Biotin-hydrazide derivatives for the development of steroid enzyme-linked immunoassays

Peptide-Catalyzed Highly Asymmetric Cross-Aldol Reaction of Aldehydes to Biomimetically Synthesize 1,4-Dicarbonyls

β-Turn tetrapeptides were demonstrated to catalyze asymmetric aldol reaction of α-branched aldehydes and α-carbonyl aldehydes, i.e. glyoxylates and α-ketoaldehydes, to biomimetically synthesize acyclic all-carbon quaternary center-bearing 1,4-dicarbonyls in high yield and excellent enantioselectivity under mild conditions. The spatially restricted environment of the tetrapeptide warrants high enantioselectivity and yield with broad substrates. Using this protocol, (R)-pantolactone, the key intermediate of vitamin B5, was readily accessed in a practical, efficient, and environmentally benign process from inexpensive starting materials.

Myeloid cells are capable of synthesizing aldosterone to exacerbate damage in muscular dystrophy

FDA-approved mineralocorticoid receptor (MR) antagonists are used to treat heart failure. We have recently demonstrated efficacy of MR antagonists for skeletal muscles in addition to heart in Duchenne muscular dystrophy mouse models and that mineralocorticoid receptors are present and functional in skeletal muscles. The goal of this study was to elucidate the underlying mechanisms of MR antagonist efficacy on dystrophic skeletal muscles. We demonstrate for the first time that infiltrating myeloid cells clustered in damaged areas of dystrophic skeletal muscles have the capacity to produce the natural ligand of MR, aldosterone, which in excess is known to exacerbate tissue damage. Aldosterone synthase protein levels are increased in leukocytes isolated from dystrophic muscles compared with controls and local aldosterone levels in dystrophic skeletal muscles are increased, despite normal circulating levels. All genes encoding enzymes in the pathway for aldosterone synthesis are expressed in muscle-derived leukocytes. 11β-HSD2, the enzyme that inactivates glucocorticoids to increase MR selectivity for aldosterone, is also increased in dystrophic muscle tissues. These results, together with the demonstrated preclinical efficacy of antagonists, suggest MR activation is in excess of physiological need and likely contributes to the pathology of muscular dystrophy. This study provides new mechanistic insight into the known contribution of myeloid cells to muscular dystrophy pathology. This first report of myeloid cells having the capacity to produce aldosterone may have implications for a wide variety of acute injuries and chronic diseases with inflammation where MR antagonists may be therapeutic.

18-hydroxycorticosterone, 18-hydroxycortisol, and 18-oxocortisol in the diagnosis of primary aldosteronism and its subtypes

CONTEXT

Diagnosis of primary aldosteronism (PA) is made by screening, confirmation testing, and subtype diagnosis (computed tomography scan and adrenal vein sampling). However, some tests are costly and unavailable in most hospitals.

OBJECTIVE

The aim of the study was to evaluate the role of serum 18-hydroxycorticosterone (s18OHB), urinary and serum 18-hydroxycortisol (u- and s18OHF), and urinary and serum 18-oxocortisol (u- and s18oxoF) in the diagnosis of PA and its subtypes, aldosterone-producing adenoma (APA) and bilateral adrenal hyperplasia (BAH).

PATIENTS

The study included 62 patients with low-renin essential hypertension (EH), 81 patients with PA (20 APA, 61 BAH), 24 patients with glucocorticoid-remediable aldosteronism, 16 patients with adrenal incidentaloma, and 30 normotensives.

INTERVENTION AND MAIN OUTCOME MEASURES

We measured s18OHB, s18OHF, and s18oxoF before and after saline load test (SLT) and 24-h u18OHF and u18oxoF.

RESULTS

PA patients displayed significantly higher levels of s18OHB, u18OHF, and u18oxoF compared to EH and normal subjects; APA patients displayed s18OHB, u18OHF, and u18oxoF levels significantly higher than BAH patients. Similar results were obtained for s18OHF and s18oxoF. SLT significantly reduced s18OHB, s18OHF, and s18oxoF in all groups, but steroid reduction was much less for APA patients compared to BAH and EH. The s18OHB/aldosterone ratio after SLT more than doubled in EH but remained unchanged in APA patients.

CONCLUSIONS

u18OHF, u18oxoF, and s18OHB measurements in patients with a positive aldosterone/plasma renin activity ratio correlate with confirmatory tests and adrenal vein sampling in PA patients. If verified, these steroid assays would refine the diagnostic workup for PA.

Physiologic roles of 11beta-hydroxysteroid dehydrogenase type 2 in kidney

We developed enzyme-linked immunosorbent assays to measure urinary free cortisone (E) and cortisol (F) and analyzed correlations between clinical measures reflecting mineralocorticoid action and 24-hour urinary excretion of E and F or their ratio, uE/F, which has been considered as the most sensitive index of renal 11beta-hydroxysteroid dehydrogenase type 2 activity. Two hundred nineteen healthy men were enrolled in this study. The uE/F ratio was 1.10 +/- 0.41 (mean +/- SD), and a strong linear correlation between uE and uF was observed in a double reciprocal plot. Urinary acid-labile aldosterone excretion had a negative correlation with 24-hour urinary Na excretion and Na/K ratio, but uE/F ratio had a weak positive correlation with the Na/K ratio and no significant correlation with 24-hour urinary Na excretion. In contrast, uE and uF had positive correlations with 24-hour urinary excretions of Na and K, raising the possibility of separate renal effects mediated by the glucocorticoid receptor. Furthermore, uE and uE/F ratio had strong negative correlations with urinary concentrations of Na and K. These results suggest that renal 11beta-hydroxysteroid dehydrogenase type 2 is an important regulatory factor of renal Na and K handlings independently of and/or complementary to the mineralocorticoid action of aldosterone.

Coexistence of different phenotypes in a family with glucocorticoid-remediable aldosteronism

In glucocorticoid-remediable aldosteronism (GRA), there is a large interfamily variation of phenotype. We report three subjects with GRA in a single family (parents, two brothers and two sisters), of whom only one (proband) displayed classical features of the mineralocorticoid excess. The proband was a man found to be hypertensive and hypokalaemic at the age of 24 years. Plasma renin activity was suppressed and plasma aldosterone was repeatedly elevated. Blood pressure and aldosterone levels normalized within 5 days of dexamethasone therapy. The presence of a chimaeric CYP11B1/CYP11B2 gene was demonstrated by long-PCR and Southern blotting (crossover site at the end of intron 3) in the proband, in the younger sister (sibling 1) and in the father. In these patients, sequencing of the chimaeric portion of CYP11B1 did not reveal any mutation, while sequencing of the chimaeric portion of CYP11B2 showed a V386A polymorphism in exon 7, known to cause only a minimal impairment of enzymatic activity. Sibling 1 was normotensive, normokalaemic and had normal PRA and aldosterone. The father had normal blood pressure and potassium, low-normal PRA and normal aldosterone. All three subjects had elevated levels of urinary 18-hydroxycortisol and 18-oxocortisol. Baseline 11-deoxycorticosterone (DOC), corticosterone (B) and aldosterone were high in the proband and normal in the father and sibling 1; 11-deoxycortisol (S) and cortisol (F) were normal. ACTH induced a normal increase of B, DOC, S and F, and an excessive aldosterone increase in all three patients. Abnormalities in the chimaeric portions of CYB11B1 or CYP11B2 genes did not account for the phenotypic disparity of the different members in a single GRA family. Altered regulation of the chimaeric gene may be responsible for differences in its activity.

Origin of aldosterone in the rat heart

Aldosterone has been demonstrated in the perfusate of the ex situ rat heart and heart homogenates; however, the origin of aldosterone in the heart is controversial, with some reporting a primary role for extraadrenal synthesis within the heart, and others finding that all of the aldosterone in the heart is sequestered from the circulation. In an attempt to resolve this controversy, we measured the aldosterone and corticosterone contents of plasma and hearts of rats on a normal salt (NS), low salt (LS), or high salt (HS) diet, adrenalectomized (ADX+HS), and ADX with aldosterone replacement or deoxycorticosterone excess (ADX+HS+DOC) before tissue harvest. The sodium content of the diet had no significant effect on corticosterone levels in the plasma or heart. LS significantly increased, whereas HS decreased the aldosterone content of plasma and heart compared with NS. Corticosterone levels in both plasma and heart and aldosterone levels in plasma of ADX-HS rats were undetectable in most individuals and were extremely low in very few. Although plasma aldosterone was undetectable, aldosterone was measurable in 30% of the hearts of 84 ADX+HS rats, albeit at low levels. The aldosterone and corticosterone contents of the hearts of ADX+HS+DOC were similar to those of ADX+HS, indicating that aldosterone synthase and 11beta-hydroxylase, not substrate, are the limiting factors for extraadrenal synthesis of corticosteroids in the heart. In conclusion, we found that the level of aldosterone content in the healthy rat heart in vivo is significantly lower than that reported elsewhere and reflects plasma levels in intact rats.

Plasma cortisol and cortisone concentrations in normal subjects and patients with adrenocortical disorders

Two isozymes of the 11beta-hydroxysteroid dehydrogenase (11-HSD) are responsible for the interconversion of cortisol (F) and cortisone (E). The type 1 isozyme, 11-HSD1, acts mainly as a reductase in vivo, activating E to F, whereas the type 2, 11-HSD2, acts as a dehydrogenase, inactivating F to E. 11-HSD1 is the most abundant in the liver and 11-HSD2 in the kidney. In this study, we attempted to determine which isozyme and organs primarily contribute to equilibrium of plasma F and E concentrations in the peripheral circulation and to clarify differences in 11-HSD activities among adrenocortical disorders. Upon selective catheterizations for adrenocortical and renovascular disorders, plasma F and E concentrations in the femoral vein were closer to those in the renal vein than those in the hepatic vein. Values for mean plasma F/E ratios in the peripheral vein were in-between those of the adrenal and renal veins. A double reciprocal plot between peripheral plasma F and E concentrations in patients with various adrenocortical tumors was almost identical to that in normal subjects. Mean plasma F/E ratio in peripheral blood was higher in patients with Cushing's syndrome and was lower in patients with primary aldosteronism and nonfunctioning adrenocortical adenoma than that in normal subjects. These results suggest that renal 11-HSD2 is a main factor controlling the equilibrium of plasma F and E concentrations in the periphery and that cortisol and aldosterone excess do not change the equilibrium of plasma F and E concentrations in the peripheral circulation, but may alter expression of 11-HSD2. Alternation of 11-HSD2 activities as well as corticosteroid levels may be important in the pathophysiology of adrenocortical disorders.

Regulation of 11 beta-hydroxysteroid dehydrogenase enzymes in the rat kidney by estradiol

The 11beta-hydroxysteroid dehydrogenase (11betaHSD) type 1 (11betaHSD1) enzyme is an NADP+-dependent oxidoreductase, usually reductase, of major glucocorticoids. The NAD+-dependent type 2 (11betaHSD2) enzyme is an oxidase that inactivates cortisol and corticosterone, conferring extrinsic specificity of the mineralocorticoid receptor for aldosterone. We reported that addition of a reducing agent to renal homogenates results in the monomerization of 11betaHSD2 dimers and a significant increase in NAD+-dependent corticosterone conversion. Estrogenic effects on expression, dimerization, and activity of the kidney 11betaHSD1 and -2 enzymes are described herein. Renal 11betaHSD1 mRNA and protein expressions were decreased to very low levels by estradiol (E2) treatment of both intact and castrated male rats; testosterone had no effect. NADP+-dependent enzymatic activity of renal homogenates from E2-treated rats measured under nonreducing conditions was less than that of homogenates from intact animals. Addition of 10 mM DTT to aliquots from these same homogenates abrogated the difference in NADP+-dependent activity between E2-treated and control rats. In contrast, 11betaHSD2 mRNA and protein expressions were significantly increased by E2 treatment. There was a marked increase in the number of juxtamedullary proximal tubules stained by the antibody against 11betaHSD2 after the administration of E2. Notwithstanding, neither the total corticosterone and 11-dehydrocorticosterone excreted in the urine nor their ratio differed between E2- and vehicle-treated rats. NAD+-dependent enzymatic activity in the absence or presence of a reducing agent demonstrated that the increase in 11betaHSD2 protein was not associated with an increase in in vitro activity unless the dimers were reduced to monomers.

Plasma 11beta-hydroxy-4-androstene-3,17-dione: comparison of a time-resolved fluoroimmunoassay using a biotinylated tracer with a radioimmunoassay using a tritiated tracer

The plasma concentration of 11beta-hydroxy-4-androstene-3,17-dione (11beta) is very high in 21-hydroxylase deficiency, Cushing's syndrome, and hyperandrogenism of adrenal origin, and very low in congenital 11-hydroxylase deficiency and adrenal insufficiency. Thus, when plasma 4-androstenedione is elevated, it is useful to measure the plasma 11beta level in order to determine the adrenal or ovarian origin of the hyperandrogenism. To eliminate disadvantages related to the 11beta radioimmunoassay (RIA), which uses a tritiated tracer, as well as the high cost associated with scintillation proximity assay (SPA), we developed a non-isotopic 11beta assay that utilizes an 11beta-biotin conjugate synthesized in our laboratory to measure time-resolved fluorescence after addition of streptavidin-europium to microtitration wells. The analytical qualities of this assay are very similar to those of the radioimmunoassay using a tritiated tracer, and an extraction step followed by celite chromatography (which separates 11beta from interfering plasma steroids) prior to a final radioimmuno-competition step. The correlation coefficient between 11beta levels measured by time-resolved plasma 11beta fluoroimmunoassay (TR-FIA) and RIA was 0.965.Finally, the TR-FIA technique was more sensitive and of greater precision than the RIA method.

Development of a new sensitive and specific time-resolved fluoroimmunoassay (TR-FIA) of chlormadinone acetate in the serum of treated menopausal women

We describe the development of a serum chlormadinone acetate (CMA) time-resolved fluoroimmunoassay (TR-FIA). We prepared haptens (3-CMO-chlormadinone acetate and 6-chloropregna-4,6-dien-17,20-diol-3-one-20-hemisuccinate), biotinylated tracers (3(biotinylaminopropylamido) 3-CMO-chlormadinone acetate and 3-(6-chloropregna-4,6-dien-17,20-diol-3-one-20-hemisuccinylamino)1-biotinylaminopropane), and immunogens necessary for eliciting two antibodies (anti-chlormadinone acetate 3-CMO/BSA and anti-chlormadinone 20-hemisuccinate/BSA). The specificity of the assay was rigorously studied to eliminate possible interference by polar metabolites of CMA, particularly 17 alpha-acetoxy-6-chloro-3beta-hydroxypregna-4,6-diene-20-one (3beta-hydroxy metabolite), employing an easy-to-use ethylene glycol chromatographic step prior to immunoassay, so as to separate the polar metabolites, in particular the 3beta-hydroxy-CMA metabolite, from the intact CMA. The choice of the anti-CMA antibody was guided by the high assay sensitivity obtained with the anti-CMA 3-CMO/BSA antibody. The detection limit was 51pg/ml. Interassay reproducibility CVs were between 2.6 and 4.5%. This TR-FIA thus appeared to be a sensitive, specific, precise, and consequently well-suited method for measurement of serum CMA during a pharmacokinetic study in women.

A time-resolved fluoroimmunoassay for 18-oxocortisol and 18-hydroxycortisol. Development of a monoclonal antibody to 18-oxocortisol

Patients with primary aldosteronism and with glucocorticoid-suppressible aldosteronism excrete in the urine excessive amounts of the hybrid steroids 18-hydroxycortisol and 18-oxocortisol. The measurement of these steroids aids in the differential diagnosis of various adrenal disorders. We have produced mouse monoclonal antibodies against 18-oxocortisol and polyclonal antibodies against 18-hydroxycortisol and describe a time-resolved fluoroimmunoassay (TR-FIA) technique for the measurement of these steroids in the urine. We have also compared this assay with an ELISA technique for these compounds. We also describe the preparation of in-house Eu(III)-labeled avidin and an enhancement solution and compared to a commercially available Eu(III)-labeled streptavidin and enhancement solutions. The monoclonal antibodies against 18-oxocortisol are sensitive and have a high level of specificity. The TR-FIA technique using in-house prepared reagents or commercial ones were indistinguishable from each other, but at a significant saving. The TR-FIA technique was more sensitive and had a greater precision than the ELISA technique for both steroids.

Genetic study of patients with dexamethasone-suppressible aldosteronism without the chimeric CYP11B1/CYP11B2 gene

Glucocorticoid-remediable aldosteronism is an inherited disorder caused by a chimeric gene duplication between the CYP11B1 (11beta-hydroxylase) and CYP11B2 (aldosterone synthase) genes. The disorder is characterized by hyperaldosteronism and high levels of 18-hydroxycortisol and 18-oxocortisol, which are under ACTH control. The diagnosis of glucocorticoid-remediable aldosteronism had been traditionally made using the dexamethasone suppression test; however, recent studies have shown that several patients with primary aldosteronism and a positive dexamethasone suppression test do not have the chimeric CYP11B1/CYP11B2 gene. The aim of this work was to evaluate whether other genetic alterations exist in CYP11B genes (gene conversion in the coding region of CYP11B1 or in the promoter of CYP11B2) that could explain a positive dexamethasone suppression test and to determine another genetic cause of glucocorticoid-remediable aldosteronism. We also evaluated the role of 18-hydroxycortisol as a specific biochemical marker of glucocorticoid-remediable aldosteronism. We studied eight patients with idiopathic hyperaldosteronism, a positive dexamethasone suppression test, and a negative genetic test for the chimeric gene. In all patients we amplified the CYP11B1 gene by PCR and sequenced exons 3-9 of CYP11B1 and a specific region (-138 to -284) of CYP11B2 promoter. We also measured the levels of 18-hydroxycortisol, and we compared the results with those found in four subjects with the chimeric gene. None of eight cases showed abnormalities in exons 3-9 of CYP11B1, disproving a gene conversion phenomenon. In all patients a fragment of 393 bp corresponding to a specific region of the promoter of CYP11B2 gene was amplified. The sequence of the fragment did not differ from that of the wild-type promoter of the CYP11B2 gene. The 18-hydroxycortisol levels in the eight idiopathic hyperaldosteronism patients and four controls with chimeric gene were 3.9 +/- 2.3 and 21.9 +/- 3.5 nmol/liter, respectively (P < 0.01). In summary, we did not find other genetic alterations or high levels of 18-hydroxycortisol that could explain a positive dexamethasone suppression test in idiopathic hyperaldosteronism. We suggest that the dexamethasone suppression test could lead to an incorrect diagnosis of glucocorticoid-remediable aldosteronism.

Serum 18-hydroxycortisol in primary aldosteronism, hypertension, and normotensives

This study reports the determination of plasma 18-hydroxycortisol (18-OHF) using a new and easy enzyme-linked immunosorbent assay (ELISA) method in primary aldosteronism and compares the values found in essential hypertensives and normotensive controls. In primary aldosteronism, we evaluated usefulness of plasma 18-OHF determination and the dexamethasone suppression test in the diagnosis of glucocorticoid-remediable aldosteronism using the genetic test as the gold standard. We studied 31 primary aldosteronism patients, 101 essential hypertensives, and 102 healthy normotensive controls. The plasma 18-OHF was measured using a biotin-avidin enzyme-linked assay by a new and purified polyclonal antibody. The 18-OHF value in primary aldosteronism was 6.3+/-8.05 nmol/L; this value is significantly higher than the value found in essential hypertensives and normotensive controls (2.81+/-1.42 and 2.70+/-1.41 nmol/L, respectively; P<0.0005). In primary aldosteronism, 4 of 31 patients had 18-OHF levels that were 10 times higher than the normal upper limit (2.983 nmol/L). The dexamethasone suppression test in primary aldosteronism patients was positive (serum aldosterone <4 ng/dL) in 13 of 31 cases. A chimeric CYP11B1/CYP11B2 gene was demonstrated in 4 primary aldosteronism patients, corresponding to the same cases that had higher level of 18-OHF. In conclusion, plasma 18-OHF determination by this ELISA method is reliable for detecting glucocorticoid-remediable aldosteronism, and it does so better than the dexamethasone suppression test.

Plasma 17-OH pregnenolone: comparison of a time-resolved fluoroimmunoassay using a new tracer 17-OH pregnenolone-3-oxyacetyl-biotine with a radioimmunoassay using 125I 17-OH pregnenolone-3-hemisuccinate-histamine

In this article we described, for the first time to our knowledge, the development of a new non isotopic immunoassay (time resolved-fluoroimmunoassay) for determining 17alpha-hydroxypregnenolone levels in plasma or serum. This steroid is indeed the most relevant steroid for the diagnosis of 3beta-hydroxysteroid dehydrogenase deficiency. For the hapten tracer, we synthesized a biotin-oxyacetyl 17-hydroxypregnenolone conjugate. A specific polyclonal rabbit anti-17-hydroxypregnenolone was indirectly bound via an immobilized sheep anti-rabbit antibody on microtiter plate wells. The amount of biotin-17-hydroxypregnenolone conjugate bound was then measured by adding Streptavidin-Europium, and the Europium fluorescence was quantified by Time Resolved -Fluorescence (TR-FIA, Delfia System). The plasma 17-hydroxypregnenolone levels of this non isotopic assay were comparatively measured with a radioimmunoassay previously published and using the same anti 17-hydroxypregnenolone antibody. In both cases, the assays were performed after a extraction step and a chromatographic step. The sensitivity of this 17-hydroxypregnenolone time resolved-fluoroimmunoassay was higher than that of 17-hydroxypregnenolone radioimmunoassay. The compared results of plasma 17-hydroxypregnenolone, performed with these two methods were not significantly different. A practical advantage is the stability of the biotine tracer, comparatively to the radioactive 125I 17-hydroxypregnenolone tracer which requires a new labeling every two months.

Development of a plasma 17alpha-hydroxyprogesterone time resolved-fluorescence immunoassay involving a new biotinylated tracer

A biotinylated 17alpha-hydroxyprogesterone probe (3) was prepared from 17alpha-hydroxyprogesterone-3-carboxymethyloxime and conjugate obtained by acylation of biotinylaminopropylammonium trifluroacetate. This new tracer was used in the development of a 17alpha-hydroxyprogesterone time-resolved fluoroimmunoassay using streptavidin-europium. The new method was compared to a long-standing radioimmunoassay method and found to be more sensitive and economical.

Plasma 21-deoxycortisol: comparison of a time-resolved fluoroimmunoassay using a biotinylated tracer with a radioimmunossay using (125)iodine

Plasma 21-deoxycortisol (21DF) is an excellent marker of 21-hydroxylase deficiency. Currently, it is the only marker able to detect heterozygous carriers with 21-hydroxylase deficiency after ACTH stimulation. We have already developed radioimmunoassays for 21DF using first tritiated, then 125I-21DF which had a ten-fold higher sensitivity. However, because the lifespan of 125I-21DF is short, the tracer needs to be reprepared every two months and this multiplies the risk of contamination by radioactive 125I vapours. We therefore developed a non-isotopic 21DF assay that uses a 21DF-biotin conjugate with a original bridge, a diaminopropyl arm, linking the steroid to biotin. The 21DF-biotin conjugate was measured by time-resolved fluorescence after adding streptavidin-europium to the microtitration wells. The analytical qualities of this assay were very similar to those of the radioimmunoassay using 125I-21DF as tracer. The results obtained by the two methods, in either normal subjects or patients with 21-hydroxylase deficiency, were virtually the same.

Levels of mineralocorticoids in whites and blacks

Blacks appear, on average, to retain more Na than whites. A higher production rate of mineralocorticoids could explain the greater Na retention in blacks. Although production of aldosterone has been shown to be lower in blacks, the level of another mineralocorticoid may be increased. Plasma levels of deoxycorticosterone and cortisol were measured in young whites (n=23; age=16.4+/-3.1[SD] years) and young blacks (n=25; age=13.8+/-1.3 years). Blacks had lower plasma levels of renin activity and aldosterone and lower urinary aldosterone excretion rates; thus, they appeared to be representative of blacks that retain additional Na. Plasma deoxycorticosterone levels were lower in blacks than in whites both at baseline (247+/-161 versus 381+/-270 pmol/L, P=0.048) and after stimulation with adrenocorticotropic hormone (822+/-294 versus 1127+/-628 pmol/L at 30 minutes, P=0.047; 925+/-366 versus 1440+/-834 pmol/L at 60 minutes, P=0.013). Cortisol levels were also lower in blacks at baseline (P=0.014) but were not significantly different from levels in whites after stimulation with adrenocorticotropic hormone. In a larger cohort of 407 whites (age=12.0+/-2.9 years) and 247 blacks (age=12.9+/-3.1 years), 18-hydroxycortisol excretion rates were also lower in blacks (P=0. 021). In conclusion, increased Na retention in blacks does not appear to be secondary to increased production of either aldosterone, deoxycorticosterone, cortisol, or 18-hydroxycortisol. A primary renal mechanism may mediate the increase in Na reabsorption in blacks.

Impaired neuroendocrine response mediates refractoriness to cardiopulmonary resuscitation in spinal anesthesia

OBJECTIVE

To determine the extent of neurogenic control on adrenal secretion in a canine model of high spinal anesthesia and cardiac arrest.

DESIGN

Randomized, controlled, acute intensive study.

SETTING

University intensive care laboratory.

SUBJECTS

Nineteen healthy, anesthetized, mongrel dogs.

INTERVENTIONS

Cardiac arrest was induced in 11 spinally anesthetized dogs and 8 sham-control animals; cardiopulmonary resuscitation (CPR) was started 60 secs later. Epinephrine was injected at 4 mins and every 2 mins thereafter. Arterial blood samples were obtained before anesthesia, before arrest, and after 1, 3, 5, 7, 9, and 11 mins of CPR.

MEASUREMENTS AND MAIN RESULTS

At 1 and 3 mins after cardiac arrest, the control group exhibited significant increases of epinephrine and norepinephrine concentrations (p < .05) that were absent in the spinal anesthesia group. Plasma renin increased in both groups whereas aldosterone and cortisol remained unchanged.

CONCLUSIONS

Spinal anesthesia abolishes the catecholamine release that follows cardiac arrest, while a previously postulated direct adrenal effect of hypoxia stimulating catecholamine release was not confirmed in these experiments. Since epinephrine treatment restores coronary perfusion pressure (CPP) during CPR, we conclude that catecholamine deficiency is the most likely mechanism for inadequate CPP during CPR conducted in the presence of spinal anesthesia.

Regulation of the 11 beta-hydroxysteroid dehydrogenase in the rat adrenal. Decrease enzymatic activity induced by ACTH

Patients with ectopic ACTH syndrome often develop hypertension and hypokalemic alkalosis with an abnormal increase in the ratio of plasma cortisol to cortisone, indicating that 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) activity is inhibited. Inhibition of 11 beta HSD allows access of cortisol or corticosterone to the mineralocorticoid receptor where it act as a mineralocorticoid. Two isozymes, 11 beta HSD-1 and 11 beta HSD-2, have been cloned and characterized. The rat adrenal expresses the mRNAs for 11 beta HSD-2 and, in lesser amounts, 11 beta HSD-1. We investigated the effect of ACTH on the 11 11 beta HSD-2 activity in the rat adrenal. Rat adrenal cells zone fasciculata (ZF) were dispersed and incubated separately with increasing concentrations of ACTH for 90 min, and secretion of corticosterone (B) and 11-dehydrocorticosterone (A) in the media was measured by enzyme-linked immunoabsorbent assays (ELISA). The conversion of [3H]B to [3H]A in the presence of 0.5 mM NAD+ was evaluated in microsomes prepared from dispersed cells preincubated for 30 min with cyanoketone and metyrapone followed by incubation for 30 min with the same inhibitors, with and without 10 nM ACTH. The dispersed cells of the ZF produced significant amounts of A which increased with ACTH. The basal B/A ratio was 0.97 +/- 0.05. ACTH caused a concentration-dependent increase in the ratio of B/A with a maximum ratio of 9.58 +/- 0.20. ACTH also inhibited the conversion of [3H]B to [3H]A in microsomes in which endogenous B production was inhibited by cyanoketone and metyrapone. ACTH did not change the K(m) for B conversion, but the Vmax was reduced significantly (1.73 +/- 0.43 pmol/min. mg protein), indicating that ACTH suppressed the 11 beta HSD-2 in a noncompetitive fashion. Dibutyryl cyclic AMP (dcAMP) also produced a concentration-dependent increase in the B/A ratio, but various concentrations of calcium did not affect the enzyme activity. In summary, adrenal cells treated with ACTH results in a significant increase in the ratio of B/A in the ZF owing a noncompetitive inhibition of the 11 beta HSD-2 via the ACTH receptor.

Glucocorticoid-suppressible hyperaldosteronism and adrenal tumors occurring in a single French pedigree

Glucocorticoid-suppressible hyperaldosteronism is a dominantly inherited form of hypertension believed to be caused by the presence of a hybrid CYP11B1/CYP11B2 gene which has arisen from an unequal crossing over between the two CYP11B genes in a previous meiosis. We have studied a French pedigree with seven affected individuals in which two affected individuals also have adrenal tumors and two others have micronodular adrenal hyperplasia. One of the adrenal tumors and the surrounding adrenal tissue has been removed, giving a rare opportunity to study the regulation and action of the hybrid gene causing the disease. The hybrid CYP11B gene was demonstrated to be expressed at higher levels than either CYP11B1 or CYP11B2 in the cortex of the adrenal by RT-PCR and Northern blot analysis. In situ hybridization showed that both CYP11B1 and the hybrid gene were expressed in all three zones of the cortex. In cell culture experiments hybrid gene expression was stimulated by ACTH leading to increased production of aldosterone and the hybrid steroids characteristic of glucocorticoid-suppressible hyperaldosteronism. The genetic basis of the adrenal pathologies in this family is not known but may be related to the duplication causing the hyperaldosteronism.

Application of enzymeimmunoassay to measure oestrone sulphate concentrations in cow's milk during pregnancy

The characteristics of antigen- and antibody-coated enzymeimmunoassay (EIA) formats to measure oestrone sulphate (OS) were studied using a murine monoclonal antibody as the primary antibody. In an antigen-coated format the most sensitive EIA (9 fmol/well) was achieved using 6-ketoestrone-6-O-carboxymethyloxime (OCMO) coupled to bovine serum albumin (BSA), as the coating antigen, and horseradish peroxidase (HRP), as the enzyme label. In an antibody-coated format, comparable sensitivity could be achieved using HRP conjugated to either OCMO, oestrone-3-glucuronide (OG) or oestrone-3-hemisuccinate (OHS) as the steroid 'tracer'. In both the antigen- and antibody-coated formats replacing HRP with alkaline phosphatase (AP) markedly aggravated the assay sensitivity. The antigen-coated EIA format was used to measure OS concentrations in cow's milk directly without an initial defatting step, and a progressive increase in OS concentrations in milk as pregnancy progressed was observed. Median OS concentrations rose from 1.1 nmol/l at days 70-99 of pregnancy (n = 44) to 3.2 nmol/l at days 140-160 (n = 92). Oestrone sulphate concentrations in milk from non-pregnant cows (n = 51) ranged from non-detectable to 1.3 nmol/l with a median value of 0.4 nmol/l. Only 5% of cows 120 or more days pregnant had milk OS concentrations within the range of values found in milk from non-pregnant cows. Accurate discrimination of non-pregnant and pregnant cows can thus be achieved on the basis of OS concentrations in milk samples taken at least 120 days after mating/insemination. This EIA for OS may have a role in the dairy industry as an alternative non-invasive means of determining pregnancy status in cows.

18-Ethynyl-deoxycorticosterone inhibition of steroid production is different in freshly isolated compared to cultured calf zona glomerulosa cells

The inhibiting effects of 18-ethynyl-deoxycorticosterone (18-E-DOC) as a mechanism-based inhibitor on the late-steps of the aldosterone biosynthetic pathway were examined in calf adrenal zona glomerulosa cells in primary culture and in freshly isolated calf zona glomerulosa cells. 18-E-DOC inhibited the stimulated secretion of aldosterone and 18-hydroxycorticosterone in a similar dose-response and time fashion. No significant differences were found between the inhibition in cultured and freshly isolated cells (Ki of 0.25 vs 0.26 microM) Corticosterone secretion stimulated by ACTH or angiotensin II was also cultured in freshly isolated zona glomerulosa and fasciculata cells, but was not inhibited in cultured calf adrenal cells. Cortisol secretion stimulated by ACTH was not inhibited by 18-E-DOC in cultured zona fasciculata adrenal cells, but was inhibited in freshly isolated zona fasciculata cells with a Ki of 48 microM. The secretion of 18-hydroxyDOC or 19-hydroxyDOC stimulated by ACTH was not inhibited by 18-E-DOC. The bovine adrenal has been reported to have cytochrome P-450 11 beta-hydroxylases that can perform the various hydroxylations required for the synthesis of cortisol and aldosterone in the different areas of the adrenal. In other species a distinct 11 beta-hydroxylase which participates in the biosynthesis of aldosterone and is located in the zona glomerulosa has been described. These studies with the mechanism-based inhibitor, 18-E-DOC, suggest that the bovine adrenal functions in a manner very similar to that of other species and raises the possibility that a distinct 11 beta-hydroxylase with aldosterone synthase activity might be present, but has not been cloned as yet.

Regulation of 18-oxocortisol and 18-hydroxycortisol by the renin-angiotensin system and ACTH in man

Based on urinary excretion studies the secretion of the cortisol derivatives, 18-oxocortisol and 18-hydroxycortisol are believed to be regulated by ACTH and to a lesser degree by the renin-angiotensin system. Plasma concentrations of 18-oxocortisol and 18-hydroxycortisol were measured during the simultaneous activation of the renin-angiotensin system and inhibition of ACTH secretion. Five healthy male subjects consuming a sodium diet ad libitum were studied. Blood was drawn at 0800 h after 1 h in the supine position. In the first set of experiments, the subjects remained in the supine position from 0800 to 1000 h with or without the oral administration of 2 mg dexamethasone at 0800 h. In the second set of experiments the subjects were placed in the upright position after drawing the 0800 h sample. The subjects were studied with and without dexamethasone administered at 0800 h. Blood was drawn again at 1000 h. Plasma levels of 18-oxocortisol, 18-hydroxycortisol, ACTH, plasma renin activity (PRA), cortisol, aldosterone and 18-hydroxycorticosterone were measured by radioimmunoassay. None of these parameters changed during the 2 h in the supine position. 18-Oxocortisol, 18-hydroxycortisol, aldosterone, 18-hydroxycorticosterone and PRA increased, but ACTH and cortisol did not change when the subjects were placed in the upright position. After dexamethasone administration, 18-oxocortisol, 18-hydroxycortisol, cortisol, aldosterone and 18-hydroxycorticosterone decreased in the supine position and no increase occurred in 18-oxocortisol, 18-hydroxycortisol and 18-hydroxycorticosterone in the upright position. PRA and aldosterone increased and ACTH and cortisol decreased in these subjects. 18-Oxocortisol and 18-hydroxycortisol were more dependent on ACTH regulation and less on the renin-angiotensin system than aldosterone.