PAST ISSUES

Recent Update of Renin-angiotensin-aldosterone System in the Pathogenesis of Hypertension

Ju Young Moon

The activation of renin-angiotensin-aldosterine system(RAAS) is one of the main pathogenesis of hypertension. All the components of RAAS are present in the kidneys at higher concentrations compared to plasma levels, and intrarenal formation of angiotensin II (Ang II) is independent of the systemic RAAS. There are some unique features in intrarenal RAAS compared to systemic RAAS. Unlike JG cells where Ang II inhibits renin release via the AngII type 1 (AT1) receptor by negative feedback, in the collecting duct Ang II stimulates renin expression via the AT1 receptor. Upregulated renin produced in the distal nephron may be able to support continued intrarenal Ang II formation leading to amplification or maintenance of the hypertensive state.The recently discovered angiotensin-converting enzyme-related carboxypeptidase 2 (ACE2)-Angiotensin-( 1-7) Ang-(1-7)]-Mas receptor axis has an opposing function to that of the ACE-Ang II-AT1 receptor axis.The ACE2 deficiency was associated with anincrease in blood pressure, and ACE2 knockout mice have highlighted hypertensive response to Ang II infusion associated with exaggerated accumulation of Ang II in the kidney. Recently, several numbers of patients have been evaluated as the activators of ACE2-Ang-(1-7)-Mas receptor axis, which can be divided into two main classes: aimed to increase the activity of ACE2, and directed to stimulate the Ang-(1-7) receptor Mas. In order to investigate new targets for hypertension and kidney disease, further research on the function of the ACE-Ang-(1-7)-Mas receptor axis is required.

  • Electrolytes & Blood Pressure Vol.11:41-45, 5 Pages, 2013

Obesity Associated Hypertension: New Insights into Mechanism

Young Sun Kang

With excess nutrition, the burden of obesity is a growing problem worldwide. The imbalance between energy intake and expenditure leads to variable disorders as all major risk factors for cardiovascular disease. There are many hypothetical mechanisms to explain obesity-associated hypertension. Activation of the RAAS is a key contributing factor in obesity. Particularly, the RAAS in adipose tissue plays a crucial role in adipose tissue dysfunction and obesity-induced inflammation. The phenotypic changes of adipocytes occur into hypertrophy and an inflammatory response in an autocrine and paracrine manner to impair adipocyte function, including insulin signaling pathway. Adipose tissue produce and secretes several molecules such as leptin, resistin, adiponectin, and visfatin, as well as cytokines such as TNF-α, IL-6, MCP-1, and IL-1. These adipokines are stimulated via the intracellular signaling pathways that regulate inflammation of adipose tissue. Inflammation and oxidative stress in adipose tissue are important to interact with the microvascular endothelium in the mechanisms of obesity-associated hypertension. Increased microvascular resistance raises blood pressure. Therefore, a regulatory link between microvascular and perivascular adipose tissue inflammation and adipokine synthesis are provided to explain the mechanism of obesity-associated hypertension.

  • Electrolytes & Blood Pressure Vol.11:46-52, 7 Pages, 2013

Severe Hypernatremia by Excessive Bamboo Salt Ingestion in Healthy Young Woman

Hyun Jun Ju, Hong Jin Bae, Dae Eun Choi, Ki Ryang Na, Kang Wook Lee, Young Tai Shin

Severe hypernatremia is an important electrolyte disorder that has seriouseffects. The patient had no medical history. A. 20-year-old ingested bamboo salt for digestion and weight reduction according to the folk remedies posted on an internet website. She presented with vomiting and diarrhea over ten times per day. Her initial serum sodium concentration was 174mEq/L. Her symptoms improved rapidly with hypotonic saline infusion. She recovered completely without any sequelae in three days. Severe hypernatremia in a normal young adult with clear consciousness and normal renal function has not been reported in Korea yet. So we report a case of severe hypernatremia by excessive bamboo salt inges- tion in healthy young woman.

  • Electrolytes & Blood Pressure Vol.11:53-55, 3 Pages, 2013

Severe Hyponatremia Associated with the Use of Angiotensin II Receptor Blocker/thiazide Combinations

Da Rae Kim, Joo Hee Cho, Won Seok Jang, Jin Sug Kim, Kyung Hwan Jeong, Tae Won Lee, Chun Gyoo Ihm

There are several widely used combinations of angiotensin II receptor blocker (ARB)/ thiazide. The complimentary mechanism of action for such antihypertensive therapies is that, while ARB inhibits the vasoconstricting and aldosterone-secreting effects of angiotensin II, hydrochlorothiazide affects the renal tubular mechanisms of electrolyte reabsorption and increases excretion of sodium and chloride in the distal tubule, consequently promoting water excretion. In addition, hypokalemia, which may be triggered by a hydrochlorothiazide-induced increase in urinary potassium loss, is resisted by the use of ARB. Hence, the ARB/thiazide combination is safe in terms of potassium imbalance. For these reasons, fixed-dose ARB/thiazide combination anti-hypertensive drugs have been widely used for the treatment of hypertension. However, there have not been many studies done regarding cases where patients under such regimens showed severe hyponatremia,even when the amount of thiazide included was low. Here we report two cases in which severe hyponatremia occurred following treatment with the ARB/thiazide combinations. Upon discontinuation of the regimen, both patients showed recovery from hyponatremia.

  • Electrolytes & Blood Pressure Vol.11:56-59, 4 Pages, 2013