion arrhythmias in isolated hearts of 6-7-week-old and 12-14-month-old female rats. Wistar rats were sham-operated, ovariectomized and treated with vehicle or ovariectomized and treated with 17β-estradiol (E2; 5 µg·100 g-1·day-1) for 4 days. Hearts were perfused by the Langendorff technique. Reperfusion arrhythmias, i.e., ventricular tachycardia and/or ventricular fibrillation, were induced by 15 min of left coronary artery ligation and 30 min of reperfusion. The duration and incidence of I/R arrhythmias were significantly higher in young rats compared to middle-aged rats (arrhythmia severity index: 9.4 ± 1.0 vs 3.0 ± 0.3 arbitrary units, respectively, P < 0.05). In addition, middle-aged rats showed lower heart rate, systolic tension and coronary flow. Four-day E2 treatment caused an increase in uterine weight. Although E2 administration had no significant effect on the duration of I/R arrhythmias in middle-aged rats, it induced a marked reduction in the rhythm disturbances of young rats accompanied by a decrease in heart rate of isolated hearts. Also, this reduction was associated with an increase in QT interval. No significant changes were observed in the QT interval of middle-aged E2-treated rats. These data demonstrate that short-term estradiol treatment protects against I/R arrhythmias in hearts of young female rats. The anti-arrhythmogenic effect of estradiol might be related to a lengthening of the QT interval.