The tissue effects of mineralocorticoids

Influence of long-term, high-dose dexamethasone administration on proliferation and apoptosis in porcine hepatocytes

The aim of this study was to examine the influence of long-term, high-dose dexamethasone administration on the liver, with particular emphasis on hepatocyte proliferation and apoptosis, using a swine model. The study included 48 large, female Polish breed pigs aged 3months (weighing ca. 30kg) divided into groups I (control; n=24) and II (dexamethasone; n=24) that receiving intra-muscular injections of monosodium phosphate dexamethasone for 29days. The pigs were euthanized on days subsequent to the experiment. Immediately after the euthanasia, the pig livers were sampled, fixed, and processed routinely for histopathology, histochemistry, and immunohistochemistry (for proliferating cell nuclear antigen, Bcl-2, and caspase-3). Apoptosis was visualized by terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL). Dexamethasone administration gradually caused hepatocyte glycogen degeneration and finally lipid degeneration, accompanied by sinusoid and central vein dilatation and nuclear chromatin condensation. The proliferating cell nuclear antigen index, mean number of argyrophilic nucleolar organizer regions and proliferation index of argyrophilic nucleolar organizer regions were lower, while Bcl-2 expression was higher in group II compared with group I. The results from this study suggest that safe high-dose dexamethasone administration time is difficult to establish. Long-term, high-dose dexamethasone administration can cause pronounced morphological changes in hepatocytes by diminishing their transcriptional and proliferation activity but also protects them from apoptosis by potentially affecting Bcl-2 expression.

Evaluation of polyherbal formulation (SJT-HT-03) for antihypertensive activity in albino rats

BACKGROUND

Hypertension is an incurable pathological condition and lifelong therapy is required. Long term use of conventional synthetic anti-hypertensive drugs is associated with a spectrum of toxic effects. However, therapeutic interventions using herbal drugs for hypertension have gained considerable attention worldwide.

AIM

To evaluate the anti-hypertensive activity of polyherbal formulation (SJT-HT-03).

MATERIALS AND METHODS

The polyherbal formulation (SJT-HT-03) comprises of leaves of Aegle marmelos L., fruits of Benincasa hispida Thunb., Garcinia indica Thouars, and flowers of Musa paradiasica L., Rosa indica L., Hibiscus rosa sinensis L. Selected plants as mentioned above were collected, dried and extracted with different solvents. Formulation SJT-HT-03 (250 mg/kg, p.o.), was evaluated using two kidney one clip (2K1C) model and deoxycorticosterone acetate (DOCA)-salt-induced hypertension model using the enalapril (10 mg/kg, p.o.) and hydrochlorothiazide (5 mg/kg, p.o.) as a reference standard drug in respective models.

RESULTS

SJT-HT-03 significantly reduced (P < 0.001, one-way analysis of variance followed by Turkey's multiple comparison tests) systolic as well as diastolic blood pressure (BP) in 2K1C and DOCA-salt model. Further, SJT-HT-03 has shown a significant reduction (P < 0.01) in angiotensin converting enzyme (ACE) activity in serum, clipped kidney as well as in lungs in 2K1C model, whereas significant reduction (P < 0.05) in serum Na(+) and increase in serum K(+) level in DOCA model.

CONCLUSION

Polyherbal formulation SJT-HT-03 possess significant anti-hypertensive activity by producing direct depressant effect on heart, inhibition of ACE, aldosterone antagonistic as well as diuretic effect and thereby act on multiple targets to achieve optimal effect.

Increased expression of the mineralocorticoid receptor in the brain of spontaneously hypertensive rats

The mineralocorticoid receptor (MR) has been considered as both neuroprotective and damaging to the function of the central nervous system. MR may be also involved in central regulation of blood pressure. In the present study, we compared the expression of MR and the glucocorticoid receptor (GR) in the hippocampus and hypothalamus of 16-week-old spontaneously hypertensive rats (SHR) and normotensive control Wistar Kyoto (WKY) rats. In the hippocampus, MR expression was studied by in situ hybridization (ISH), quantitative polymerase chain reaction (PCR) and immunohistochemistry, whereas GR expression was analysed using the latter two procedures. Hypertensive animals showed an increased expression of MR mRNA in the whole hippocampus according to qPCR data and also in CA3 by ISH. Immunocytochemical staining for MR of the dorsal hippocampus, however, did not reveal differences between SHR and WKY rats. SHR showed elevated hypothalamic MR mRNA by qPCR, as well as an increased number of MR immunopositive cells in the magnocellular paraventricular region, compared to WKY rats. By contrast, expression levels of GR mRNA or protein in the hippocampus and hypothalamus of SHR were similar to those of WKY rats. Furthermore, we investigated the role of MR in the hypertensive rats by i.c.v. injection of the MR antagonist RU-2831. This compound produced a significant drop in blood pressure for SHR. In conclusion, MR expression is increased in the hippocampus and hypothalamus of SHR. We suggest that pathological MR overdrive may take responsibility for up-regulation of blood pressure and the encephalopathy of hypertension.

Preventive effects of low molecular mass potassium alginate extracted from brown algae on DOCA salt-induced hypertension in rats

Available evidence indicates that brown algae may be beneficial for the treatment of high blood pressure. Our recent study demonstrated that low molecular mass potassium alginate (L-PA), one of the major polysaccharides extracted from brown algae, decreased systolic blood pressure (SBP) in spontaneous hypertensive rats. The present study investigated the effects of L-PA on deoxycorticosterone acetate (DOCA) salt-induced hypertension in rats. Hypertension was induced by biweekly subcutaneous injections of 50mg/kg DOCA plus 1% NaCl in drinking water. The control group received saline injections. L-PA (250 or 500 mg/kg), KCl (239 mg/kg), or volume-matched solvent was administered orally once daily for 30 days. DOCA salt administration significantly increased SBP, sodium excretion, serum sodium content, circulating plasma volume (CPV), plasma atrial natriuretic peptide (ANP) content, heart and renal weight indices, and mortality and decreased plasma aldosterone (ALD) and serum potassium levels in the vehicle-treated DOCA salt group compared with the control group. However, L-PA dose-dependently normalized the above changes induced by DOCA salt, with the exception of further increasing sodium excretion, while KCl did not affect the changes caused by DOCA salt, with the exception of slightly ameliorating hypokalemia and mortality. These findings suggest that L-PA may offer a novel form of potassium supplementation with greater antihypertensive and sodium excretion actions than KCl and may likely be beneficial for the primary prevention and treatment of hypertension and its cardiovascular sequelae.

Erythrocyte and total body potassium in untreated primary hypertension

In a study of total body and erythrocyte potassium in mild hypertension we found decreased intracellular potassium concentrations in 41 hypertensives compared to controls but no correlation between intracellular potassium, measured by whole body counting, and erythrocyte potassium. A total body potassium corresponding to an intracellular potassium of 85% or less of the expected value was found in females. In the hypertensives, a negative correlation existed between serum and erythrocyte potassium. No correlation was found between potassium decrease and urinary aldosterone or plasma renin level. An inhibition of the active sodium-potassium exchange at the cellular level is proposed as an explanation of these findings.

Eplerenone, a selective aldosterone blocker, in mild-to-moderate hypertension

BACKGROUND

Eplerenone, a selective aldosterone blocker (SAB) that is highly specific for the aldosterone receptor, has the potential to be efficacious in the treatment of hypertension.

METHODS

This 8-week, multicenter, double-blind, placebo-controlled trial assessed the efficacy, safety, and tolerability of eplerenone in eligible patients randomized to eplerenone 50, 100, or 400 mg once daily; eplerenone 25, 50, or 200 mg twice daily; spironolactone 50 mg twice daily; or placebo. The primary efficacy variable was the adjusted mean change in baseline to final visit for seated diastolic blood pressure (DBP).

RESULTS

Of 417 randomized patients, 409 were evaluated for efficacy. The adjusted mean change from baseline to final visit in seated and standing systolic blood pressure (SBP) and DBP was significantly greater (P < .05) in all eplerenone groups than in the placebo group. The adjusted mean change in 24-h ambulatory blood pressure monitoring (ABPM) measurements of SBP and DBP also documented a 24-h duration significantly greater (P < .05) than placebo in eplerenone-treated patients. For all measurements, the antihypertensive effect of eplerenone increased in a dose-response fashion. Eplerenone (100 mg) reduced BP by 75% compared with spironolactone (100 mg) and had an adverse events incidence rate similar to placebo. No antiandrogenic or progestational effects or clinically relevant safety issues were observed in eplerenone-treated patients. However, one spironolactone-treated patient reported menstrual irregularities.

CONCLUSIONS

Eplerenone doses of 50 to 400 mg once daily are well tolerated and effective in reducing BP in patients with mild-to-moderate hypertension during a 24-h period.

Sodium space and intravascular volume: dietary sodium effects in cystic fibrosis and healthy adolescent subjects

OBJECTIVE

To assess the physiologic response to salt depletion in subjects with cystic fibrosis (CF) and control male adolescents for sodium balance, sodium space, and stimulation of the renin-angiotensin-aldosterone axis.

DESIGN

Seven subjects with CF and six controls received a salt-replete (150 or 290 mmol NaCl per day) diet and then a salt-deplete (10 mmol NaCl per day) diet while in a clinical research center.

RESULTS

Space maintenance: CF subjects responded to salt depletion with a greater weight loss than did controls (1.9 vs 0.8 kg) and a decrease in 24Na+ space, whereas controls maintained 24Na+ space. Paired (Na-deplete/Na-replete) blood volumes decreased in subjects with CF, but not in controls. Renin-angiotensin-aldosterone axis stimulation: During salt repletion, subjects with CF had significantly higher aldosterone values than did controls in the afternoon, but not at 7:00 AM. During salt depletion, plasma renin activity and aldosterone increased significantly more in subjects with CF than in controls (renin, 35 vs 13 ng/mL/hour [9.7 vs 3.6 ng.L-1 s-1]; aldosterone: 181 vs 101 ng/dL [5021 vs 2802 pmol/L]). Furthermore, the angiotensin antagonist saralasin increased renin much more in subjects with CF (154 vs 36 ng/mL per hour [43 vs 10 ng.L-1 s-1]). Vasomotor functions: Mean arterial pressure was decreased in subjects with CF on both diets and decreased significantly more with low salt only in subjects with CF. During salt depletion, subjects with CF showed enhanced orthostatic tolerance (less heart rate increase with standing) compared with controls, thus obscuring their volume loss. The blood pressure response to an acute infusion of saralasin suggested that in salt-replete subjects with CF, but not in controls, angiotensin receptors were functional in maintaining vascular tone. During salt depletion, angiotensin was more important for maintenance of blood pressure in subjects with CF than in controls, because the saralasin-induced drop in blood pressure was 20%, ie, close to shock levels, in subjects with CF, and only 6% in controls.

CONCLUSION

The data suggest that patients with CF are so successful in compensating for volume depletion by vigorous activation of the renin-angiotensin system that salt depletion/dehydration cannot be recognized easily by routine clinical measurements, eg, capillary refill, serum sodium levels, or tachycardia.

Physiological significance of plasma sulfoconjugated dopamine in patients with hypertension--clinical and experimental studies

Sulfoconjugated catecholamines, especially dopamine sulfate, have recently attracted much attention because of the possibility of their conversion to active free dopamine by tissue arylsulfatase. In the present study, we have measured the plasma levels of free and sulfoconjugated dopamine in patients with hypertension and have investigated the physiological significance of sulfoconjugation. Results showed that the plasma level of dopamine sulfate in patients with essential hypertension was higher than the level in control subjects, and was highest in patients with renal hypertension. However, the plasma level of free dopamine showed no significant difference between patients with hypertension and normal subjects. Moreover, after normalization of blood pressure in hypertensive patients with medication, the plasma levels of conjugated dopamine decreased to almost the control value. In the experimental study, dopamine sulfate inhibited angiotensin II-induced aldosterone release from bovine adrenal cortical cells to a similar extent as produced by free dopamine. From these results, we have concluded that plasma sulfoconjugated dopamine may regulate free dopamine in the plasma of patients with hypertension, and it may have some physiological effects on blood pressure regulation.

Oral magnesium supplementation improves metabolic variables and muscle strength in alcoholics

Magnesium deficiency is common among chronic alcoholics, but the knowledge of oral magnesium supplementation to this group is limited. We, therefore, randomized 49 chronic alcoholics, moderate to heavy drinkers for at least 10 years to receive oral magnesium or placebo treatment for 6 weeks according to a double-blind protocol. Effects on metabolic variables and muscle strength were analyzed. Significant reduction of aspartate-aminotransferase (ASAT), alanine-aminotransferase (ALAT) and gamma-glutamyl-transpeptidase (GGT) were seen after magnesium, whereas no change was observed with placebo. Bilirubin decreased in both groups. Serum Na, Ca, and P increased significantly during magnesium therapy compared with no statistically significant change in the placebo group. Serum K and Mg increased slightly after magnesium supplementation and decreased in the placebo group, resulting in a significant difference between the two groups at the end of the study. Muscle strength increased significantly during magnesium treatment, contrasting to no change with placebo. Blood pressure, heart rate, hematological variables, serum lipids (cholesterol, HDL, TG), glucose tolerance, and creatinine were unchanged in the two groups after treatment. Alcohol consumption was similar before and during the trial and does not explain the differences between the two groups The results shows that short-term oral magnesium therapy may improve liver cell function, electrolyte status, and muscle strength in chronic alcoholics.

Long term observations in a patient with pseudohypoaldosteronism

This paper describes a patient with severe pseudohypoaldosteronism (PHA) for over 12 years. The patient presented at 10 days of age with a serum sodium of 118 mEq/l and potassium of 12 mEq/l. After failing to maintain normal fluid and electrolyte status with standard therapy, including maximal mineralocorticoid stimulation, he was given a special formula containing minimal potassium plus salt supplements which normalized his electrolyte status. However, when he was 4.5 years of age, an acute gastrointestinal illness led to severe volume depletion, hyperkalemia, and cardiopulmonary arrest. This resulted in significant neurological impairment. At 12.5 years of age, the patient continues to require massive sodium supplements and his diet contains less than 0.5 mEq/kg potassium daily; his height and weight are at the 95th percentile, thus demonstrating that normal growth may be achieved with strict dietary manipulation in a patient with persistent, severe PHA. Serial studies to further define the lesion in this patient have demonstrated: (1) normal binding of aldosterone to aldosterone binding globulin (5.1% bound); (2) normal mineralocorticoid "activity"; (2) suppressible renin and aldosterone levels; (4) increased prostaglandin excretion (3.15 micrograms/g creatinine); (5) lack of benefit of prostaglandin inhibition with indomethacin; (6) normal proximal tubule function (CNa + CH2O = 18.0 ml/100 ml glomerular filtration rate; (7) impaired distal tubule function (CH2O/CNa + CH2O = 79.8%) during water diuresis.

Analysis of the mineralocorticoid receptor in rat heart with the aid of two new spirolactone derivatives

Two derivatives of spirolactone, synthesized in an effort to eliminate the obnoxious side effects of the native molecule, were employed to dissect various aspects of the MR structure and function in rat heart. The introduction of a propyl residue in position 7 of spirolactone produced a molecule (RU 26752) that exhibited an increased affinity for the agonist specific MR, and furthermore revealed an antagonist-specific MR population in the target organ heart but absent from nontarget lung and liver. The specificity for both sites increased when a methoxycarbonyl group was introduced in the 7 position (ZK 91587). RU 26752 labilized the MR at 35 degrees C but did not interfere with thermal activation assessed on DNA-cellulose and sucrose density gradients. ZK 91587 was even more effective in labilizing the MR and did not permit thermal activation at all. Whereas only one ionic species was observed with RU 26752 on DE-52 columns, two were evident with ZK 91587. Both antimineralocorticoids were bound to populations of two molecular sizes on Ultrogel columns. Thus, the nature of chemical substitution in the 7 position of spirolactone dramatically alters the receptor-mediated antisteroid action of the resulting molecule. Such differences may permit distinction between agonist versus the antagonist-specific receptor conformations, and could possibly be exploited for the eventual purification of the mineralocorticoid receptor from various organs.

Is atriopeptin a physiological or pathophysiological substance? Studies in the autoimmune rat

Atriopeptin (AP), a natriuretic-diuretic and vasodilatory peptide, is synthesized and secreted from mammalian atria. The definitive role of this peptide on cardiovascular physiology and pathophysiology has yet to be determined. We developed a population of autoimmune rats sensitized against their own AP to evaluate the consequences of prolonged AP deficiency on physiological and pathophysiological processes. Natriuresis in response to acute intravenous volume expansion was inhibited in the autoimmune rat, however, natriuresis produced by chronic oral salt loading was not suppressed in these animals. Plasma AP increased threefold in the spontaneously hypertensive rat when evaluated as a function of blood pressure. Immunization of these rats had no effect on the rate of development, magnitude of their developing hypertension, or their daily sodium excretion when compared with nonimmunized controls. Mineralocorticoid escape occurred during desoxycorticosterone acetate administration to rats. The ability of rats to escape from the sodium-retaining effects of this steroid was not affected by prior immunization against AP. These results suggest that AP is an important natriuretic substance in response to acute intravascular volume loading. However, atriopeptin does not appear to be involved in the natriuretic response to chronic intravascular volume loading, blood pressure regulation, or mineralocorticoid escape.

Mineralocorticoid-resistant renal hyperkalemia without salt wasting (type II pseudohypoaldosteronism): role of increased renal chloride reabsorption

A rare syndrome has been described in which mineralocorticoid-resistant hyperkalemia of renal origin occurs in the absence of glomerular insufficiency and renal sodium wasting and in which hyperchloremic acidosis, hypertension, and hyporeninemia coexist. The primary abnormality has been postulated to be a defect of the potassium secretory mechanism of the distal nephron. The present studies were carried out to investigate the mechanism of impaired renal potassium secretion in a patient with this syndrome. When dietary intake of sodium chloride was normal, renal clearance of potassium was subnormal (CK/GFR = 3.6 +/- 0.2%; normal subjects, 9.0 +/- 0.9%, N = 4) despite high normal or supernormal levels of plasma and urinary aldosterone. The fractional clearance of potassium remained subnormal (CK/GFR = 5.1 +/- 0.2%) during superimposed chronic administration of superphysiologic doses of mineralocorticoid hormone. Little increase in renal potassium clearance occurred when the delivery of sodium to distal nephron segments was increased further by the i.v. infusion of sodium chloride, despite experimentally sustained hypermineralocorticoidism. But potassium clearance increased greatly when delivery of sodium to the distal nephron was increased by infusion of nonchloride anions: sulfate (sodium sulfate infusion, low sodium chloride diet; CK/GFR = 63.7 +/- 0.4%) or bicarbonate (sodium bicarbonate plus acetazolamide infusion; CK/GFR = 81.7 +/- 1.7%). These findings indicate that mineralocorticoid-resistant renal hyperkalemia in this patient cannot be attributed to the absence of a renal potassium secretory capability or to diminished delivery of sodium to distal nephron segments; instead it may be dependent on chloride delivery to the distal nephron. We suggest that the primary abnormality in this syndrome increases the reabsorptive avidity of the distal nephron for chloride, which (1) limits the sodium and mineralocorticoid-dependent voltage driving force for potassium and hydrogen ion secretion, resulting in hyperkalemia and acidosis and (2) augments distal sodium chloride reabsorption resulting in hyperchloremia, volume expansion, hyporeninemia, and hypertension.

Chromatographic conditions in the expression of corticosteroid receptor specificity

It is shown that cytosol preparations bound with various concentrations of a steroid are necessary to reveal physicochemically distinct, heterogeneous and polymorphic receptors present in the hormone specific target organ, that these cannot be fully appreciated in one-shot experiments at suboptimal steroids levels, and that they escape detection by equilibrium binding and Scatchard analysis alone.

Nuclear binding of steroid receptors: comparison in intact cells and cell-free systems

In regulating gene expression in mammalian tissues, steroid hormones bind to cytoplasmic receptors and the resulting complex associates with the nucleus. In an attempt to study this nuclear association under more precisely controlled conditions, we examined the binding of receptor-[(3)H]steroid complexes to isolated nuclei. Two systems were used: the glucocorticoid-responsive hepatoma cell and the estrogen-sensitive immature rat uterus. Cell-free nuclear binding resembles that observed in the intact cell; it requires the receptor-steroid complex in the appropriate form ("active" complex); it is of high affinity; and it appears to involve about 4000 nuclear acceptor sites per haploid genome. Furthermore, whether binding occurs in intact cells or in cell-free extracts, complexes dissociate from nuclei at similar rates, and the ability of NaCl to extract either type of nuclear-bound complex and the sedimentation velocities of the extracted complexes are identical. Despite these similarities, acceptor sites detected in isolated nuclei differ from those of intact cells, since in neither hepatoma cells nor in the uterus do complexes bound to the nuclei of intact cells prevent further cell-free binding. We conclude that receptor-steroid complexes bind to acceptor sites in isolated nuclei that are chemically similar to, but topographically different from, those of the intact cell.