Correction: Iatrogenic Hypermagnesemia in a Patient With Preeclampsia Caused by Misinterpretation of the Magnesium Reporting Unit Following Magnesium Sulfate Administration.

[This corrects the article DOI: 10.7759/cureus.32446.].

Iatrogenic Hypermagnesemia in a Patient With Preeclampsia Caused by Misinterpretation of the Magnesium Reporting Unit Following Magnesium Sulfate Administration.

Because of the lack of standardization, different laboratories report plasma magnesium sulfate or magnesium level in different units, leading to errors in diagnosis and case management; especially when a patient's workup was done in a hospital and then transferred to another hospital. Failure to recognize or understand the reporting units can confuse clinicians and healthcare workers, leading to erroneous interpretations and, consequently, to misdiagnosis of hypermagnesemia or hypomagnesemia. In this report, we present a 32-year-old female patient at 31 weeks of gestation with a history of a multi-substance use disorder who was transferred to the hospital after taking 2.5mg of fentanyl. At the ER, her blood pressure and liver function tests were found to be high. Her albumin was 3.4 g/dl, aspartate transaminase (AST) was 104 IU/l, alanine transaminase (ALT) was 19 IU/l, and anaplastic lymphoma kinase (ALK) phosphatase was 148 IU/l; however, the renal function test was within the normal range. She had a few twitching movements. Her troponin I was high at 648 ng/L, and her B-type natriuretic peptide was 186.1 pg/mL, but her ECG showed a normal result. Magnesium was initiated on a 6 mg bolus, then 2 mg/dl due to preeclampsia concerns. She was transferred to another hospital ICU that used mEq/L as a reporting unit for magnesium and magnesium sulfate levels. The travel nurse did not alert the physician, thinking that magnesium sulfate was still within with therapeutic range of 4.8-8.4 mg/dL. However, considering 4.0-7.0 is the therapeutic range of magnesium sulfate utilizing mEq/L as a reporting unit instead of mg/dL, the patient was found to be at a supratherapeutic level, reaching up to 8.2 mEq/L. The physician discounted the magnesium sulfate. Her blood picture showed normocytic normochromic anemia. Her hemoglobin was 10.9 g/dl, her hematocrit was 33.8%, her mean corpuscular volume (MCV) was 92.5 fL, and her mean corpuscular hemoglobin (MCH) was 29.5 fL. Her platelets were within the normal range (169 10exp9/L). Her temperature was 99.6 F with increased white blood cells (17.7 10e9/L). The fetus was delivered via C-section on the third day of admission in the setting of persistently low fetal heart rates. The patient was extubated on the fourth day of admission and later transferred to the ward and discharged on the fifth day. Monitoring the magnesium level while administrating magnesium sulfate is essential to avoid iatrogenic hypermagnesemia. Utilizing different units at the same laboratory or across different laboratories could lead to the healthcare providers misinterpreting the result, which can lead to misdiagnosing iatrogenic hypermagnesemia. Therefore, standardizing magnesium units across the Clinical Laboratory Improvement Amendments (CLIA) and College of American Pathologists (CAP)-accredited laboratories is highly recommended. A unified unit reporting protocol will allow healthcare providers, constantly and correctly, to interpret the results and avoid misdiagnosing iatrogenic hypermagnesemia, and it will facilitate reporting and exchange of results among the different laboratories.

Left atrial fibrosis correlates with extent of left ventricular myocardial delayed enhancement and left ventricular strain in hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is associated with increased left ventricular (LV) mass, decreased myocardial strain, and the presence of LV fibrosis and scar. The relationship between LV scar and fibrosis with left atrial (LA) fibrosis in the setting of HCM has not been examined. The purpose of this study is to demonstrate a correlation between the degree of LA fibrosis and LV parameters in subjects with HCM. Twenty-eight subjects with HCM were imaged on a 1.5T MRI scanner with cine, LV and LA late gadolinium enhancement (LGE) sequences. LA LGE and LA measurements were correlated with LV measurements of volumes, mass, strain, and LGE. Other clinical conditions and medication usage were also examined and evaluated for correlation with LA and LV parameters. LV LGE was identified in 24 (86%) of the cases and LA LGE was identified in all of the cases. Extent of LA fibrosis significantly correlated with percent LV LGE (r = 0.64, p = 0.001), but not with indexed LV mass or maximum wall thickness. Extent of LA fibrosis also moderately correlated with decreased LV global strain (radial, r = - 0.50, p = 0.013; circumferential, r = 0.47, p = 0.02; longitudinal, r = 0.52, p = 0.013). Increased LA systolic volume correlated moderately with LV end diastolic volume (r = 0.50, p = 0.006). Patients on therapy with Renin-Angiotensin-Aldosterone System (RAAS) Inhibition had significantly less LA LGE compared to those without (18.6% vs 10.8%, p = 0.023). LA fibrosis, as measured by LGE, is prevalent in HCM and is correlated with LV LGE. The correlation between LA and LV LGE might suggest either that LA fibrosis is a consequence of LV remodeling, or that LA and LV fibrosis are both manifestations of the same cardiomyopathic process. Further study is warranted to determine the causality of LA scar in this population.

REPAIRit: Improving Myocardial Nulling and Ghosting Artifacts of 3D Navigator-Gated Late Gadolinium Enhancement Imaging During Arrhythmia.

BACKGROUND: Cardiac 3D navigator-gated late gadolinium enhancement (LGE) imaging is important for assessment of left atrial fibrosis, but the image quality is often degraded due to arrhythmia. PURPOSE: To investigate a novel 3D LGE sequence with improved myocardial nulling and reduced ghosting artifacts during arrhythmia. STUDY TYPE: Prospective. POPULATION: Arrhythmia patients (n = 14). SEQUENCE: The proposed technique, REPAIRit (Regrowth Equalization Pulse for Arrhythmias in Inversion Recovery with automatic inversion time calculation), inserts a saturation pulse with a dynamic flip angle into the 3D LGE sequence to minimize arrhythmia-induced signal fluctuations. Using ShMOLLI (shortened modified Look-Locker imaging) to estimate myocardial T1 , REPAIRit automatically calculates the optimal inversion time (TI) based on Bloch equations. ASSESSMENT: REPAIRit LGE and the standard LGE were compared with simulations, phantom imaging, and patient studies. Patient images were assessed quantitatively, based on ghost-to-noise ratio (GNR), blood signal-to-noise ratio (SNRb), myocardial signal-to-noise ratio (SNRm), and blood-to-myocardium contrast-to-noise ratio (CNR), and qualitatively on a 4-point scale. Patients were subgrouped based on the presence of arrhythmia to assess the image quality difference. STATISTICAL TESTS: The two LGE sequences were compared by Student's t-test and Wilcoxon signed-rank test. The two patient-subgroups were compared using Welch's t-test and Wilcoxon rank-sum test. RESULTS: In 14 analyzed patients, REPAIRit LGE significantly lowered GNR (1.25 ± 0.41 vs. 1.42 ± 0.42, P = 0.04), reduced SNRm (1.90 ± 0.60 vs. 3.16 ± 1.66, P = 0.01), improved ghosting artifact scores (2.5 ± 0.6 vs. 2.2 ± 0.9, P = 0.03), myocardial nulling scores (2.7 ± 0.5 vs. 2.3 ± 0.7, P = 0.02), and atrial quality scores (2.8 ± 0.3 vs. 2.4 ± 0.8, P = 0.03) compared with the standard LGE. Comparing patients with arrhythmia (n = 6) to those without (n = 8) during the scan, the former had lower left ventricular (LV) myocardial T1 s (430 ± 26 msec vs. 469 ± 39 msec, P = 0.06) but similar blood T1 s (318 ± 55 msec vs. 316 ± 27 msec, P = 0.96), and significantly lower blood SNR (5.2 ± 1.8 vs. 9.2 ± 3.0, P = 0.01) and significantly worse image quality (P = 0.01 for REPAIRit and P = 0.03 for standard). DATA CONCLUSION: REPAIRit improves myocardial nulling and reduces ghosting artifacts of 3D LGE under arrhythmia. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;49:688-699.

Reverse double inversion-recovery: Improving motion robustness of cardiac T2 -weighted dark-blood turbo spin-echo sequence.

BACKGROUND: Cardiac dark-blood turbo spin-echo (TSE) imaging is sensitive to through-plane motion, resulting in myocardial signal reduction. PURPOSE: To propose and validate reverse double inversion-recovery (RDIR)-a dark-blood preparation with improved motion robustness for the cardiac dark-blood TSE sequence. STUDY TYPE: Prospective. POPULATION: Healthy volunteers (n = 10) and patients (n = 20). FIELD STRENGTH: 1.5T (healthy volunteers) and 3T (patients). ASSESSMENT: Compared to double inversion recovery (DIR), RDIR swaps the two inversion pulses in time and places the slice-selective 180° in late-diastole of the previous cardiac cycle to minimize slice misregistration. RDIR and DIR were performed in the same left-ventricular basal short-axis slice. Healthy subjects were imaged with two preparation slice thicknesses, 110% and 200%, while patients were imaged using a 200% slice thickness only. Images were assessed quantitatively, by measuring the myocardial signal heterogeneity and the extent of dropout, and also qualitatively on a 5-point scale. STATISTICAL TESTS: Quantitative and qualitative data were assessed with Student's t-test and Wilcoxon signed-rank test, respectively. RESULTS: In healthy subjects, RDIR with 110% slice thickness significantly reduced signal heterogeneity in both the left ventricle (LV) and right ventricle (RV) (LV: P = 0.006, RV: P < 0.0001) and the extent of RV dropout (P < 0.0001), while RDIR with 200% slice thickness significantly reduced RV signal heterogeneity (P = 0.001) and the extent of RV dropout (P = 0.0002). In patients, RDIR significantly reduced RV myocardial signal heterogeneity (0.31 vs. 0.43; P = 0.003) and the extent of RV dropout (24% vs. 46%; P = 0.0005). LV signal heterogeneity exhibited a trend towards improvement with RDIR (0.12 vs. 0.16; P = 0.06). Qualitative evaluation showed a significant improvement of LV and RV visualization in RDIR compared to DIR (LV: P = 0.04, RV: P = 0.0007) and a significantly improved overall image quality (P = 0.03). DATA CONCLUSION: RDIR TSE is less sensitive to through-plane motion, potentiating increased clinical utility for black-blood TSE. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:1498-1508.

Metabolic Coupling Determines the Activity: Comparison of 11ß-Hydroxysteroid Dehydrogenase 1 and Its Coupling between Liver Parenchymal Cells and Testicular Leydig Cells.

BACKGROUND: 11ß-hydroxysteroid dehydrogenase 1 (11ß-HSD1) interconverts active 11ß-hydroxyl glucocorticoids and inactive 11keto forms. However, its directionality is determined by availability of NADP+/NADPH. In liver cells, 11ß-HSD1 behaves as a primary reductase, while in Leydig cells it acts as a primary oxidase. However, the exact mechanism is not clear. The direction of 11ß-HSD1 has been proposed to be regulated by hexose-6-phosphate dehydrogenase (H6PDH), which catalyzes glucose-6-phosphate (G6P) to generate NADPH that drives 11ß-HSD1 towards reduction. METHODOLOGY: To examine the coupling between 11ß-HSD1 and H6PDH, we added G6P to rat and human liver and testis or Leydig cell microsomes, and 11ß-HSD1 activity was measured by radiometry. RESULTS AND CONCLUSIONS: G6P stimulated 11ß-HSD1 reductase activity in rat (3 fold) or human liver (1.5 fold), but not at all in testis. S3483, a G6P transporter inhibitor, reversed the G6P-mediated increases of 11ß-HSD1 reductase activity. We compared the extent to which 11ß-HSD1 in rat Leydig and liver cells might be coupled to H6PDH. In order to clarify the location of H6PDH within the testis, we used the Leydig cell toxicant ethane dimethanesulfonate (EDS) to selectively deplete Leydig cells. The depletion of Leydig cells eliminated Hsd11b1 (encoding 11ß-HSD1) expression but did not affect the expression of H6pd (encoding H6PDH) and Slc37a4 (encoding G6P transporter). H6pd mRNA level and H6PDH activity were barely detectable in purified rat Leydig cells. In conclusion, the availability of H6PDH determines the different direction of 11ß-HSD1 in liver and Leydig cells.

An alternative explanation of hypertension associated with 17α-hydroxylase deficiency syndrome.

The syndrome of 17α-hydroxylase deficiency is due to the inability to synthesize cortisol and is associated with enhanced secretion of both corticosterone and 11-deoxy-corticosterone (DOC). In humans, corticosterone and its 5α-Ring A-reduced metabolites are excreted via the bile into the intestine and transformed by anaerobic bacteria to 21-dehydroxylated products: 11ß-OH-progesterone or 11ß-OH-(allo)-5α-preganolones (potent inhibitors of 11ß-HSD2 and 11ß-HSD1 dehydrogenase). Neomycin blocks the formation of these steroid metabolites and can blunt the hypertension in rats induced by either ACTH or corticosterone. 3α,5α-Tetrahydro-corticosterone, 11ß-hydroxy-progesterone, and 3α,5α-tetrahydro-11ß-hydroxy-progesterone strongly inhibit 11ß-HSD2 and 11ß-HSD1 dehydrogenase activity; all these compounds are hypertensinogenic when infused in adrenally intact rats. Urine obtained from a patient with 17α-hydroxylase deficiency demonstrated markedly elevated levels of endogenous glycyrrhetinic acid-like factors (GALFs) that inhibit 11ß-HSD2 and 11ß-HSD1 dehydrogenase activity (>300 times greater, and >400 times greater, respectively, than those in normotensive controls). Thus, in addition to DOC, corticosterone and its 5α-pathway products as well as the 11-oxygenated progesterone derivatives may play a previously unrecognized role in the increased Na(+) retention and BP associated with patients with 17α-hydroxylase deficiency.

Role of 11ß-OH-C(19) and C(21) steroids in the coupling of 11ß-HSD1 and 17ß-HSD3 in regulation of testosterone biosynthesis in rat Leydig cells.

Here we describe further experiments to support our hypothesis that bidirectional 11ß-HSD1-dehydrogenase in Leydig cells is a NADP(H) regenerating system. In the absence of androstenedione (AD), substrate for 17ß-HSD3, incubation of Leydig cells with corticosterone (B) or several C(19)- and C(21)-11ß-OH-steroids, in the presence of [(3)H]-11-dehydro-corticosterone (A), stimulated 11ß-HSD1-reductase activity. However, in presence of 30 µM AD, testosterone (Teso) synthesis is stimulated from 4 to 197 picomole/25,000 cells/30 min and concomitantly inhibited 11ß-HSD1-reductase activity, due to competition for the common cofactor NADPH needed for both reactions. Testo production was further significantly increased (p<0.05) to 224-267 picomole/25,000 cells/30 min when 10 µM 11ß-OH-steroids (in addition to 30 µM AD) were also included. Similar results were obtained in experiments conducted with lower concentrations of AD (5 µM), and B or A (500 nM). Incubations of 0.3-6.0 µM of corticosterone (plus or minus 30 µM AD) were then performed to test the effectiveness of 17ß-HSD3 as a possible NADP(+) regenerating system. In the absence of AD, increasing amounts (3-44 pmol/25,000 cells/30 min) of 11-dehydro-corticosterone were produced with increasing concentrations of corticosterone in the medium. When 30 µM AD was included, the rate of 11-dehydro-corticosterone formation dramatically increased 1.3-5-fold producing 4-210 pmol/25,000 cells/30 min of 11-dehydro-corticosterone. We conclude that 11ß-HSD1 is enzymatically coupled to 17ß-HSD3, utilizing NADPH and NADP in intermeshed regeneration systems.

Clinical characteristics and four-year outcomes of patients in the Rhode Island Takotsubo Cardiomyopathy Registry.

The aim was to establish a registry of patients with a diagnosis of Takotsubo cardiomyopathy (TC) to help learn more about the characteristics, treatment strategies, and natural history of this disease. Data for patients with TC diagnosed from July 2004 to April 2008 at 2 major hospitals in Rhode Island were obtained. A data set was created that included baseline demographics and characteristics, hospital, course, and clinical outcomes. TC was diagnosed in 70 patients during the study period. Postmenopausal women comprised 95% of the cohort. Six patients presented with cardiogenic shock, 9 required intubation, 3 experienced sustained ventricular arrhythmias, and 1 patient died of cardiac causes. Average ejection fraction was 37% at cardiac catheterization. Troponin-I was increased in all except 1 patient. Follow-up echocardiography showed full recovery of wall motion abnormalities, with an average ejection fraction of 59%. Most patients were treated using standard cardiovascular medications for acute coronary syndrome, and 43% were discharged on warfarin therapy because of severe apical wall motion abnormalities. Univariate analysis suggested that long-term use of angiotensin-converting enzyme inhibitors before the onset of TC was protective against cardiogenic shock, sustained ventricular arrhythmia, and death. Consecutive cases grouped into different seasons showed a statistically significant spike in the occurrence of TC during the summer months. In conclusion, the acute phase of this condition may lead to critical illness and death, and use of an angiotensin-converting enzyme inhibitor may have a protective effect. Overall long-term prognosis and recovery of left ventricular function were excellent.

Interactions of mineralocorticoids and glucocorticoids in epithelial target tissues revisited.

The interplay between mineralocorticoids (MCs) and glucocorticoids (GCs) in sodium transporting epithelia is complex and only partially understood. In seminal papers published in the years soon after the discovery of aldosterone, various investigators experimentally observed that mineralocorticoid-induced renal sodium retention could only be reliably measured in adrenalectomized animals. Addition of endogenous GCs or their 11-dehydro metabolites blunted the antinatriuretic action of aldosterone and 11-dehydro-GCs decreased binding of aldosterone to mineralocorticoid receptors (MR). Under normal circumstances, endogenous GCs alone do not induce sodium transport in MC responsive epithelia yet these same GCs are able to activate MR and induce sodium transport if the enzyme 11beta-HSD2 is inhibited. Given the physiologic concentrations of both MCs and GCs, it is likely that the local epithelial cell exposure to GCs is great enough to allow GC binding to MR despite the presence of 11beta-HSD2. Thus other factors supplement the receptor selectivity role suggested for 11beta-HSD2. Why GCs bind to MR under one set of conditions and produce no effect and under different sets of conditions (11beta-HSD2 inhibition) elicit sodium transport remains a puzzle to be solved. What is clear is that a dual role for 11beta-HSD2 is emerging; first as the putative "guardian" over the MR reducing GC binding, and second as a source for 11-dehydro-GCs, which may serve as endogenously and locally produced "spironolactone-like substances", which may thus attenuate aldosterone-induced sodium transport.

Co-localization of glucocorticoid metabolizing and prostaglandin synthesizing enzymes in rat kidney and liver.

AIMS: The kidney metabolizes endogenous glucocorticoids using one of 2 isoforms of the enzyme 11ss-Hydroxysteroid Dehydrogenase (11ss-HSD). 11ss-HSD1 is located in the later portion of the proximal tubule and interstitial cells and 11ss-HSD2 is found in the mineralocorticoid sensitive collecting duct. Both renal isoforms appear to function as dehydrogenases, inactivating glucocorticoids. Since our laboratory has established that both renal cyclo-oxygenase-2 (COX-2) and 11ss-HSD1 co-localize in human kidney, we hypothesized that the two enzymes might functionally interact and influence each other's expression and/or activity. METHODS AND RESULTS: Using immuno-histochemistry staining with specific antibodies, both enzymes co-localize in later segments of proximal tubules in rat kidney and in rat hepatocytes. There was no co-localization with 11ss-HSD2 in the kidney. The co-localization was confirmed by Western blot and by immuno-precipitation in cultured rat proximal tubular cells (IRPTC). IRPTC incubated with corticosterone 1 microM or with corticosterone 10 nM plus the 11ss-HSD inhibitor carbenoxolone 1 microM demonstrated a decrease in the expression of COX-2 by Western blot at 24 h. When IRPTC were exposed to the COX-2 inhibitor, celecoxib, 11ss-HSD1 dehydrogenase activity was inhibited in a dose dependent manner with an IC50 of 1.4 microM. Celecoxib 2 microM had minimal effect on reductase activity in liver slices. CONCLUSIONS: Thus, COX-2 and 11ss-HSD1 co-localize in renal proximal tubules and in hepatocytes. In the kidney, each can influence the biological function of the other. The NSAID celecoxib may exert some of its anti-inflammatory effects on the kidney by locally prolonging the biologic half-life of endogenous glucocorticoids.

Rapid mechanisms of glucocorticoid signaling in the Leydig cell.

Stress-mediated elevations in circulating glucocorticoid levels lead to corresponding rapid declines in testosterone production by Leydig cells in the testis. In previous studies we have established that glucocorticoids act on Leydig cells directly, through the classic glucocorticoid receptor (GR), and that access to the GR is controlled prior to the GR by a metabolizing pathway mediated by the type 1 isoform of 11beta-hydroxysteroid dehydrogenase (11betaHSD1). This enzyme is bidirectional (with both oxidase and reductase activities) and in the rat testis is exclusively localized in Leydig cells where it is abundantly expressed and may catalyze the oxidative inactivation of glucocorticoids. The predominant reductase direction of 11betaHSD1 activity in liver cells is determined by an enzyme, hexose-6-phosphate dehydrogenase (H6PDH), on the luminal side of the smooth endoplasmic reticulum (SER). Generation of the pyridine nucleotide cofactor NADPH by H6PDH stimulates the reductase direction of 11betaHSD1 resulting in increased levels of active glucocorticoids in liver cells. Unlike liver cells, steroidogenic enzymes including 17beta-hydroxysteroid dehydrogenase 3 (17betaHSD3) forms the coupling with 11betaHSD1. Thus the physiological concentrations of androstenedione serve as a substrate for 17betaHSD3 utilizing NADPH to generate NADP+, which drives 11betaHSD1 in Leydig cells primarily as an oxidase; thus eliminating the adverse effects of glucocorticoids on testosterone production. At the same time 11betaHSD1 generates NADPH which promotes testosterone biosynthesis by stimulating 17betaHSD3 in a cooperative cycle. This enzymatic coupling constitutes a rapid mechanism for modulating glucocorticoid control of testosterone biosynthesis. Under stress conditions, glucocorticoids also have rapid actions to suppress cAMP formation thus to lower testosterone production.

Correlation of glycyrrhetinic acid-like factors (kidney 11beta-HSD2-GALFs) with urinary free cortisol and plasma renin activity in essential hypertension.

Previously we reported that urinary levels of glycyrrhetinic acid-like factors (11beta-HSD2-GALFs) were increased in a subset of patients with essential hypertension when maintained on a low-Na(+) diet. The present studies were undertaken to correlate changes in urinary GALF levels with urinary free cortisol (UFC) and plasma renin activity (PRA). The amounts of GALFs markedly increased from 7.38 +/- 0.80 to 14.58 +/- 1.94 (P < .0003) in the high/normal renin and from 5.60 +/- 0.77 to 8.39 +/- 1.08 (P < .045) in the low renin patients on a low-Na(+) diet compared with high-Na(+) diet with no effect in the normotensive controls (P < .668). The elevated GALF levels in high/normal renin hypertensives maintained on the low-Na(+) diet strongly correlated with the increased UFC levels and also with PRA; no such correlations were observed with either the normotensive controls or low renin hypertensives. In high/normal renin hypertensives, the elevated 11beta-HSD2-GALFs may have two major functions: increased Na(+) retention by the kidney by allowing cortisol to access the renal mineralocorticoid receptor and increased vascular reactivity by allowing cortisol to access the vascular mineralocorticoid receptor.

Endogenous selective inhibitors of 11beta-hydroxysteroid dehydrogenase isoforms 1 and 2 of adrenal origin.

In earlier studies [Latif, S.A., Sheff, M.F., Ribeiro, C.E., Morris, D.J., 1997. Selective inhibition of sheep kidney 11beta-hydroxysteroid-dehydrogenase isoform 2 activity by 5alpha-reduced (but not 5beta) derivatives of adrenocorticosteroids. Steroids 62, 230-237], only derivatives of steroid hormones possessing the 5alpha-Ring A-reduced configuration selectively inhibited 11beta-HSD2-dehydrogenase, whereas their 5beta-derivatives were inactive. This present study focuses on an expanded group of endogenous 11-oxygenated, 5alpha and 5beta-Ring A-reduced metabolites of adrenocorticosteroids, and progestogen and androgen steroid hormones. These substances were tested for their inhibitory properties against 11beta-HSD2, 11beta-HSD1-dehydrogenase and 11beta-HSD1 reductase. The present studies showed that the following compounds stand out as potent inhibitors. These are 5alpha-DH-corticosterone, 3alpha,5alpha-TH-corticosterone, 11beta-OH-progesterone, 11beta-OH-allopregnanolone, 11beta-OH-testosterone, and 11beta-OH-androstanediol, inhibitors of 11beta-HSD1-dehydrogenase; 3alpha,5alpha-TH-11-dehydro-corticosterone, 11-keto-progesterone, 11-keto-allopregnanolone, and 11-keto-3beta,5alpha-TH-testosterone, inhibitors of 11beta-HSD1 reductase; 3alpha,5alpha-TH-aldosterone, 5alpha-DH-corticosterone, 3alpha,5alpha-TH-corticosterone,11-dehydro-corticosterone, 3alpha,5alpha-TH-11-dehydro-corticosterone, 11beta-OH-progesterone, 11-keto-progesterone, 11beta-OH-allopregnanolone, 11-keto-allopregnanolone, 11beta-OH-testosterone, and 11-keto-testosterone, inhibitors of 11beta-HSD2. All of these substances have the potential to be derived from adrenally synthesized corticosteroids. Substances with similar structures to those described may help in the design of exogenous agents for the management of a variety of disease states involving 11beta-HSD isoenzymes.

Stimulation of testosterone production in rat Leydig cells by aldosterone is mineralocorticoid receptor mediated.

The testis is known to be a site of corticosterone action, and testosterone production in Leydig cells is directly inhibited by glucocorticoids. Glucocorticoids bind to both glucocorticoid receptors (GRs) and to mineralocorticoid receptors (MRs). In Leydig cells, selective mineralocorticoid binding could result from oxidative inactivation of glucocorticoid by type 1 and/or 2 11beta-hydroxysteroid dehydrogenase (11betaHSD), as both isoforms are expressed. However, it remains unclear whether Leydig cells express MRs and respond directly to mineralocorticoid action. Therefore, the aims of the present study were to ascertain: (1) whether MR mRNA, protein and receptor binding are present in Leydig cells; and (2) if the mineralocorticoid modulates testosterone production. The mRNA encoding MR, as well as protein, and binding activity were each observed in adult rat Leydig cells. MR-ligand binding specificity within isolated Leydig cells was evaluated further by measuring displacement of MR binding to aldosterone by corticosterone in the presence and absence of carbenoxolone, an inhibitor of 11betaHSD1 and 2 that decreases conversion to biologically inert 11-dehydrocorticosterone. Carbenoxolone inhibited 11betaHSD oxidative activity, and reduced corticosterone-binding by 50%. Mineralocorticoid effects on steroidogenesis were assessed in the presence of aldosterone (0.01-10 nM) with or without the MR antagonist, RU28318. Aldosterone induced dose-dependent increases in both basal and luteinizing hormone-stimulated testosterone production. RU28318 eliminated the increase, indicating that these effects of aldosterone were mediated by the MR. The effects of aldosterone and luteinizing hormone (0.1 ng/ml) on testosterone production were synergistic, suggesting that the two hormones increased steroidogenesis through separate pathways. We conclude that Leydig cells express MRs and that testosterone production is subject to regulation by aldosterone.

11{beta}-Hydroxysteroid dehydrogenase 2 in rat leydig cells: its role in blunting glucocorticoid action at physiological levels of substrate.

Corticosterone (CORT) suppresses Leydig cell steroidogenesis by inhibiting the expression of proteins involved in testosterone biosynthesis including steroidogenic acute regulatory protein and steroidogenic enzymes. In most cells, intracellular glucocorticoid levels are controlled by either or both of the two known isoforms of 11beta-hydroxysteroid dehydrogenase (11beta HSD): the nicotinamide adenine dinucleotide phosphate reduced-dependent low-affinity type I 11beta HSD (11beta HSD1) oxidoreductase and the nicotinamide adenine dinucleotide-dependent 11beta HSD2 high-affinity unidirectional oxidase. In Leydig cells, 11beta HSD1 alone may not be sufficient to prevent glucocorticoid-mediated suppression due to its low affinity for CORT at basal concentrations. The high-affinity unidirectional 11beta HSD2, if also present, may be critical for lowering intracellular CORT levels. In the present study, we showed that 11beta HSD2 is present in rat Leydig cells by PCR amplification, immunohistochemical staining, enzyme histochemistry, immunoprecipitation, and Western blotting. Real-time PCR showed a 6-fold enrichment of 11beta HSD2 mRNA in these cells, compared with whole testis and that the amount of 11beta HSD2 message was about 1000-fold lower, compared with 11beta HSD1. Diffuse immunofluorescent staining of 11beta HSD2 protein in the Leydig cell cytoplasm was consistent with its localization in the smooth endoplasm reticulum. 11beta HSD1 or 11beta HSD2 activities were selectively inhibited using antisense methodology: inhibition of 11beta HSD1 lowered reductase activity by 60% and oxidation by 25%, whereas inhibition of 11beta HSD2 alone suppressed oxidase activity by 50%. This shows that the high-affinity, low-capacity 11beta HSD2 isoform, present at only one thousandth the level of the low-affinity isoform may significantly affect the level of CORT. The inhibition of either 11beta HSD1 or 11beta HSD2 significantly lowered testosterone production in the presence of CORT. These data suggest that both types I and II 11beta HSD in Leydig cells play a protective role, opposing the adverse effects of excessive CORT on testosterone production.