Expression of renin-angiotensin system genes in brain structures of ISIAH rats with stress-induced arterial hypertension.

We studied the expression of genes encoding angiotensinogen (Agt), renin (Ren), angiotensin-converting enzyme (ACE), and type 1 angiotensin receptor (AT1A) in the hypothalamus and medulla oblongata of hypertensive ISIAH rats and normotensive WAG rats. The amount of Agt mRNA in the hypothalamus of young ISIAH rats was increased by 30% compared to WAG controls. In the medulla oblongata of young ISIAH rats, the levels of mRNA of Agt and AT1A receptor were enhanced by 60% and 24%, respectively, compared to WAG rats. In adult animals, the expression of the studied genes did not differ from the control. It is concluded that changes in gene expression of the renin-angiotensin system in brain structures of ISIAH rats may contribute to the development of hypertension.

Conjugated linoleic acid supplementation enhances antihypertensive effect of ramipril in Chinese patients with obesity-related hypertension.

BACKGROUND: Conjugated linoleic acid (CLA) refers to a group of positional and geometrical conjugated dienoic isomers of linoleic acid. Our aim was to investigate the effect of 8-week dietary CLA supplementation on blood pressure, concentrations of plasma adiponecin, leptin, and as well as angiotensin-converting enzyme (ACE) activity in obese hypertensive subjects. METHODS: Eighty obese individuals with stage 1 uncontrolled essential hypertension were randomized in a double-blind, placebo-controlled trial. Participants were randomized to a daily dose of 4.5 g/day CLA (nine 0.5-g capsules; a 50:50 isomer blend of c 9,t 11 and t 10,c 12 CLA) with 37.5 mg/day ramipril (group 1) or placebo with 37.5 mg/day ramipril (group 2) for 8 weeks. Baseline and endpoint systolic BP, diastolic BP, and concentrations of plasma adiponecin, leptin, angiotensinogen, and ACE activity were measured. RESULTS: Treatment with CLA significantly enhanced the reduction effect of ramipril on systolic BP and diastolic BP (P < 0.05). It also increased plasma adiponectin concentration (P < 0.05) and decreased plasma concentrations of leptin and angiotensinogen (P < 0.05); however, significant change was not observed in ACE activity. CONCLUSIONS: An 8-week long supplementation of CLA enhanced the effect of ramipril on blood pressure reduction in treated obese hypertensive patients. The antihypertensive effect of CLA might be related to the changed secretion of hypertensive adipocytokines in plasma.

Laughter therapy modulates the parameters of renin-angiotensin system in patients with type 2 diabetes.

The effect of laughter therapy on the plasma levels of renin, angiotensinogen, and prorenin was investigated in patients with type 2 diabetes. In the diabetic patients, the mean plasma renin concentrations were 24.6+/-12.1 ng/ml/h in the first observation (at the beginning of laughter therapy), 8.2+/-3.4 ng/ml/h in the second observation (three months after the beginning of laughter therapy) and 7.7+/-1.7 ng/ml/h in the third observation (six months after the beginning of laughter therapy). The mean plasma angiotensinogen concentrations in the 1st, 2nd and 3rd observations were 0.19+/-0.08, 0.47+/-0.12, 0.42+/-0.14 microg/ml, respectively. The mean plasma prorenin concentrations in the 1st, 2nd and 3rd observations during the laughter therapy were 195.1+/-66.2, 193.4+/-88.2 and 170.7+/-52.5 pg/ml, respectively. Plasma renin concentrations were significantly decreased (p<0.05) by the therapy. Subnormal concentrations of plasma angiotensinogen were found in the 1st observation and increased significantly (p<0.05) to the normal range after the therapy. Plasma prorenin concentration only slightly changed during the laughter therapy. Other biochemical parameters remained unchanged during the laughter therapy. These results indicated that a long-term laughter therapy changed the plasma components of renin-angiotensin system in patients with diabetes. Thus, laughter therapy can be used as non-pharmacological treatment for the prevention of diabetic microvascular complications.

Oestrogenic regulation of brain angiotensinogen.

Oestrogens are now recognized as playing a regulatory role on components of the systemic renin-angiotensin system, such as its precursor, angiotensinogen (AGT). In the brain, this role is poorly understood. The aim of this study was to investigate the influence of oestrogens on brain AGT of female rats at different stages of the oestrous cycle, in pregnancy and following ovariectomy with and without hormone replacement. AGT content of different brain regions was also studied in male rats treated with oestrogens. The brain was divided into five regions: cortex, cerebellum, brainstem, midbrain and thalamus/hypothalamus, and AGT was measured by direct radioimmunoassay using a highly specific AGT antibody. Cyclical fluctuations in AGT content were observed in all regions except the cerebellum over the course of the 4-day oestrous cycle, with peak concentrations at estrus and lowest concentrations at metestrus. Following ovariectomy, brain AGT was significantly decreased in the thalamic/hypothalamic region, an effect that was reversed by oestrogen-replacement. In pregnant rats, AGT contents were elevated in the brainstem region. Oestrogen treatment of male rats induced significant increases in AGT concentrations in all areas except the cortex. In summary, these results show that oestradiol has actions on brain AGT that are region-specific and dependent on the particular physiological and reproductive context. Moreover, the changes in AGT concentrations in the oestrous cycle suggest the involvement of other factors besides oestrogen. Finally, this study supports the view that the brain renin-angiotensin system has a broad role in oestrogen-modulated brain functions beyond those specific to the hypothalamic-pituitary-ovarian axis.

The interrelation of renin and iron binding capacity.

When rats are subjected to hypoxia, an increase in serum angiotensinogen concentration occurs which is accompanied by the appearance of serum erythropoietin (EP) during the first 24 h. Subsequent increases in EP reach maximum values 24 to 48 h after increases in packed cell volume (PCV) and serum renin levels. The current experiments were designed to determine if a decrease in iron stores is the stimulus for renin production when rats are rapidly expanding their red cell volume in a hypoxic environment. Young rats fed McCall's low iron diet were paired with rats fed the same diet supplemented with ferric citrate (6 g/kg diet). After two weeks at ambient pressure, they were subjected to hypoxia (0.48 atm) for 1 to 10 days. After 5 days at the reduced pressure, a fraction of the rats on the low iron diet were fed the iron-supplemented diet. At the time of sacrifice, serum was assayed for total iron binding capacity (TIBC) and renin. Rats that were fed the low iron diet showed an increase in TIBC, an increase in serum renin and a positive correlation between serum renin and TIBC. Rats that were fed a normal iron diet under the same conditions had lower TIBC, lower serum renin and no correlation between serum renin and TIBC. When low iron diet rats were supplemented with iron, TIBC and serum renin decreased. These experiments may have a clinical counterpart. The total iron binding capacity, renin and angiotensinogen were measured in the serum of women during the first 19 weeks of pregnancy. Women during early pregnancy showed an increase in TIBC, an increase of renin and angiotensinogen in the serum and a positive correlation between TIBC and renin concentration. It is suggested that the increased concentration of renin in the serum of women during the first 19 weeks of pregnancy and in the serum of rats that are rapidly expanding their red cell volume are related to a decrease in iron stores.