Discovery and evaluation of a novel 18F-labeled vasopressin 1a receptor PET ligand with peripheral binding specificity.

The arginine-vasopressin (AVP) hormone plays a pivotal role in regulating various physiological processes, such as hormone secretion, cardiovascular modulation, and social behavior. Recent studies have highlighted the V1a receptor as a promising therapeutic target. In-depth insights into V1a receptor-related pathologies, attained through in vivo imaging and quantification in both peripheral organs and the central nervous system (CNS), could significantly advance the development of effective V1a inhibitors. To address this need, we develop a novel V1a-targeted positron emission tomography (PET) ligand, [18F]V1A-2303 ([18F]8), which demonstrates favorable in vitro binding affinity and selectivity for the V1a receptor. Specific tracer binding in peripheral tissues was also confirmed through rigorous cell uptake studies, autoradiography, biodistribution assessments. Furthermore, [18F]8 was employed in PET imaging and arterial blood sampling studies in healthy rhesus monkeys to assess its brain permeability and specificity, whole-body distribution, and kinetic properties. Our research indicated [18F]8 as a valuable tool for noninvasively studying V1a receptors in peripheral organs, and as a foundational element for the development of next-generation, brain-penetrant ligands specifically designed for the CNS.

Discovery of 18F Labeled AZD5213 Derivatives as Novel Positron Emission Tomography (PET) Radioligands Targeting Histamine Subtype-3 Receptor.

The histamine subtype 3 (H3) receptor is an important drug target in the central nervous system (CNS), and PET imaging offers a promising technique for the noninvasive evaluation of CNS disease related to the H3 receptor. In this study, we synthesized and evaluated the binding effects of [18F]H3-2404 and [18F]H3-2405 by modifying the structure of AZD5213, a selective H3 antagonist. These two radioligands were prepared in high radiochemical yields and displayed stability in serum. The in vitro autoradiographic study in rat brain tissue and the following in vivo PET studies in mice demonstrated sufficient brain uptake but predominantly non-specific distribution in rodent brain. Although these data suggest that [18F]H3-2404 and [18F]H3-2405 are unsuitable as PET tracers for brain imaging of the H3 receptor, this study provides a valuable attempt for optimizing 18F labeled radiotracers based on AZD5213.

Radiosynthesis and Evaluation of 11C-Labeled Isoindolone-Based Positive Allosteric Modulators for Positron Emission Tomography Imaging of Metabotropic Glutamate Receptor 2.

The metabotropic glutamate receptor 2 (mGluR2) has emerged as a potential therapeutic target for the treatment of various neurological diseases, prompting substantial interest in the development of mGluR2-targeted drug candidates. As part of our medicinal chemistry program, we synthesized a series of isoindolone derivatives and assessed their potential as mGluR2 positive allosteric modulators (PAMs). Notably, AZ12559322 exhibited high affinity (K i mGluR2 = 1.31 nM) and an excellent in vitro binding specificity of 89% while demonstrating selectivity over other mGluR subtypes (>4000-fold). Autoradiography with the radiolabeled counterpart, [3H]AZ12559322, revealed a heterogeneous accumulation with the highest binding in mGluR2-rich brain regions. Radioligand binding was significantly reduced by pretreatment with nonradioactive mGluR2 PAMs in brains of rats and nonhuman primates. Although positron emission tomography imaging of [11C]AZ12559322 (6a) revealed low brain uptake in a nonhuman primate, this study provides valuable guidance to further design novel isoindolone-based mGluR2 PAMs with improved brain exposure.

Preclinical Evaluation of Azabenzimidazole-Based PET Radioligands for γ-8 Dependent Transmembrane AMPA Receptor Regulatory Protein Imaging.

AMPA glutamate receptors (AMPARs) play a pivotal role in excitatory neurotransmission, particularly in the hippocampus where the TARP γ-8 subunit is enriched and serves as a target for emerging anti-epileptic drugs. To enable in vivo visualization of TARP γ-8 distribution and expression by positron emission tomography (PET), this study focuses on the development of novel 18 F-labeled TARP γ-8 inhibitors and their corresponding precursors, stemming from the azabenzimidazole scaffold. The resulting radioligands [18 F]TARP-2204 and [18 F]TARP-2205 were successfully synthesized with acceptable radiochemical yield, high molar activity, and excellent radiochemical purity. In vitro autoradiography demonstrates high level of specific binding of [18 F]TARP-2205 to TARP γ-8 in both rat and nonhuman primate brain tissues. However, unexpected radiodefluorination in PET imaging studies of rodents emphasizes the need for further structural refinement. This work serves as an excellent starting point for the development of future 18 F-labeled TARP γ-8 PET tracers, offering valuable insights into medicinal chemistry design, radiosynthesis and subsequent PET evaluation.

Synthesis and Biological Evaluation of Enantiomerically Pure (R)- and (S)-[18F]OF-NB1 for Imaging the GluN2B Subunit-Containing NMDA Receptors.

GluN2B subunit-containing N-methyl-d-aspartate (NMDA) receptors have been implicated in various neurological disorders. Nonetheless, a validated fluorine-18 labeled positron emission tomography (PET) ligand for GluN2B imaging in the living human brain is currently lacking. The aim of this study was to develop a novel synthetic approach that allows an enantiomerically pure radiosynthesis of the previously reported PET radioligands (R)-[18F]OF-NB1 and (S)-[18F]OF-NB1 as well as to assess their in vitro and in vivo performance characteristics for imaging the GluN2B subunit-containing NMDA receptor in rodents. A novel synthetic approach was successfully developed, which allows for the enantiomerically pure radiosynthesis of (R)-[18F]OF-NB1 and (S)-[18F]OF-NB1 and the translation of the probe to the clinic. While both enantiomers were selective over sigma2 receptors in vitro and in vivo, (R)-[18F]OF-NB1 showed superior GluN2B subunit specificity by in vitro autoradiography and higher volumes of distribution in the rodent brain by small animal PET studies.

Evaluation of [18F]RoSMA-18-d6 as a CB2 PET Radioligand in Nonhuman Primates.

The cannabinoid type 2 receptor (CB2) has been implicated in a variety of central and peripheral inflammatory diseases, prompting significant interest in the development of CB2-targeted diagnostic and therapeutic agents. A validated positron emission tomography (PET) radioligand for imaging CB2 in the living human brain as well as in peripheral tissues is currently lacking. As part of our research program, we have recently identified the trisubstituted pyridine, [18F]RoSMA-18-d6, which proved to be highly suitable for in vitro and in vivo mapping of CB2 in rodents. The aim of this study was to assess the performance characteristics of [18F]RoSMA-18-d6 in nonhuman primates (NHPs) to pave the way for clinical translation. [18F]RoSMA-18-d6 was synthesized from the respective tosylate precursor according to previously reported procedures. In vitro autoradiograms with NHP spleen tissue sections revealed a high binding of [18F]RoSMA-18-d6 to the CB2-rich NHP spleen, which was significantly blocked by coincubation with the commercially available CB2 ligand, GW405833 (10 µM). In contrast, no specific binding was observed by in vitro autoradiography with NHP brain sections, which was in agreement with the notion of a CB2-deficient healthy mammalian brain. In vitro findings were corroborated by PET imaging experiments in NHPs, where [18F]RoSMA-18-d6 uptake in the spleen was dose-dependently attenuated with 1 and 5 mg/kg GW405833, while no specific brain signal was observed. Remarkably, we observed tracer uptake and retention in the NHP spinal cord, which was reduced by GW405833 blockade, pointing toward a potential utility of [18F]RoSMA-18-d6 in probing CB2-expressing cells in the bone marrow. If these observations are substantiated in NHP models of enhanced leukocyte proliferation in the bone marrow, [18F]RoSMA-18-d6 may serve as a valuable marker for hematopoietic activity in various pathologies. In conclusion, [18F]RoSMA-18-d6 proved to be a suitable PET radioligand for imaging CB2 in NHPs, supporting its translation to humans.

Synthesis and Biological Evaluation of Enantiomerically Pure (R)- and (S)-[18F]OF-NB1 for Imaging the GluN2B Subunit-Containing NMDA receptors.

GluN2B subunit-containing N-methyl-d-aspartate (NMDA) receptors have been implicated in various neurological disorders. Nonetheless, a validated fluorine-18 labeled positron emission tomography (PET) ligand for GluN2B imaging in the living human brain is currently lacking. As part of our PET ligand development program, we have recently reported on the preclinical evaluation of [18F]OF-NB1 - a GluN2B PET ligand with promising attributes for potential clinical translation. However, the further development of [18F]OF-NB1 is currently precluded by major limitations in the radiolabeling procedure. These limitations include the use of highly corrosive reactants and racemization during the radiosynthesis. As such, the aim of this study was to develop a synthetic approach that allows an enantiomerically pure radiosynthesis of (R)-[18F]OF-NB1 and (S)-[18F]OF-NB1, as well as to assess their in vitro and in vivo performance characteristics for imaging the GluN2B subunit-containing NMDA receptor in rodents. A two-step radiosynthesis involving radiofluorination of the boronic acid pinacol ester, followed by coupling to the 3-benzazepine core structure via reductive amination was employed. The new synthetic approach yielded enantiomerically pure (R)-[18F]OF-NB1 and (S)-[18F]OF-NB1, while concurrently circumventing the use of corrosive reactants. In vitro autoradiograms with mouse and rat brain sections revealed a higher selectivity of (R)-[18F]OF-NB1 over (S)-[18F]OFNB1 for GluN2B-rich brain regions. In concert with these observations, blockade studies with commercially available GluN2B antagonist, CP101606, showed a significant signal reduction, which was more pronounced for (R)-[18F]OF-NB1 than for (S)-[18F]OF-NB1. Conversely, blockade experiments with sigma2 ligand, FA10, did not result in a significant reduction of tracer binding for both enantiomers. PET imaging experiments with CD1 mice revealed a higher brain uptake and retention for (R)-[18F]OF-NB1, as assessed by visual inspection and volumes of distribution from Logan graphical analyses. In vivo blocking experiments with sigma2 ligand, FA10, did not result in a significant reduction of the brain signal for both enantiomers, thus corroborating the selectivity over sigma2 receptors. In conclusion, we have developed a novel synthetic approach that is suitable for upscale to human use and allows the enantiomerically pure radiosynthesis of (R)-[18F]OF-NB1 and (S)-[18F]OF-NB1. While both enantiomers were selective over sigma2 receptors in vitro and in vivo, (R)-[18F]OF-NB1 showed superior GluN2B subunit specificity by in vitro autoradiography and higher volumes of distribution in small animal PET studies.

Silent Sigmoid Colon Diverticular Perforation: A Case Report.

Colonic perforation is associated with high mortality rates, and it requires prompt diagnosis and intervention to ensure favorable patient outcomes. The condition usually presents with typical peritoneal signs and symptoms, but atypical presentations can be a diagnostic challenge. In this report, we present a case of sigmoid diverticulosis perforation in an elderly patient who had no symptoms after the perforation developed. This case highlights the importance of detailed history, physical examination, and a low threshold of suspicion in patients with risk factors for atypical presentations.

Does Early Endoscopy Improve Mortality in Patients with Acute Non-variceal Gastrointestinal Bleeding? A Retrospective review.

Introduction Initial management of acute upper gastrointestinal bleeding (UGIB) aims towards aggressive fluid resuscitation to maintain hemodynamic stability. Existing evidence regarding the benefit of early endoscopy is unclear with some studies suggesting mortality benefits and some suggesting otherwise. The purpose of this study is to evaluate if there is any mortality benefit of doing early endoscopy within 24 hours of presentation. Methods From July 2013 to July 2016, 179 patients admitted with a diagnosis of non-variceal UGIB were retrospectively reviewed. Clinical variables including 30-day mortality were then compared between the patients who had endoscopy within 24 hours with those who had endoscopy after greater than 24 hours. Results Out of 179 patients admitted for non-variceal UGIB, 146 underwent endoscopy within 24 hours of presentation and 33 underwent endoscopy after 24 hours. The overall mortality associated with UGIB was 6.7% (12/179). There was no statistically significant difference found in 30-day mortality between the two groups (6.8% within 24 hours vs 6.1% after 24 hours). There was also no difference in 30-day readmission or rates of rebleeding among the two groups. The length of stay was also similar in both groups (6.0 days vs 6.1 days). Conclusion This study did not find any advantage of endoscopy within 24 hours on length of stay, rate of complications, and 30-day mortality. As hemostasis is achieved in almost 90% of patients with supportive management without any endoscopic intervention, focus should be made on aggressive fluid resuscitation to achieve hemodynamic stability before endoscopy.

Allopurinol-Induced Granulomatous Hepatitis: A Case Report and Review of Literature.

Liver enzyme elevation is a common reason for referral to a gastroenterologist. Drugs are one of the most common reasons for asymptomatic elevation of liver enzymes. We present here a case of granulomatous hepatitis (GH) secondary to long-term use of allopurinol. An 83-year-old male with a history of chronic gout and hypertension was evaluated for elevation of liver enzymes. He denies any complaints of abdominal pain, nausea, fever, chills, weight loss, night sweats, or yellowness of skin. He denies any use of herbal medications. He was on losartan and allopurinol for years. No new medications reported. Physical examination was unremarkable. Labs showed aspartate transaminase 101 U/L, alanine transaminase 81 U/L, and alkaline phosphatase 645 U/L. Ultrasound of the abdomen showed coarse liver texture. Liver biopsy was done that showed mixed GH. Given negative autoimmune and viral serologies, allopurinol-induced GH was suspected. Allopurinol was held, and repeat liver enzymes were checked in 3 months, which showed improvement in transaminase and alkaline phosphatase levels. This case highlights the importance of reviewing medications carefully when evaluating a patient with liver enzymes elevation, as stopping the offending drug can normalize the abnormalities in liver chemistries and can prevent subsequent expensive testing.

Does Right Ventricular Dysfunction Predict Mortality in Hemodynamically Stable Patients With Acute Pulmonary Embolism?

BACKGROUND: Acute pulmonary embolism (APE) is directly responsible for 100,000 deaths annually. Right ventricular dysfunction (RVD) on admission is considered a poor prognostic factor in these patients, though existing evidence of its significance in predicting mortality in hemodynamically stable patients is still unclear. We attempted to clarify this association by doing a retrospective review. METHODS: We retrospectively reviewed electronic medical records of hemodynamically stable patients older than 18 years of age with APE who were admitted to a tertiary care hospital in rural Upstate New York from July 2014 to July 2016. One hundred thirty-four patients were reviewed in two groups: patients who presented with computed tomography (CT) or echocardiographic evidence of RVD, and those without RVD. To identify differences in mortality between the two groups, the Chi-square/Fisher's exact test and t-tests were used. All variables with P < 0.2 in the initial analysis were included in a stepwise multivariable logistic regression model to predict RVD. RESULTS: No statistically significant difference was found in 30-day mortality between the groups (7.8% in RVD and 5.3% in no RVD, P = 0.563). The overall prevalence of RVD was found to be 57% (77/134). Troponin elevation (53.2% in RVD group vs. 19.3 in the no RVD group with P < 0.01) and central location of thrombus (53.1% vs. 32.1% with P = 0.016) were more prevalent in RVD group. A marginally significant difference was found in length of hospital stay among those with RVD versus no RVD (7.13 days vs. 5.46 days; P = 0.061). The multivariable analysis shows that the odds of RVD were greater for patients with elevated troponin levels (odds ratio = 7.8). CONCLUSION: There was no difference in 30-day mortality in hemodynamically stable patients with APE having RVD compared to patients with no RVD. On the basis of this study, we do not suggest the routine use of systemic fibrinolysis in hemodynamically stable patients with radiographic evidence of RVD alone.

Prognostic Significance of Elevated Cardiac Troponin in Acute Gastrointestinal Bleeding.

BACKGROUND: Acute gastrointestinal bleeding (AGIB) is responsible for over 140,000 hospitalizations annually. Cardiovascular-related deaths account for 30% of the patients surviving the initial episode of AGIB. The purpose of this study was to identify the impact of elevated troponin on short-term mortality and length of stay (LOS) of these patients. METHODS: From July 2013 to July 2016, 290 patients admitted with a diagnosis of AGIB and who had cardiac troponin I measured within 24 h of presentation were retrospectively reviewed. Clinical variables including 30-day mortality, 30-day readmission and LOS were then compared between the groups of troponin elevation and no troponin elevation. RESULTS: The overall 30-day mortality among patients with AGIB was 6.5% (19/290). Cardiac troponin was elevated in 10% of patients (29/290). Among patients with normal troponin, 5% (13/261) died within 30 days. In patients with troponin elevation, 21% died in the same period (6/29, P = 0.001). The LOS was also higher in patients with troponin elevation (6 vs. 5 days, P = 0.02). There was no difference in 30-day readmission among the two groups. Past history of coronary artery disease, congestive heart failure, hypertension, aspirin use and elevated creatinine was more common in patients with troponin elevation. On multivariate analysis, troponin elevation on presentation is associated with increased mortality (odds: 5.50, CI: 1.73 - 17.47, P = 0.004). CONCLUSION: In patients admitted to the inpatient service with AGIB, elevated troponin I on presentation is associated with high short-term mortality and longer hospital stay.

Recurrent Metatarsal Fractures in Postmenopausal Woman With Low Serum Alkaline Phosphatase: A Rare Diagnosis Not to Miss.

Hypophosphatasia (HPP) is a rare inborn error of metabolism due to a loss-of-function mutation in the gene for tissue nonspecific isoenzyme of alkaline phosphatase (ALP) that results in low levels of ALP. The clinical presentation of HPP is variable and in adults can easily be misdiagnosed as other forms of osteomalacia. We present a case of a 53-year-old Caucasian female who was evaluated for recurrent metatarsal fractures. She reported her first metatarsal fracture at age 21, and since then had at least 8 more metatarsal fractures over her lifetime, most without injury other than weight bearing. She reported history of gait disturbance as a child and dental issues (spacing and loosening). Laboratory tests showed normal serum calcium, phosphorus, and parathyroid hormone, but low serum ALP <20 IU/L and elevated N-telopeptide. Foot X-ray showed several healed and nonhealed metatarsal fractures, and bone densitometry revealed osteopenia. She was treated with calcium and vitamin D. A year later she had a new metatarsal fracture and a nontraumatic pelvic fracture. Teriparatide therapy was attempted but not tolerated. Due to suspicion of HPP vitamin B6 levels were checked and found to be elevated at 263 µg/L. Given her clinical presentation and low ALP levels with elevated vitamin B6, the diagnosis of HPP was made. Clinicians should be attentive to a history of recurrent low trauma fractures, premature loss of deciduous teeth, and persistently low serum ALP to suspect this diagnosis. Early case detection with the availability of recent Food and Drug Administration-approved asfotase alfa may avoid years of undiagnosed morbidity.

Acute Pancreatitis Secondary to Severe Hypertriglyceridemia: Management of Severe Hypertriglyceridemia in Emergency Setting.

Hypertriglyceridemia (HTG) is the third most common cause of acute pancreatitis (AP). The incidence of AP is around 10-20% with levels > 2,000 mg/dL. We present here a case of a 44-year-old male with history of uncontrolled diabetes mellitus and HTG admitted with severe abdominal pain. Labs revealed elevated lipase and amylase. CT of abdomen with contrast showed AP. He was found to have a triglyceride (TG) level of 6,672 mg/dL. Besides conventional treatment for AP with intravenous (IV) hydration, he was started on IV regular insulin along with dextrose saline. He had marked improvement in his TG level the next day. He was continued on insulin and dextrose saline with hourly glucose monitoring until TG was < 500 mg/dL. He was discharged on statins and fenofibrate. The goal of management of AP secondary to severe HTG in emergency setting is to lower the TG levels to less than 500 as quickly as possible as lower levels are associated with good clinical outcomes. Apheresis and IV insulin are both helpful in lowering TG levels with no randomized controlled trials showing greater efficacy of one over other. Further episodes of AP can be prevented by lifestyle modification and lipid lowering drugs to keep TG levels below 500 mg/dL. Fibrates are first-line drugs to lower TG and used either alone or in conjunction with statins. Periodic plasmapheresis can also be considered in some non-compliant patients with recurrent episodes of pancreatitis.

Cronkhite-Canada Syndrome: A Rare Cause of Chronic Diarrhea.

Cronkhite-Canada syndrome (CCS) is a rare non-hereditary disease characterized by chronic diarrhea, diffuse intestinal polyposis and onychodystrophy. We present here a case of a middle-aged female who presented with chronic intermittent bloody diarrhea associated alopecia and loss of finger and toe nails. Labs were remarkable for microcytic anemia and severe hypoalbuminemia. Endoscopy showed numerous polyps scattered throughout the colon. She was treated with nutritional support and corticosteroid with complete resolution of her symptoms and endoscopic findings. CCS is associated with high mortality and gastrointestinal malignancies. Clinicians should consider CCS in a patient with unexplained chronic diarrhea and ectodermal abnormalities.

Refractory Celiac Disease Successfully Treated With Azathioprine.

Refractory celiac disease (CD) is a clinical diagnosis defined by the persistence of signs/symptoms, laboratory abnormalities or villous atrophy typical of CD despite strict adherence to a gluten-free diet for at least 6 - 12 months. It should be suspected when patients with CD fail to respond primarily or secondarily to a gluten-free diet, especially if there is significant weight loss. Differentiation between types is important both for management and predicting prognosis. Type I can be managed with mild immunosuppression with nutritional support. Type II requires strong immunosuppression like azathioprine. Recently, autologous stem cell transplantation has also been used to treat type II.

Association of Autoimmune Hepatitis and Celiac Disease: Role of Gluten-Free Diet in Reversing Liver Dysfunction.

Autoimmune hepatitis (AIH) is a chronic inflammation of liver with unclear etiology. It is frequently associated other autoimmune diseases, and its association with celiac disease (CD) is well established. In this article, we describe the case of a 50-year-old male with long-standing AIH taking azathioprine for 10 years, evaluated for flares in transaminases. Despite adding high-dose corticosteroids, his transaminases and bilirubin remained high. Serology for CD was ordered, which revealed elevated tissue transglutaminase antibody IgG and endomysial IgA, which was further confirmed by endoscopic biopsy. Strict gluten-free diet was advised and now for over 2 years he is in remission with azathioprine and budesonide. This emphasizes the role of gluten-free diet in reversing liver dysfunction in patients with AIH, and clinicians should consider screening for CD in patients with AIH with persistent elevation of liver enzymes despite immunosuppressant treatment.

Does Syncope Predict Mortality in Patients With Acute Pulmonary Embolism? A Retrospective Review.

BACKGROUND: Acute pulmonary embolism (APE) is a potentially fatal disease with high mortality. Prior studies have shown an increased frequency of central localization of the clot, right ventricular dysfunction and elevated troponin in patients who present with syncope and APE. Existing evidence regarding mortality and length of hospital stay in these patients is unclear. METHODS: We retrospectively reviewed electronic medical records of patients who were admitted in a tertiary care hospital in rural Upstate New York and diagnosed with APE from July 2014 to July 2016. Two hundred nineteen patients were reviewed in two groups: patients who presented with syncope and those without syncope. RESULTS: The prevalence of syncope was found to be 6.8% (15/219). Hypotension on admission was more common among patients with syncope compared to no syncope (26.7% and 7.4%, respectively, P = 0.03). A clinically significant difference was found in 30-day mortality among those with syncope versus no syncope (21.3% vs. 7.4%, P = 0.096). No significant difference was found in length of stay (mean 6.7 days in patients with syncope vs. 6.4 without syncope, P = 0.783), central localization (26.7% with syncope vs. 43.2% without syncope, P = 0.21) or troponin elevation (46.2% in patients with syncope vs. 27.9% without syncope, P = 0.205). On multivariable analysis, hypotension was significantly higher among those with syncope (odds ratio: 5.23, P = 0.0148). CONCLUSION: This study suggests 30-day mortality may be higher among patients with syncope. It is important to risk stratify patients on admission in order to reduce mortality and morbidity associated with lethal disease.

Salicylate-induced pulmonary edema--a near-miss diagnosis.

A 43-year-old white woman presented to the emergency department with confusion, agitation, and progressive dyspnea. Chest x-ray revealed pulmonary edema. Initial diagnostic considerations were pneumonia, pulmonary embolism, sepsis, central nervous system infection, substance toxicity, and heart failure. Her salicylate level was 92.6 mg/dL, and an arterial blood gas revealed a respiratory alkalosis and nonanion gap metabolic acidosis, consistent with salicylate poisoning. Noncardiogenic pulmonary edema is an atypical presentation of salicylate toxicity, and this case highlights the importance of an early toxicology screen to make a time-critical diagnosis and provide specific treatment.

Aldosterone induces mesangial cell apoptosis both in vivo and in vitro.

Both clinical and experimental reports indicate that aldosterone contributes to the progression of renal failure independent of its hemodynamic effects. In the present study, we evaluated effect of aldosterone on human mesangial cell (MC) growth. Aldosterone induced apoptotic and mitogenic effects on MCs. Aldosterone promoted MC apoptosis in a dose- and time-dependent manner. Spironolactone, a mineralocorticoid receptor antagonist, inhibited aldosterone-induced MC apoptosis. Similarly, antioxidants and free radical scavengers partially attenuated proapoaptotic effects of aldosterone. Aldosterone also enhanced dephosphorylation of phospho-Bad and accumulation of cytosolic cytochrome c in MCs. In in vivo studies, rats were randomly assigned to receive normal saline, aldosterone, or eplerenone + aldosterone for 28 days. Systolic blood pressure, urinary albumin excretion rate, serum creatinine, and aldosterone were measured. Aldosterone-infused rats developed elevated systolic blood pressure and albuminuria when compared with control rats. Aldosterone-treated rats also showed greater numbers of apoptosed MCs. This proapoptotic effect of aldosterone was inhibited by eplerenone, a selective aldosterone antagonist. These findings suggest that aldosterone, besides its hemodynamic effects, may also directly contribute to the occurrence of MC apoptosis.