Glycyrrhetinic acid as inhibitor or amplifier of permeability transition in rat heart mitochondria

Revisiting Licorice as a functional food in the management of neurological disorders: Bench to trend

Traditional and scientific evidence attribute numerous bioactivities of Licorice (Glycyrrhiza glabra Linn.) in aging-related disorders. In this state-of-art review, an extensive search in several databases was conducted to collect all relevant literature and comprehensively analyze Licorice's pharmacological attributes, neuroprotective properties, safety, and its mechanistic role in treating various neurological conditions. Network pharmacology was employed for the first time exploring the mechanistic role of Licorice in neurological disorders. Its neuroprotective role is attributed to phytoconstituents, including liquiritin, glycyrrhizic acid, liquiritigenin, glabridin, 18ß-glycyrrhetinic acid, quercetin, isoliquiritigenin, paratocarpin B, glycyglabrone, and hispaglabridin B, as evident from in vitro and in vivo studies. Network pharmacology analysis reveals that these compounds protect against long-term depression, aging-associated diseases, Alzheimer's disease, and other addictions through interactions with cholinergic, dopaminergic, and serotonergic proteins, validated in animal studies only. Future clinical trials are warranted as Licorice administration has a limiting factor of mild hypertension and hypokalemia. Hopefully, scientific updates on Licorice will propagate a paradigm shift in medicine, research propagation, and development of the central nervous system phytopharmaceuticals.

To Explore the Key Active Compounds and Therapeutic Mechanism of Guizhi Gancao Decoction in Coronary Heart Disease by Network Pharmacology and Molecular Docking

Objective. Coronary heart disease (CHD) is the leading cause of death from cardiovascular disease and has become an important public health problem worldwide. Guizhi Gancao Decoction (GGD) has been shown to be used in the treatment of CHD with good efficacy, but its specific therapeutic mechanism and active ingredients have not been fully clarified. This study aims to identify the active compounds and key targets of GGD in the treatment of CHD, explore the therapeutic mechanism of GGD, and provide candidate compounds for anti-CHD drug development. Methods. The main compounds of GGD were determined by UPLC-MS/MS analysis and screened by SwissADME. The corresponding targets of GGD compounds were obtained from SwissTargetPrediction, and the targets of CHD were obtained from the HERB and GeneCards databases. The STRING 11.5 database was used to analyze the PPI (Protein-Protein Interactions) network of potential therapeutic targets of GGD compounds. Cytoscape 3.7.2 was used to construct target-related networks and find core targets. The GEO database was used to validate the differential expression of core targets. The PANTHER Classification System was used to functionally classify potential therapeutic targets for GGD. The GO biological process analysis and KEGG pathway analysis of targets were completed by DAVID 6.8 database. AutoDockTools 1.5.6 and PyMol 2.5.2 were used to perform molecular docking of core targets with the active GGD compounds. Results. 7 active GGD compounds were obtained based on UPLC-MS/MS and pharmacological parameter evaluation, which corresponded to 131 CHD-related targets. Among them, EGFR, MAPK3, RELA, CCND1, ESR1, PTGS2, NR3C1, CYP3A4, MMP9, and PTPN11 were considered core targets. According to the targets related to CHD, glycyrrhetinic acid, liquiritigenin, and schisandrin are considered key active ingredients. GO biological process and KEGG analysis indicated that the potential targets of GGD in the treatment of CHD involve a variety of biological processes and therapeutic mechanisms. Molecular docking results showed that both the core targets and the corresponding compounds had the good binding ability. Conclusions. This study contributes to a more comprehensive understanding of the therapeutic mechanism and active ingredients of GGD for CHD and provides candidate compounds for drug development of CHD.

Detection of Herbal Combinations and Pharmacological Mechanisms of Clinical Prescriptions for Coronary Heart Disease Using Data Mining and Network Pharmacology

Though widely used in the treatment of coronary heart disease (CHD), the mechanism of traditional Chinese medicine (TCM) is still unclear because of its complex prescription rules. This study prospectively collected 715 prescriptions of TCM for the treatment of CHD. The characteristics of TCM in prescriptions were described and analyzed, and the rules of prescriptions were analyzed by using association rules. Frequency statistics showed that the high-frequency herbs with a frequency of more than 60% were Gan-cao, Huang-qi, Dang-gui, Chuan-xiong, Yan-hu-suo, and San-qi. The high-frequency herb combinations were summarized by using association rules. By using the method of the “Top N groups” to excavate the empirical prescriptions, the basic prescriptions for treating CHD were summarized. We named the intersection herbs of the basic prescriptions and the high frequency herbs as the core herbal prescription. To explore the possible mechanisms underlying the anti-CHD effect of the core herbal prescription, the bioactive components of core herbal prescription and their targets were screened out by using network pharmacology. Molecular docking was performed between the bioactive components and core targets. A total of 28 potential active ingredients and 5 core targets were identified for the treatment of CHD with core herbal prescription. The enrichment analysis results indicated that the mechanism of action mainly involved neuroactive ligand-receptor interaction and calcium signaling pathway. The commonly used herbal pairs for CHD with qi deficiency and blood stasis syndrome were Huang-qi and Dang-gui. The mechanism of action of common herbal pairs was also studied by network pharmacology. This study summarized the prescription rule of TCM in the treatment of CHD and may provide a new idea for the treatment of CHD.

Preclinical Evidence for the Pharmacological Actions of Glycyrrhizic Acid: A Comprehensive Review

Glycyrrhiza glabra L. (Family: Fabaceae) is one of the important traditional medicinal plant used extensively in folk medicine. It is known for its ethnopharmacological value in curing a wide variety of ailments. Glycyrrhizin, an active compound of G. glabra, possesses anti-inflammatory activity due to which it is mostly used in traditional herbal medicine for the treatment and management of chronic diseases. The present review is focused extensively on the pharmacology, pharmacokinetics, toxicology, and potential effects of Glycyrrhizic Acid (GA). A thorough literature survey was conducted to identify various studies that reported on the GA on PubMed, Science Direct and Google Scholar.

Study on Medication Rules of Traditional Chinese Medicine against Antineoplastic Drug-Induced Cardiotoxicity Based on Network Pharmacology and Data Mining

Methods

The targets of antineoplastic drugs with cardiotoxicity were obtained from the National Center for Biotechnology Information (NCBI) database, China national knowledge infrastructure (CNKI) database, and Swiss Target Prediction platform. Then, the cardiotoxicity-related targets were derived from the Gene Cards, Disgenet, OMIM, and DrugBank databases, as well as the drug of current clinical guidelines. The targets both in these two sets were regarded as potential targets to alleviate ADIC. Then, candidate compounds and herbs were matched via Traditional Chinese Medicine Systems Pharmacology (TCMSP) platform. Cytoscape3.7.1 was used to set up the target-compound-herb network. Molecular docking between core targets and compounds was performed with AutodockVina1.1.2. The rules of herbs were summarized by analyzing their property, flavor, and channel tropism.

Results

Twenty-one potential targets, 332 candidate compounds, and 400 kinds of herbs were obtained. Five core targets including potassium voltage-gated channel subfamily H member 2 (KCNH2), cyclin-dependent kinase 1 (CDK1), matrix metalloproteinase 2 (MMP2), mitogen-activated protein kinase1 (MAPK1), and tumor protein p53 (TP53) and 29 core compounds (beta-sitosterol, quercetin, kaempferol, etc.) were collected. Five core herbs (Yanhusuo, Gouteng, Huangbai, Lianqiao, and Gancao) were identified. Also, the TCM against ADIC were mainly bitter and acrid in taste, warm in property, and distributed to the liver and lung meridians.

Conclusion

TCM against ADIC has great potential. Our study provides a new method and ideas for clinical applications of integrated Chinese and western medicine in treating ADIC.

The antioxidant, aged garlic extract, exerts cytotoxic effects on wild-type and multidrug-resistant human cancer cells by altering mitochondrial permeability

Aged garlic extract (AGE) has been shown to possess therapeutic properties in cancer; however its mechanisms of action are unclear. In this study, we demonstrate by MTT assay that AGE exerts an anti-proliferative effect on a panel of both sensitive and multidrug-resistant (MDR) human cancer cell lines and enhances the effects of hyperthermia (42˚C) on M14 melanoma cells. The evaluation of the mitochondrial activity in whole cancer cells treated with AGE, performed by cytofluorimetric analysis in the presence of the lipophilic cationic fluorochrome JC-1, revealed the occurrence of dose-dependent mitochondrial membrane depolarization. Membrane potential was measured by the TPP+ selective electrode. In order to shed light on its mechanisms of action, the effects of AGE on isolated rat liver mitochondria were also examined. In this regard, AGE induced a mitochondrial membrane hyperpolarization of approximately 15 mV through a mechanism that was similar to that observed with the ionophores, nigericin or salinomycin, by activating an exchange between endogenous K+ with exogenous H+. The prolonged incubation of the mitochondria with AGE induced depolarization and matrix swelling, indicative of mitochondrial permeability transition induction that, however, occurs through a different mechanism from the well-known one. In particular, the transition pore opening induced by AGE was due to the rearrangement of the mitochondrial membranes following the increased activity of the K+/H+ exchanger. On the whole, the findings of this study indicate that AGE exerts cytotoxic effects on cancer cells by altering mitochondrial permeability. In particular, AGE in the mitochondria activates K+/H+ exchanger, causes oxidative stress and induces mitochondrial permeability transition (MPT).

Protective Effect of 18β-Glycyrrhetinic Acid against Triptolide-Induced Hepatotoxicity in Rats

Triptolide (TP) is the major active component of Tripterygium wilfordii Hook F (TWHF) and possesses multiple pharmacological effects. However, hepatotoxicity of TP which is one of the toxic properties slows its progression in clinical application. 18β-Glycyrrhetinic acid (GA) is the main bioactive ingredient of Licorice (Glycyrrhiza glabra L.), a herbal medicine famous for its detoxification. This study aims to investigate whether GA possesses protective effect against TP-induced hepatotoxicity in rats. TP interference markedly elevated serum levels of ALT, AST, and ALP, caused evident liver histopathological changes, and elevated hepatic TNF-α, IL-6, IL-1β, and IFN-γ as well as nuclear translocation of NF-κB. TP also significantly elevated liver MDA and declined hepatic activities of SOD, CAT, and GSH-Px. Assay of TUNEL and apoptosis proteins (Bax, Bcl-2, and active caspase-3) showed that TP induced severe hepatocellular apoptosis. In contrast, low-dose GA (50 mg/kg) significantly reversed TP-induced changes above. However, high-dose GA (100 mg/kg) had no such effect. Overall, these findings indicated that low-dose GA but not high-dose GA exhibited a protective effect against TP-induced hepatotoxicity in rats by anti-inflammation, antioxidation, and antiapoptosis, which suggests that the doses of GA/Licorice should be carefully considered when used together with TWHF or TWHF preparations.

Mitochondrial Cx43 hemichannels contribute to mitochondrial calcium entry and cell death in the heart

Mitochondrial connexin 43 (Cx43) plays a key role in cardiac cytoprotection caused by repeated exposure to short periods of non-lethal ischemia/reperfusion, a condition known as ischemic preconditioning. Cx43 also forms calcium (Ca²⁺)-permeable hemichannels that may potentially lead to mitochondrial Ca²⁺ overload and cell death. Here, we studied the role of Cx43 in facilitating mitochondrial Ca²⁺ entry and investigated its downstream consequences. To that purpose, we used various connexin-targeting peptides interacting with extracellular (Gap26) and intracellular (Gap19, RRNYRRNY) Cx43 domains, and tested their effect on mitochondrial dye- and Ca²⁺-uptake, electrophysiological properties of plasmalemmal and mitochondrial Cx43 channels, and cell injury/cell death. Our results in isolated mice cardiac subsarcolemmal mitochondria indicate that Cx43 forms hemichannels that contribute to Ca²⁺ entry and may trigger permeability transition and cell injury/death. RRNYRRNY displayed the strongest effects in all assays and inhibited plasma membrane as well as mitochondrial Cx43 hemichannels. RRNYRRNY also strongly reduced the infarct size in ex vivo cardiac ischemia-reperfusion studies. These results indicate that Cx43 contributes to mitochondrial Ca²⁺ homeostasis and is involved in triggering cell injury/death pathways that can be inhibited by RRNYRRNY peptide.

NMR-based metabonomics study on the effect of Gancao in the attenuation of toxicity in rats induced by Fuzi

ETHNOPHARMACOLOGICAL RELEVANCE

Fuzi, the processed lateral root of Aconitum carmichaelii Debeaux, is a traditional Chinese medicine used for its analgesic, antipyretic, anti-rheumatoid arthritis and anti-inflammation effects; however, it is also well known for its toxicity. Gancao, the root of Glycyrrhiza uralensis Fisch., is often used concurrently with Fuzi to alleviate its toxicity. However, the mechanism of detoxication is still not well clear.

AIM OF THE STUDY

In this study, the effect of Gancao on the metabolic changes induced by Fuzi was investigated by NMR-based metabonomic approaches.

MATERIALS AND METHODS

Fifty male Wistar rats were randomly divided into five groups (group A: control, group B: Fuzi decoction alone, group C: Gancao decoction alone, group D: Fuzi decoction and Gancao decoction simultaneously, group E: Fuzi decoction 5h after Gancao decoction) and urine samples were collected for NMR-based metabolic profiling analysis. Statistical analyses such as unsupervised PCA, t-test, hierarchical cluster, and pathway analysis were used to detect the effects of Gancao on the metabolic changes induced by Fuzi.

RESULTS

The behavioral and biochemical characteristics showed that Fuzi exhibited toxic effects on treated rats (group B) and statistical analyses showed that their metabolic profiles were in contrast to those in groups A and C. However, when Fuzi was administered with Gancao, the metabolic profiles became similar to controls, whereby Gancao reduced the levels of trimethylamine N-oxide, betaine, dimethylglycine, valine, acetoacetate, citrate, fumarate, 2-ketoglutarate and hippurate, and regulated the concentrations of taurine and 3-hydroxybutyrate, resulting in a decrease in toxicity. Furthermore, important pathways that are known to be involved in the effect of Gancao on Fuzi, including phenylalanine, tyrosine and tryptophan biosynthesis, the synthesis and degradation of ketone bodies, and the TCA cycle, were altered in co-treated rats.

CONCLUSIONS

Gancao treatment mitigated the metabolic changes altered by Fuzi administration in rats, demonstrating that dosing with Gancao could reduce the toxicity of Fuzi at the metabolic level. Fuzi and Gancao administered simultaneously resulted in improved toxicity reduction than when Gancao was administrated 5h prior to Fuzi. In summary, co-administration of Gancao with Fuzi reduces toxicity at the metabolic level.

18α-Glycyrrhetinic Acid Induces Apoptosis of HL-60 Human Leukemia Cells through Caspases- and Mitochondria-Dependent Signaling Pathways

In this study we investigate the molecular mechanisms of caspases and mitochondria in the extrinsic and intrinsic signal apoptosis pathways in human leukemia HL-60 cells after in vitro exposure to 18α-glycyrrhetinic acid (18α-GA). Cells were exposed to 18α-GA at various concentrations for various time periods and were harvested for flow cytometry total viable cell and apoptotic cell death measurements. Cells treated with 18α-GA significantly inhibited cell proliferation and induced cell apoptosis in a dose-dependent manner, with an IC₅₀ value of 100 μM at 48 h. The cell growth inhibition resulted in induction of apoptosis and decreased the mitochondria membrane potential (ΔΨ_m) and increased caspase-8, -9 and -3 activities. Furthermore, cytochrome c and AIF were released from mitochondria, as shown by western blotting and confirmed by confocal laser microscopy. Western blotting showed that 18α-GA increased the levels of pro-apoptotic proteins such as Bax and Bid and decreased the anti-apoptotic proteins such as Bcl-2 and Bcl-xl, furthermore, results also showed that 18α-GA increased Fas and Fas-L which are associated with surface death receptor in HL-60 cells. Based on those observations, the present study supports the hypothesis that 18α-GA-induced apoptosis in HL-60 cells involves the activation of the both extrinsic and intrinsic apoptotic pathways.

Therapeutic effect of recombinant lentiviral vector containing succinate dehydrogenase iron-sulfur protein on the treatment of experimental autoimmunity myocarditis

Cardiac autoimmune reaction takes part in myocarditis, dilated cardiomyopathy and heart failure. Existing literature has confirmed that the occurrence of cardiomyopathy belongs to mitochondrial diseases and is related to the oxidative respiratory chain subunit. The special structure of iron-sulfur protein (ISP) is responsible for the oxidative stress in oxidative phosphorylation, which is also a target that is easily attacked by various damage factors. Using gene therapy technology to restore succinate dehydrogenase iron-sulfur protein (SDISP) function- and thus resume myocardial mitochondria function and myocardial function is hypothesized to alleviate the experimental autoimmunity myocarditis (EAM).

Metabonomics study of the effects of pretreatment with glycyrrhetinic acid on mesaconitine-induced toxicity in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Aconitum carmichaelii Debx. (Fuzi), a commonly use traditional Chinese medicine (TCM), has often been used in combination with Rhizoma Glycyrrhizae (Gancao) to reduce its toxicity due to diester diterpenoid alkaloids aconitine, mesaconitine, and hypaconitine. However, the mechanism of detoxication is still unclear. Glycyrrhetinic acid (GA) is the metabolite of glycyrrhizinic acid (GL), the major component of Gancao. In present study, the effect of GA on the changes of metabolic profiles induced by mesaconitine was investigated using NMR-based metabolomic approaches.

MATERIALS AND METHODS

Fifteen male Wistar rats were divided into a control group, a group administered mesaconitine alone, and a group administered mesaconitine with one pretreatment with GA. Their urine samples were used for NMR spectroscopic metabolic profiling. Statistical analyses such as orthogonal projections to latent structures-discriminant analysis (OPLS-DA), t-test, hierarchical cluster, and pathway analysis were used to detect the effects of pretreatment with GA on mesaconitine-induced toxicity.

RESULTS

The OPLS-DA score plots showed the metabolic profiles of GA-pretreated rats apparently approach to those of normal rats compared to mesaconitine-induced rats. From the t-test and boxplot results, the concentrations of leucine/isoleucine, lactate, acetate, succinate, trimethylamine (TMA), dimethylglycine (DMG), 2-oxo-glutarate, creatinine/creatine, glycine, hippurate, tyrosine and benzoate were significantly changed in metabolic profiles of mesaconitine-induced rats. The disturbed metabolic pathways include amino acid biosynthesis and metabolism.

CONCLUSIONS

GA-pretreatment can mitigate the metabolic changes caused by mesaconitine-treatment on rats, indicating that prophylaxis with GA could reduce the toxicity of mesaconitine at the metabolic level.

Inhibitory effects of glycyrrhetinic Acid on the delayed rectifier potassium current in Guinea pig ventricular myocytes and HERG channel

Background. Licorice has long been used to treat many ailments including cardiovascular disorders in China. Recent studies have shown that the cardiac actions of licorice can be attributed to its active component, glycyrrhetinic acid (GA). However, the mechanism of action remains poorly understood. Aim. The effects of GA on the delayed rectifier potassium current (I_K), the rapidly activating (I_Kr) and slowly activating (I_Ks) components of I_K, and the HERG K⁺ channel expressed in HEK-293 cells were investigated. Materials and Methods. Single ventricular myocytes were isolated from guinea pig myocardium using enzymolysis. The wild type HERG gene was stably expressed in HEK293 cells. Whole-cell patch clamping was used to record I_K (I_Kr, I_Ks) and the HERG K⁺ current. Results. GA (1, 5, and 10 μM) inhibited I_K (I_Kr, I_Ks) and the HERG K⁺ current in a concentration-dependent manner. Conclusion. GA significantly inhibited the potassium currents in a dose- and voltage-dependent manner, suggesting that it exerts its antiarrhythmic action through the prolongation of APD and ERP owing to the inhibition of I_K (I_Kr, I_Ks) and HERG K⁺ channel.

Mitochondrial connexin 43 impacts on respiratory complex I activity and mitochondrial oxygen consumption

Connexin 43 (Cx43) is present at the sarcolemma and the inner membrane of cardiomyocyte subsarcolemmal mitochondria (SSM). Lack or inhibition of mitochondrial Cx43 is associated with reduced mitochondrial potassium influx, which might affect mitochondrial respiration. Therefore, we analysed the importance of mitochondrial Cx43 for oxygen consumption. Acute inhibition of Cx43 in rat left ventricular (LV) SSM by 18α glycyrrhetinic acid (GA) or Cx43 mimetic peptides (Cx43-MP) reduced ADP-stimulated complex I respiration and ATP generation. Chronic reduction of Cx43 in conditional knockout mice (Cx43(Cre-ER(T)/fl) + 4-OHT, 5-10% of Cx43 protein compared with control Cx43(fl/fl) mitochondria) reduced ADP-stimulated complex I respiration of LV SSM to 47.8 ± 2.4 nmol O(2)/min.*mg protein (n = 8) from 61.9 ± 7.4 nmol O(2)/min.*mg protein in Cx43(fl/fl) mitochondria (n = 10, P < 0.05), while complex II respiration remained unchanged. The LV complex I activities (% of citrate synthase activity) of Cx43(Cre-ER(T)/fl) +4-OHT mice (16.1 ± 0.9%, n = 9) were lower than in Cx43(fl/fl) mice (19.8 ± 1.3%, n = 8, P < 0.05); complex II activities were similar between genotypes. Supporting the importance of Cx43 for respiration, in Cx43-overexpressing HL-1 cardiomyocytes complex I respiration was increased, whereas complex II respiration remained unaffected. Taken together, mitochondrial Cx43 is required for optimal complex I activity and respiration and thus mitochondrial ATP-production.

Interactions of melatonin with mammalian mitochondria. Reducer of energy capacity and amplifier of permeability transition

Melatonin, a metabolic product of the amino acid tryptophan, induces a dose-dependent energy drop correlated with a decrease in the oxidative phosphorylation process in isolated rat liver mitochondria. This effect involves a gradual decrease in the respiratory control index and significant alterations in the state 4/state 3 transition of membrane potential (ΔΨ). Melatonin, alone, does not affect the insulating properties of the inner membrane but, in the presence of supraphysiological Ca2+, induces a ΔΨ drop and colloid-osmotic mitochondrial swelling. These events are sensitive to cyclosporin A and the inhibitors of Ca2+ transport, indicative of the induction or amplification of the mitochondrial permeability transition. This phenomenon is triggered by oxidative stress induced by melatonin and Ca2+, with the generation of hydrogen peroxide and the consequent oxidation of sulfydryl groups, glutathione and pyridine nucleotides. In addition, melatonin, again in the presence of Ca2+, can also induce substantial release of cytochrome C and AIF (apoptosis-inducing factor), thus revealing its potential as a pro-apoptotic agent.

Glycyrrhizin and glycyrrhetinic acid directly modulate rat cardiac performance

Root extract of liquorice is traditionally used to treat several diseases. Liquorice-derived constituents present several biological actions. In particular, glycyrrhizin and its aglycone, glycyrrhetinic acid, exhibit well-known cardiovascular properties. The aim of this research was to explore the direct cardiac activity of glycyrrhizin and glycyrrhetinic acid. The effects of synthetic glycyrrhizin and glycyrrhetinic acid were evaluated on the isolated and Langendorff perfused rat heart. The intracellular signaling involved in the effects of the two substances was analyzed on isolated and perfused heart and by Western blotting on cardiac extracts. Under basal conditions, both glycyrrhizin and glycyrrhetinic acid influenced cardiac contractility and relaxation. Glycyrrhizin induced significant positive inotropic and lusitropic effects starting from very low concentrations, while both inotropism and lusitropism were negatively affected by glycyrrhetinic acid. Both substances significantly increased heart rate. Analysis of the signal transduction mechanisms suggested that glycyrrhizin acts through the endothelin receptor type A/phospholipase C axis while glycyrrhetinic acid acts through endothelin receptor type B/Akt/nitric oxide synthase/nitric oxide axis. To our knowledge, these data reveal, for the first time, that both glycyrrhizin and glycyrrhetinic acid directly affect cardiac performance. Additional information on the physiological significance of these substances and their cardiac molecular targets may provide indication on their biomedical application.

Glycyrrhetinic acid food supplementation lowers serum potassium concentration in chronic hemodialysis patients

Hyperkalemia is a common life-threatening problem in hemodialysis patients. Because glycyrrhetinic acid (GA) inhibits the enzyme 11beta-hydroxy-steroid dehydrogenase II and thereby increases cortisol availability to the colonic mineralocorticoid receptor, it has the potential to lower serum potassium concentrations. To test this, 10 patients in a 6 month prospective, double-blind, placebo-controlled crossover study were given cookies or bread rolls supplemented with glycyrrhetinic acid or placebo. Twenty-four-hour blood pressure measurements were performed at baseline and week 6 and 12 of each treatment period. The ratio of plasma cortisol/cortisone was significantly increased in all patients on GA as compared to baseline or placebo, indicating appropriate enzyme inhibition. Nine of the 10 patients had a persistent decrease in predialysis serum potassium concentration. On GA, mean predialysis serum potassium was significantly lower than at baseline or on placebo. On placebo, serum potassium was significantly elevated above the upper limit of normal in 76% compared to 30% of measurements during GA treatment. Furthermore, on this treatment the frequency of severe hyperkalemia significantly decreased from 9% to 0.6%. No differences were found in parameters reflecting sodium retention. Although these studies show that prolonged GA supplementation persistently lowers serum potassium in dialysis patients, a long-term toxicity study will be mandatory before we recommend the routine use of this treatment.