Renal responses to angiotensin II infusion in early type 1 (insulin-dependent) diabetes.

The renal response to infusion of sub-pressor doses of angiotension II was examined in nine euglycaemic Type 1 (insulin-dependent) diabetic patients with diabetes of short duration and nine non-diabetic control subjects. Plasma concentrations of angiotensin II and of free insulin were similar in both groups at baseline and during angiotensin II infusion. Glomerular filtration rate (Inutest clearance) fell to a similar extent during angiotensin II infusion in both groups (diabetic 116(SE 5) to 102(5) ml min-1 1.73-m-2; control 113(6) to 100(5) ml min-1 1.73-m-2). There was a large dose-dependent fall in effective renal plasma flow (p-aminohippurate clearance) during angiotensin II infusion which was of similar magnitude in both groups (diabetic; 694(46) to 521(21) ml min-1 1.73-m-2; control 665(41) to 498(30) ml min-1 1.73-m-2). The absolute and the fractional rates of urinary excretion of sodium were both lower in the diabetic group throughout the study, but there was a comparable antinatriuretic response to angiotensin II. Thus, the renal haemodynamic response to angiotensin II infusion is normal in early well-controlled Type 1 diabetes. Differences were found in the renal handling of sodium, which could not be related to altered renal tubular responses to angiotensin II or to peripheral hyperinsulinaemia.     

Inverse variations of plasma renin activity and renin substrate in normal man

Abstract. In the control subject, plasma angiotensin production is a linear function of plasma renin content. Upon incubation of this same plasma in the presence of an excess of homologous renin, angiotensin production is finally limited by the plasma content of renin substrate (PRS). By this method, PRS levels were measured and compared with levels of plasma renin activity (PRA), urinary aldosterone excretion, and sweat sodium and potassium content, in sixteen normal human subjects, aged twenty-five to thirty years, under three defined metabolic conditions: unrestricted sodium intake, salt depletion, constant sodium intake plus administration of desoxycorticosterone acetate (DOCA). 1) Unrestricted Sodium Intake. In these control subjects, in perfect health, there exist important individual differences in PRS levels. The PRS levels seem to be quite constant for a given subject under a given metabolic condition: the levels remained the same after a four month interval for a given subject. 2) Salt Depletion. Activation of the renin-angiotensinaldosterone system (RAAS), as shown by an elevation of PRA and of urinary aldosterone excretion, is accompanied by a decrease in PRS levels. 3) Constant Sodium Intake Plus Administration of DOCA. Inactivation of the RAAS, as shown by lowering of PRA and of urinary aldosterone excretion, is accompanied by a marked elevation of PRS levels. It would appear that, in human control subjects there exists an inverse relationship between PRS and PRA levels.     

Plasma renin activity in essential hypertension

Summary A study of the frequency distribution of plasma renin activity (PRA) in 123 patients with essential hypertension (EH) produced no evidence of a distinct subpopulation with low renin levels, whether the samples were taken from supine or upright patients. Applying an arbitraty classification criterion, however, low PRA levels were found in 30.1% of patients. There were no significant differences in mean blood pressure, 24-h sodium excretion, and age when groups with low, normal or high PRA levels were compared. The incidence of PRA hyporesponsiveness was similar in the three groups of patients, but increased with age. In the female there was a preponderance of low PRA levels. It is concluded that EH with low PRA levels is not a separate diagnostic entity and, when PRA is low in a hypertensive subject, the possible effects of age, blood pressure, and sex ought to be taken into account before other causes of low PRA are postulated.     

The renin angiotensin system and the metabolic syndrome

The renin angiotensin system (RAS; most well-known for its critical roles in the regulation of cardiovascular function and hydromineral balance) has regained the spotlight for its potential roles in various aspects of the metabolic syndrome. It may serve as a causal link among obesity and several co-morbidities. Drugs that reduce the synthesis or action of angiotensin-II (A-II; the primary effector peptide of the RAS) have been used to treat hypertension for decades and, more recently, clinical trials have determined the utility of these pharmacological agents to prevent insulin resistance. Moreover, there is evidence that the RAS contributes to body weight regulation by acting in various tissues. This review summarizes what is known of the actions of the RAS in the brain and throughout the body to influence various metabolic disorders. Special emphasis is given to the role of the RAS in body weight regulation.The paper represents an invited review by a symposium, award winner or keynote speaker at the Society for the Study of Ingestive Behavior [SSIB] Annual Meeting in Portland, July 2009.     

THE EFFECT OF DIFFERENT HYPERTENSION MODELS ON VISUAL EVOKED POTENTIALS

Even though there is an abundance of information about the complications of hypertension, studies of its influence on visual evoked potentials (VEPs) are rare. In previous studies, it was pointed out that hypertension induces changes on VEPs. However, it has not yet been clarified which models of hypertension are more effective on VEPs. The aim of this study was to investigate this subject in rats. Animals were divided equally into six groups: control group (C), sham operated (Sham), two kidney-one clip (2K-1C), one kidney-one clip (lK-lC), deoxycorticosterone-salt (DOCA), and N-omega-nitro-L-arginine-methyl ester (L-NAME) groups. Mean arterial pressure was significantly higher in four hypertensive groups compared with control and sham groups, but there were no significant differences either among hypertensive groups or between sham and control groups. At the end of the experimental period, flash visual evoked potentials were recorded. The mean latencies of P1, N1, P2, N2, and P3 components were significantly prolonged in all hypertensive groups compared with the control and sham groups. The mean latencies of all VEPs components in the L-NAME group were longer than in the other hypertensive groups. Thiobarbituric acid-reactive substances (TBARS) were determined as an indicator of lipid peroxidation. Our data showed that hypertension caused a significant increase of lipid peroxidation in brain and retinal tissues. Additionally, plasma renin activity (PRA) was highest in the 2K-1C group and lowest in the DOCA group.     

血栓抽吸治疗急性ST段抬高型心肌梗死前后神经内分泌因子水平的变化

目的探讨应用血栓抽吸装置GuardWire Plus^TM行血栓抽吸治疗急性sT段抬高型心肌梗死（STEMI）对神经内分泌因子水平、外周血肌钙蛋白（cTnI）、TIMI血流变化的影响及其临床价值。方法将2004年9月至2006年9月在我院行急诊PCI的72例STEMI患者分为两组，抽吸组（TA组，38例）血栓抽吸后支架置入；非抽吸组（NTA组，34例）单纯PCI。于手术当天、术后第1、2、3、5天分别测定外周血中内皮素（ET）、血浆肾素活性（PRA）、醛固酮（ALD）、血管紧张素Ⅱ（AngⅡ）、去甲肾上腺素（NE）、肾上腺素（E）的水平。于术前、术后4h、8h、12h、16h、24h、2d、3d、5d分别测定外周血中cTnI的水平。支架置入后常规行冠状动脉造影，观察心肌血流灌注情况，测定支架置入后两组患者的TIMI血流。比较术后2h心电图ST段回落。术后1周及3个月应用彩色超声心动图测定左室射血分数（LVEF），评价心功能。结果两组病例均成功置入支架，术前两组患者的神经内分泌因子水平均显著升高，两组间差异无统计学意义。浓度-时间曲线显示术后神经内分泌因子水平均迅速下降，TA组较NTA组ET、PRA、AngⅡ、ALD、NE、E等神经内分泌因子水平于术后第1天或第2天下降明显[ET：术前152．37ng／L比153．63ng／L（P：0．858），术后第1天128．11ng／L比147．07ng／L（P=0．037），术后第2天122．22ng／L比139．64ng／L（P=0．040）；PRA：术前2．87μL／（L·h）比2．87μL／（L·h）（P=0．998），术后第1天1．74μL／（L·h）比2．54μL／（L·h）（P=0．036），术后第2天1．70μL／（L·h）比2．29μL／（L·h）（P=0．032）；ALD：术前200．14pmol／L比181．19pmol／L（P=0．508），术第1天156．06pmol／L比172．19pmol／L（P=0．001）；AngⅡ：术前199．11ng／L比。212．32ng／L（P=0．539），术后第1天149．26ng／L比188．37ng／L（P=0．040），术后第2天135．57     

Systolic hypertension in the elderly: addressing an unmet need

Systolic hypertension is a major public health issue in the elderly and is often under-recognized and under-treated. The concept that systolic blood pressure increases with age should be considered a pathophysiologic concept. Aging of the cardiovascular system is accompanied by endothelial dysfunction, activation of the renin-angiotensin system and, consequently, vascular remodeling. This process leads to an increase in large artery stiffness and an increase in arterial wave reflections to the heart. These processes in daily clinical practice translate to an increase in systolic blood pressure, which is associated with increased cardiovascular morbidity and mortality. Evidence-based medicine recommendations to treat systolic hypertension in the elderly are based on landmark and recent clinical trials, which clearly demonstrated that treatment of isolated systolic hypertension is associated with significant decreases in cardiovascular morbidity and mortality. However, treatment of systolic hypertension in older adults remains disappointing because therapeutic goals often are not reached. Therefore, emphasis should be placed on the treatment of systolic hypertension in the elderly, and there is need for more effective, individualized antihypertensive therapy.     

心房颤动患者循环血浆肾素、血管紧张素Ⅱ和醛固酮的变化及临床意义

目的 分析心房颤动患者循环血浆肾素、血管紧张素Ⅱ(AngⅡ)、醛固酮(Ald)的水平变化,并探讨其临床意义。方法入选42例患者,男19例,女23例,年龄37-80(63.02±10.66)岁。按有无心房颤动病史分为三组:窦性心律组(SR组)14例,阵发性心房颤动组(pAF组)15例,慢性心房颤动组(cAF组)13例。应用放射免疫方法测定循环血浆肾素、AngⅡ、Ald浓度。结果cAF组患者平均左心房直径与SR组和pAF、组相比明显增大(分别增大45.3％和31.8％,P<.01),而且cAF组患者循环血浆肾素、AngⅡ、Ald浓度与SR组相比明显升高(分别升高83.3％、61.7％、34.2％,P<0.01-0.02)。三组患者左心房直径与其循环血浆肾素、AngⅡ、Ald浓度变化具有明显的正相关关系(P<0.05-0.01)。结论心房颤动时存在肾素-血管紧张素系统(RAS)和Ald的激活。RAS和Ald可能参与了心房结构重构的发生。Ald的作用靶点可能主要是心房间质。