Efficacy of Telemedicine in Hypertension Care Through Home Blood Pressure Monitoring and Videoconferencing: Randomized Controlled Trial.

BACKGROUND: The burden of time is often the primary reason why patients discontinue their treatment. Telemedicine may help patients adhere to treatment by offering convenience. OBJECTIVE: This study examined the efficacy and safety of telemedicine for the management of hypertension in Japan. METHODS: Patients with uncomplicated hypertension were recruited through web advertising between November 2015 and February 2017. They were then screened, stratified by office systolic blood pressure (SBP), and randomized into two groups: usual care (UC) and telemedicine. The telemedicine group used a 3G network-attached home blood pressure (BP) monitoring device, consulted hypertension specialists from an academic hospital through web-based video visits, and received prescription medication by mail for 1 year. The UC group used the same BP monitoring device but was managed using self-recorded BP readings, which included their diary entries and office BP taken in a community practice setting. RESULTS: Initial screening was completed by 99 patients, 54% of whom had untreated hypertension. Baseline BP was similar between the groups, but the weekly average SBP at the end of the 1-year study period was significantly lower in the telemedicine group (125, SD 9 mmHg vs 131, SD 12 mmHg, respectively; P=.02). SBP in the telemedicine group was 3.4 mmHg lower in the morning and 5.8 mmHg lower in the evening. The rate of SBP control (135 mmHg) was better in the telemedicine group (85.3% vs 70.0%; P=.01), and significant adverse events were not observed. CONCLUSIONS: We present evidence suggesting that antihypertensive therapy via home BP telemonitoring and web-based video visits achieve better BP control than conventional care and is a safe treatment alternative that warrants further investigation. TRIAL REGISTRATION: UMIN-CTR UMIN000025372; https://tinyurl.com/47ejkn4b.

The current state and future of internet technology-based hypertension management in Japan.

Internet-based information and communication technology is altering our lives. Although medicine is traditionally conservative, it can benefit in many ways from adopting new technology and styles of care. Hypertension is a prime condition for the practical application of digital health management because it is prevalent and undercontrolled, and its primary index, home blood pressure, can be effectively telemonitored. Compared to other conditions that require laboratory measures or the use of drugs with frequent side effects, hypertension can be managed without actual office visits with sufficiently low risk. In this review of hypertension in Japan, we discuss the current and somewhat fragmented state of internet technology and the components and processes necessary for smooth, integrated, and multidisciplinary care in the future. Although further clinical trials are required to show the safety and efficacy of information and communication technology-based care for hypertension, the deployment of telemonitoring and telemedicine in daily practice should be expedited to solve the hypertension paradox. Challenges remain relating to cost, data integration, the redesigning of team-based care, and the improvement of user experience, but information and communication technology-based hypertension management is sure to become pivotal in improving public health.

Cosyntropin stimulation in adrenal vein sampling improves the judgment of successful adrenal vein catheterization and outcome prediction for primary aldosteronism.

The importance of cosyntropin stimulation during adrenal vein sampling (AVS) is not fully established, partly due to insufficient AVS data relating the presence and absence of cosyntropin stimulation with postoperative outcome. Therefore, we investigated differences in AVS indices before and after cosyntropin stimulation, and determined whether unstimulated or stimulated AVS indices better correlated with treatment outcome. A retrospective study was conducted in two parts: one with 185 patients who underwent AVS and the other with 81 patients who underwent unilateral adrenalectomy for unilateral aldosterone oversecretion. The selectivity index (SI), lateralized ratio (LR), and contralateral ratio (CR) before and after cosyntropin stimulations were determined, along with blood pressure outcome 1 year after surgery. Primary aldosteronism was diagnosed according to the Japanese Endocrine Society 2009 guidelines. The percentage of AVS patients with successful catheterization, defined as unstimulated SI > 2 before and stimulated SI > 5, increased after cosyntropin stimulation from 52% to 93% and from 74% to 98% for the right and left adrenal veins, respectively. LR decreased after cosyntropin stimulation (P < 0.001). In the postoperative patients, complete and partial clinical success was achieved in 49 and 27%, respectively. Low CR (<1) and high LR (≥2.6) after cosyntropin stimulation better correlated with postoperative blood pressure outcome than those before stimulation (CR < 1 and LR ≥ 2). These data suggest that cosyntropin stimulation facilitated the judgment of catheter insertion and postcosyntropin AVS indices may be more useful for predicting treatment outcome after unilateral adrenalectomy. Further study should examine the usefulness of cosyntropin stimulation in AVS performed in other settings.

Soluble (pro)renin receptor increased by hypoxia maintains oxidative metabolism in trophoblasts.

Elevated soluble (pro)renin receptor (s(P)RR) concentration in maternal blood is associated with gestational hypertension and preeclampsia. Placenta has abundant expression of (P)RR, and the binding of (P)RR with pyruvate dehydrogenase E1 beta subunit (PDHB) is reported to maintain oxidative metabolism. Thus, we hypothesized that placental hypoxia may increase (P)RR, and the increased (P)RR may preserve PDHB expression. Expression and functional analyses were performed using human placental trophoblast cells, mainly JAR cells. (P)RR co-immunoprecipitated and showed co-immunofluorescence with PDHB mainly in the mitochondria. Hypoxia treatment significantly increased intracellular s(P)RR protein expression, but secreted s(P)RR in the culture medium was decreased by hypoxia. Hypoxia treatment did not alter PDHB expression or activity in the basal condition, but when (P)RR was knocked down by siRNA, PDHB protein and activity were reduced by hypoxia. Acetyl-CoA, the product of PDH activity, was significantly reduced by hypoxia treatment with (P)RR siRNA. S(P)RR is generated from full-length PRR when cleaved by specific proteases. Protease inhibitor experiments suggested furin and site 1 protease as the enzymes generating s(P)RR in JAR cells, and only when treated by site 1 protease inhibitor, PF429242, PDHB protein showed a significant trend to decrease with hypoxia. In JAR cells, hypoxia increased intracellular s(P)RR, and (P)RR preserved the expression and function of PDHB during hypoxia. (P)RR may help maintain oxidative metabolism and efficient energy production during placental ischemia in hypertensive disorders of pregnancy.

Primary aldosteronism in Klinefelter's syndrome: two cases.

SUMMARY: Primary aldosteronism (PA) is more common than expected. Aberrant adrenal expression of luteinizing hormone (LH) receptor in patients with PA has been reported; however, its physiological role on the development of PA is still unknown. Herein, we report two unique cases of PA in patients with untreated Klinefelter's syndrome, characterized as increased serum LH, suggesting a possible contribution of the syndrome to PA development. Case 1 was a 39-year-old man with obesity and hypertension since his 20s. His plasma aldosterone concentration (PAC) and renin activity (PRA) were 220 pg/mL and 0.4 ng/mL/h, respectively. He was diagnosed as having bilateral PA by confirmatory tests and adrenal venous sampling (AVS). Klinefelter's syndrome was suspected as he showed gynecomastia and small testes, and it was confirmed on the basis of a low serum total testosterone level (57.3 ng/dL), high serum LH level (50.9 mIU/mL), and chromosome analysis. Case 2 was a 28-year-old man who had untreated Klinefelter's syndrome diagnosed in his childhood and a 2-year history of hypertension and hypokalemia. PAC and PRA were 247 pg/mL and 0.3 ng/mL/h, respectively. He was diagnosed as having a 10 mm-sized aldosterone-producing adenoma (APA) by AVS. In the APA, immunohistochemical analysis showed co-expression of LH receptor and CYP11B2. Our cases of untreated Klinefelter's syndrome complicated with PA suggest that increased serum LH levels and adipose tissues, caused by primary hypogonadism, could contribute to PA development. The possible complication of PA in hypertensive patients with Klinefelter's syndrome should be carefully considered. LEARNING POINTS: The pathogenesis of primary aldosteronism is still unclear. Expression of luteinizing hormone receptor has been reported in aldosterone-producing adenoma. Serum luteinizing hormone, which is increased in patients with Klinefelter's syndrome, might contribute to the development of primary aldosteronism.

ACTH-Dependent Cyclic Cushing Syndrome Triggered by Glucocorticoid Excess Through a Positive-Feedback Mechanism.

CONTEXT: Cyclic Cushing syndrome is a rare variant of Cushing syndrome that demonstrates periodic cortisol excess. It has been thought that inhibition of a glucocorticoid positive-feedback loop is associated with remission of hypercortisolism in ACTH-dependent cyclic Cushing syndrome. However, the underlying mechanism that triggers the development of the hypercortisolism is still unknown. We observed a case of ACTH-dependent cyclic Cushing syndrome that was developed by exogenous glucocorticoids, possibly through a glucocorticoid positive-feedback loop. CASE DESCRIPTION: A 75-year-old woman had experienced cyclic ACTH and cortisol elevations six times in the previous 4 years. Her diagnosis was cyclic Cushing syndrome. During the hypercortisolemic phase, neither low-dose nor high-dose dexamethasone suppressed her plasma ACTH and cortisol levels. Daily metyrapone therapy decreased her plasma cortisol and ACTH levels during every hypercortisolemic phase. After the sixth remission of a hypercortisolemic phase, she took 25 mg of hydrocortisone for 4 weeks and developed ACTH-dependent hypercortisolemia. Treatment with 1 mg of dexamethasone gradually increased both plasma ACTH and cortisol levels over 2 weeks, resulting in the eighth hypercortisolemic phase. Treatment using a combination of dexamethasone and metyrapone did not increase plasma ACTH or cortisol level and successfully prevented development of ACTH-dependent hypercortisolism. CONCLUSION: We present an interesting case of cyclic Cushing syndrome in which ACTH-dependent hypercortisolemic phases relapsed during exogenous glucocorticoid treatment. A glucocorticoid positive-feedback loop and endogenous glucocorticoid synthesis may play key roles in the periodicity of hypercortisolism in cyclic Cushing syndrome.

Fatal Fournier's gangrene caused by Clostridium ramosum in a patient with central diabetes insipidus and insulin-dependent diabetes mellitus: a case report.

BACKGROUND: Clostridium ramosum is a generally non-pathogenic enteric anaerobe, and Fournier's gangrene is a rare necrotizing soft tissue infection with male predisposition affecting the perineum and the genital area. We report, to our knowledge, the first case of Fournier's gangrene caused by C. ramosum in a female patient with multiple underlying conditions. CASE PRESENTATION: A 44-year-old woman with a 6-year history of insulin-dependent diabetes mellitus after total pancreatectomy and an 11-year history of central diabetes insipidus developed a pain in the genital area after a month of urinary catheter use. The lower abdominal pain worsened gradually over 2 weeks, and the pain, general fatigue, and loss of appetite prompted the patient's hospital admission. As she had severe edema in her pelvic and bilateral femoral areas, ceftriaxone was started empirically after collecting two sets of blood cultures. On hospital day 2, CT examination revealed the presence of necrotizing faciitis in the genital and pelvic areas, and the antibiotics were changed to a combination of meropenem, vancomycin, and clindamycin. Gram-positive cocci and gram-positive rods were isolated from blood cultures, which were finally identified as Streptococcus constellatus and C. ramosum using superoxide dismutase and 16S rDNA sequencing. An emergent surgery was performed on hospital day 2 to remove the affected tissue. Despite undergoing debridement and receiving combined antimicrobial chemotherapies, the patient's clinical improvement remained limited. The patient's condition continued to deteriorate, and she eventually died on hospital day 8. In the present case, the underlying diabetes mellitus, urinary incontinence due to central diabetes insipidus, undernutrition, and edema served as the predisposing conditions. CONCLUSIONS: C. ramosum is a potentially opportunistic pathogen among immunosuppressed persons and a rare cause of necrotizing fasciitis.

Prediction of response to medical therapy by serum soluble (pro)renin receptor levels in Graves' disease.

Antithyroid drugs are generally selected as the first-line treatment for Graves' Disease (GD); however, the existence of patients showing resistance or severe side effects to these drugs is an important issue to be solved. The (pro)renin receptor [(P)RR] is a multi-functional protein that activates the tissue renin-angiotensin system and is an essential constituent of vacuolar H+-ATPase, necessary for the autophagy-lysosome pathway. (P)RR is cleaved to soluble (s)(P)RR, which reflects the status of (P)RR expression. In this retrospective study, we aimed to investigate whether serum s(P)RR concentration can be used as a biomarker to predict the outcome of antithyroid drug treatment in GD patients. Serum s(P)RR levels were measured in 54 untreated GD patients and 47 control participants. Effects of medical treatment with antithyroid drugs on these levels were investigated in GD patients. Serum s(P)RR levels were significantly higher in patients with Graves' disease than in control subjects (P<0.005) and were significantly reduced after medical treatment for Graves' disease. High serum s(P)RR levels were associated with resistance to antithyroid drug treatment, suggesting that serum s(P)RR concentration can be used as a useful biomarker to predict the outcome of antithyroid drug treatment in these patients. Patients with Graves' disease with low body mass index showed higher levels of serum soluble (pro)renin receptor levels than those with high body mass index. In addition, in patients with Graves' disease, serum triglyceride levels were negatively correlated with serum soluble (pro)renin receptor levels. All these data indicated an association between low nutrient condition due to hyperthyroidism and increased (pro)renin receptor expression in these patients, suggesting that (pro)renin receptor expression could be increased in the process of stimulating intracellular energy production via activating autophagy function to compensate energy loss.

Greater reductions in plasma aldosterone with aliskiren in hypertensive patients with higher soluble (Pro)renin receptor level.

The (pro)renin receptor is important in the regulation of the tissue renin-angiotensin-aldosterone system. The benefits and safety of single-aliskiren treatment without other renin-angiotensin-aldosterone system inhibitors remain unclear. The serum level of the soluble form of the (pro)renin receptor is thought to be a biomarker reflecting the activity of the tissue renin-angiotensin-aldosterone system. We investigated the effects of single renin-angiotensin-aldosterone system blockade with aliskiren on renal and vascular functions and determined if serum level of the soluble (pro)renin receptor was a predictor of aliskiren efficacy in hypertensive patients with chronic kidney disease. Thirty-nine essential hypertensive patients with chronic kidney disease in our outpatient clinic were randomly assigned to receive either aliskiren or amlodipine. The parameters associated with renal and vascular functions and indices of renin-angiotensin-aldosterone system components, including serum levels of the soluble form, were evaluated before and after 12-week and 24-week treatment. Blood pressure was not significantly different between the groups. No significant changes in serum levels were observed in the soluble (pro)renin receptor in either group. Urinary albumin, protein excretion, and cardio-ankle vascular index significantly decreased in the aliskiren group. In the aliskiren group, there was a significant negative correlation between the basal level of the soluble (pro)renin receptor and the change in plasma aldosterone concentration. Single renin-angiotensin-aldosterone system blockade with aliskiren showed renal and vascular protective effects independent of blood pressure reduction. Serum levels of the soluble (pro)renin receptor may indicate aldosterone production via the (pro)renin receptor in the adrenal gland.

The rationale and design of reduction of uncontrolled hypertension by Remote Monitoring and Telemedicine (REMOTE) study.

PURPOSE: Although self-measurement of home blood pressure (HBP) is common in Japan and HBP telemonitoring via the Internet is possible, whether telemonitoring improves HBP control better than conventional practice remains unclear. Furthermore, hypertension care with online communication using telemonitored HBP is feasible, whereas the efficacy and safety of such telemedicine have not been established. We aim to compare traditional care, care with office visits using HBP telemonitoring, and antihypertensive telemedicine based on HBP telemonitoring. METHODS AND DESIGN: In total, 444 patients with uncontrolled hypertension will be recruited and randomly assigned to three groups: (1) control: usual care with office visits and HBP self-report, (2) telemonitoring: weekly assessment of transmitted HBP by physicians and treatment adjustment upon office visits, or (3) telemedicine: online communication instead of office visits to adjust medication using telemonitored HBP. Primary outcome is the time to control of HBP, and secondary outcomes include achieved HBP levels, adherence, treatment intensity, adverse events, patient satisfaction and cost-effectiveness. DISCUSSION: Hypertension care with telemonitoring and telemedicine are expected to require shorter time to achieve HBP control compared to usual care. Combining HBP telemonitoring with telemedicine may lower the hurdles for starting and persisting to hypertension treatment and eventually reduce cardiovascular events.

Complete remission of hypertension in a hemodialysis patient after adrenalectomy for primary aldosteronism and renal transplantation.

A 64-year-old man was admitted to our hospital for the hormonal evaluation of a right adrenal adenoma. He had been diagnosed with severe proteinuria and hypertension, and antihypertensive treatment was started at the age of 60. His renal function gradually declined, and hemodialysis was begun at the age of 64. Since his blood pressure was uncontrollable and resistant to antihypertensive treatment, an endocrinological examination was performed for an incidental right adrenal mass detected by computed tomography. The results of screening, including captopril challenge and an adrenocorticotropin stimulation test for primary aldosteronism, and adrenal venous sampling suggested excessive aldosterone secretion from the right adrenal gland. Adrenalectomy was performed; his blood pressure decreased and became well-controlled with a reduced antihypertensive regimen. Furthermore, he received renal transplantation which resulted in normalization of his serum potassium level, improvement of renal function and hormonal levels such as plasma renin activity and aldosterone concentration, and satisfactory blood pressure without any antihypertensive medications. This case is extremely important to demonstrate the effects of adrenalectomy for primary aldosteronism in a hemodialysis patient. It is possible that adrenalectomy may be a useful treatment for primary aldosteronism even in patients undergoing hemodialysis. Careful long-term follow-up of our case and investigations of the efficacy of adrenalectomy in similar cases are needed to address this issue.

Body mass index and contralateral ratio predict outcome following unilateral adrenalectomy in primary aldosteronism.

The effect of unilateral adrenalectomy on blood pressure (BP) outcome in primary aldosteronism (PA) is diverse. Therefore, we sought to investigate the preoperative factors contributing to postoperative BP outcome. Data for 96 PA patients who underwent unilateral adrenalectomy at our institution from January 2000 to February 2015 were retrospectively collected. Based on postoperative BP after a 12-month follow-up period, the patients were categorized into two groups: cured (C) (<140/90 mm Hg with no antihypertensive drug) and not cured (NC) (if not normotensive). Patient demographics, blood and urine data, data of loading tests and adrenal vein sampling were evaluated. In all, 46 patients were categorized as C and 50 patients as NC. There were significantly more males in the NC group. Age, body mass index (BMI), number of antihypertensive drugs prescribed, serum uric acid concentration and contralateral ratio (CR) after adrenocorticotropic hormone stimulation were significantly higher in the NC group. In the multivariate model, BMI and CR significantly correlated with resolution outcome. The optimal cutoff values were 23.3 kg m-2 for BMI and 0.5 for CR, and when both parameters were used as predictors, the most optimal cutoff values for BMI and CR were 25.2 kg m-2 and 0.1, respectively. BMI and CR significantly correlated with BP outcome after adrenalectomy. To our knowledge, this is the first report to show that in addition to BMI, CR is a factor in postoperative BP outcome and to determine the optimal cutoff values of BMI and CR and calculate their sensitivities and specificities.

Urinary Sodium-to-Potassium Ratio Tracks the Changes in Salt Intake during an Experimental Feeding Study Using Standardized Low-Salt and High-Salt Meals among Healthy Japanese Volunteers.

The Na/K ratio is considered to be a useful index, the monitoring of which allows an effective Na reduction and K increase, because practical methods (self-monitoring devices and reliable individual estimates from spot urine) are available for assessing these levels in individuals. An intervention trial for lowering the Na/K ratio has demonstrated that a reduction of the Na/K ratio mainly involved Na reduction, with only a small change in K. The present study aimed to clarify the relationship between dietary Na intake and the urinary Na/K molar ratio, using standardized low- and high-salt diets, with an equal dietary K intake, to determine the corresponding Na/K ratio. Fourteen healthy young adult volunteers ingested low-salt (3 g salt per day) and high-salt (20 g salt per day) meals for seven days each. Using a portable urinary Na/K meter, participants measured their spot urine at each voiding, and 24-h urine was collected on the last day of each diet period. On the last day of the unrestricted, low-salt, and high-salt diet periods, the group averages of the 24-h urine Na/K ratio were 4.2, 1.0, and 6.9, while the group averages of the daily mean spot urine Na/K ratio were 4.2, 1.1, and 6.6, respectively. The urinary Na/K ratio tracked changes in dietary salt intake, and reached a plateau approximately three days after each change in diet. Frequent monitoring of the spot urine Na/K ratio may help individuals adhere to an appropriate dietary Na intake.

Overlap of Post-obstructive Diuresis and Unmasked Diabetes Insipidus in a Case of IgG4-related Retroperitoneal Fibrosis and Tuberoinfundibular Hypophysitis: A Case Report and Review of the Literature.

The clinical picture of IgG4-related disease (IgG4-RD) is diverse because various organs can be affected. We describe the case of a 56-year-old man with acute renal failure and tuberoinfundibular hypophysitis due to IgG4-RD. Steroid therapy lowered the serum IgG4 level and ameliorated renal dysfunction, bilateral hydronephrosis and retroperitoneal fibrosis. However, polyuria from post-obstructive diuresis and unmasked central diabetes insipidus ensued. The patient's polyuria continued despite the administration of a therapeutic dose of glucocorticoid; the patient's pituitary swelling and anterior pituitary dysfunction were partially ameliorated. The pituitary swelling recurred seven months later. In patients with IgG4-RD, the manifestation of polyuria after steroid therapy should prompt suspicion of post-obstructive diuresis and the unmasking of central diabetes insipidus.

Effects of renal Na+/Ca2+ exchanger 1 inhibitor (SEA0400) treatment on electrolytes, renal function and hemodynamics in rats.

BACKGROUND: Na(+)/Ca(2+) exchanger 1 (NCX1) controls intracellular Ca(2+) concentration in various cell types. In the kidney, NCX1 is expressed mainly in the distal tubular basolateral membrane as well as in vascular smooth muscle. Tubular NCX1 is involved in Ca(2+) reabsorption, and NCX1 in renal arterioles may control intraglomerular pressure. However, the functions of renal NCX1 have not been studied in vivo. Therefore, this study examined the effects of renal NCX1 blockade on water and solute metabolism, renal function and blood pressure in rats. METHODS: Wistar-Kyoto rats were uninephrectomized, and an osmotic mini pump was implanted to infuse the remnant kidney cortex with a specific NCX1 inhibitor, SEA0400 (SEA), or vehicle for 7 days. RESULTS: Serum Ca(2+) concentration and urinary Ca(2+) excretion were similar between the vehicle- and SEA-treated groups. However, serum phosphate was significantly decreased by 8 % in the SEA group, with similar urinary phosphate excretion between the two groups. Systolic blood pressure was higher in the SEA group (117 ± 3 vs. 126 ± 1 mmHg, n = 9-11), with a 1.6-fold increase in plasma aldosterone concentration. However, SEA significantly reduced urinary protein excretion and the glomerular sectional area by 16 and 8 %, respectively. Similar experiment in spontaneously hypertensive rats produced different results. CONCLUSION: Renal SEA treatment reduced serum phosphate concentration, urinary protein and glomerular size with higher systemic blood pressure compared to control Wistar-Kyoto rats. Further study on renal NCX1 may be beneficial in delineating the pathophysiology of glomerular pressure control and calcium/phosphate regulations.

Association between lifestyle-related disorders and visceral fat mass in Japanese males: a hospital based cross-sectional study.

OBJECTIVE: This study aimed to examine the association between lifestyle-related disorders and visceral fat mass, and to estimate an appropriate cutoff value for visceral fat mass that correlated with body mass index (BMI) and waist circumference (WC). METHODS: This cross-sectional study was conducted between July 2012 and August 2013 at Bange Kosei General Hospital, in Fukushima, Japan. All study participants were adult males who had completed voluntary medical check-ups that included estimation of visceral fat mass by bioelectrical impedance analysis (BIA). Participants were without past histories of atherosclerotic complications or were not currently taking medications for lifestyle-related disorders. Multivariate analysis was performed to estimate the association between lifestyle-related disorders and quartiles of visceral fat mass. RESULTS: Of 536 total respondents, 442 were included in the analysis. Mean participant age was 56 years, and mean values of BMI, WC, and visceral fat mass were 24.1 kg/m(2), 85.9 cm, and 2.1 kg, respectively. Visceral fat mass ≥1.8 kg was positively associated with an increased prevalence of dyslipidemia, elevated blood pressure, and impaired glucose tolerance. Cutoff values that correlated with visceral fat mass (≥1.8 kg) were 85.3 cm for WC and 23.25 kg/m(2) for BMI. CONCLUSION: Visceral fat mass ≥1.8 kg was positively associated with lifestyle-related disorders and closely related to WC and BMI cutoff values used to diagnose obesity. BIA may be a useful method for assessing visceral fat mass, and these findings provide important evidence for the use of BIA in the early detection of central obesity for preventing lifestyle-related disorders.

Characteristic expressions of GABA receptors and GABA producing/transporting molecules in rat kidney.

Gamma-aminobutyric acid (GABA) is an important neurotransmitter, but recent reports have revealed the expression of GABAergic components in peripheral, non-neural tissues. GABA administration induces natriuresis and lowers blood pressure, suggesting renal GABA targets. However, systematic evaluation of renal GABAergic components has not been reported. In this study, kidney cortices of Wistar-Kyoto rats (WKY) were used to assay for messenger RNAs of GABA-related molecules using RT-PCR. In WKY kidney cortex, GABAA receptor subunits, α1, ß3, δ, ε and π, in addition to both types of GABAB receptors, R1 and R2, and GABAC receptor ρ1 and ρ2 subunit mRNAs were detected. Kidney cortex also expressed mRNAs of glutamate decarboxylase (GAD) 65, GAD67, 4-aminobutyrate aminotransferase and GABA transporter, GAT2. Western blot and/or immunohistochemistry were performed for those molecules detected by RT-PCR. By immunofluorescent observation, co-staining of α1, ß3, and π subunits was observed mainly on the apical side of cortical tubules, and immunoblot of kidney protein precipitated with π subunit antibody revealed α1 and ß3 subunit co-assembly. This is the first report of GABAA receptor π subunit in the kidney. In summary, unique set of GABA receptor subunits and subtypes were found in rat kidney cortex. As GABA producing enzymes, transporters and degrading enzyme were also detected, a possible existence of local renal GABAergic system with an autocrine/paracrine mechanism is suggested.