The Chronic Adverse Effect of Chloroquine on Kidney in Rats through an Autophagy Dependent and Independent Pathways.

BACKGROUND: Chloroquine (CQ), a classic autophagy inhibitor, is used clinically for malaria prophylaxis and pulmonary hypertension treatment. The adverse effects of CQ on morphological and functional changes in the kidney were investigated in the current study due to CQ accumulation in the kidney. METHODS: Twelve male Sprague-Dawley rats were randomly divided into 2 groups for 4 weeks: group 1, control (n = 6); and group 2, CQ administration group (50 mg-1·kg per day ip; n = 6). Serum aldosterone and vasopressin were measured by radioimmunoassay. Immunofluorescence was used to colocalize Tunel with aquaporin 1, aquaporin 2 (AQP2), and Tamm-Horsfall protein. Expression of AQP2 and mineralocorticoid (MR) was detected by western blot and immunohistochemistry. RESULTS: In the present study, 4 weeks of CQ administration were shown to induce severe kidney injury, including glomerular sclerosis and tubular cells apoptosis, especially distal tubular cells. Decreased expression of LC3II/I and p-AKT was demonstrated in CQ-treated rats. Glomerular and proximal tubule injury were associated with impaired autophagy flux, and distal tubule injury may be associated with downregulated cyclic adenosine monophosphate (cAMP)/PKA/AKT signaling. Both MR and AQP2, which are mainly located in the distal tubule and collecting duct, were significantly reduced in CQ-treated rats, thus leading to increased exosomal secretion of AQP2 in urine. Additionally, chronic CQ administration increased aldosterone and vasopressin levels in serum, but lowered the blood pressure, glomerular filtration rate, and urine concentration. CONCLUSIONS: CQ administration damages glomerular, proximal tubule autophagy, and severe distal tubular cells apoptosis by inhibiting cAMP/PKA/AKT signaling.

Identification of mineralocorticoid and glucocorticoid receptors on peripheral nociceptors: Translation of experimental findings from animal to human biology.

Evidence is accumulating that activation of mineralocorticoid (MR) and glucocorticoid (GR) receptors on peripheral sensory neurons modulates pain sensation. While the expression and exact anatomical localization of MR and GR in the various subpopulations of peripheral sensory neurons has been shown in animals, it is still unknown for the human skin. Therefore, we aimed to identify MR and GR mRNA and protein as well as the exact subpopulations of sensory neurons in human versus rat skin. Tissue samples from rat and human skin were subjected to RT-PCR, Western blot and double immunofluorescence confocal analysis of MR and GR with the neuronal markers calcitonin gene-related peptide (CGRP), neurofilament 200 (NF200) and tyrosine hydroxylase (TH). Using RT-PCR we were able to isolate MR as well as GR specific transcripts from human skin. Consistently, Western blot analysis identified MR- as well as GR- specific protein bands at the expected molecular weights of 110 and 87 kD, respectively. Double immunofluorescence confocal microscopy of human skin revealed that MR predominantly colocalized with calcitonin-gene-related peptide (CGRP)-immunoreactive (IR) nociceptive neurons - similar to rat skin - underscoring a pivotal role for MR in the modulation of pain. The majority of GR-immmunoreactivity was localized in peripheral peptidergic CGRP-IR sensory nerve fibers, but in addition on TH-IR sympathetic postganglionic, and NF200-IR myelinated mechanoreceptive nerve fibers, both within human and rat skin. Moreover, GR but not MR were localized in keratinocytes of the epidermal layer of human and rat skin. Overall, our results indicate considerable overlap in sensory neuron expression of MR and GR in humans and rats endorsing a common systems approach in mammals that may modulate the transmission of sensory information by MR and GR activation.

Interactive effects of prenatal alcohol exposure and chronic stress in adulthood on anxiety-like behavior and central stress-related receptor mRNA expression: Sex- and time-dependent effects.

Children and adults prenatally exposed to alcohol show higher rates of mental health problems than unexposed individuals, with depression and anxiety being among the more commonly encountered disorders. Previous studies in rats showed that prenatal alcohol exposure (PAE) can indeed increase depressive- and anxiety-like behavior in adulthood; however, depression and anxiety are often observed in the context of stress and/or a dysregulated stress response system (the hypothalamic-pituitary-adrenal [HPA] axis). PAE can dysregulate the HPA axis, resulting in hyperresponsivity to stress. In turn, this may predispose individuals prenatally exposed to alcohol to the adverse effects of stress compared to unexposed individuals. We have shown previously that PAE animals may be more sensitive to the effects of chronic stress on behavior, showing increased anxiety- and depressive-like behavior following chronic unpredictable stress (CUS) exposure. Here, we investigated the independent and interactive effects of PAE and adult CUS on anxiety-like behavior and receptor systems (corticotropin-releasing hormone receptor type 1 [CRHR1], mineralocorticoid receptor [MR], and glucocorticoid receptor [GR]), and underlying stress and emotional regulation, and whether exposure to CUS differentially results in immediate or delayed effects. Adult male and female offspring from PAE, pair-fed (PF), and ad libitum-fed control (C) dams were exposed to either 10 days of CUS or left undisturbed. Behavioral testing began 1 or 14 days post-CUS, and brains were collected following testing. Anxiety-like behaviors were evaluated using the open field, elevated plus maze and dark-light emergence tests. CRHR1, MR, and GR mRNA expression were assessed in the medial prefrontal cortex (mPFC), amygdala, and hippocampal formation, brain areas key to both stress and emotional regulation. We found that PAE differentially increased anxiety-like behavior and altered GR mRNA in males and females compared to their control counterparts. Furthermore, depending on the timing of testing, CUS unmasked alterations in GR and CRHR1 mRNA expression in the mPFC and amygdala in PAE males, and MR mRNA in the hippocampal formation in PAE females compared to their C counterparts. Overall, the changes observed in these receptor systems may underlie the increase in anxiety-like behavior following PAE and CUS exposure in adulthood. That CUS differentially affected brain and behavioral outcome of PAE and C animals, and did so in a sexually-dimorphic manner, has important implications for understanding the etiology of psychopathology in individuals prenatally exposed to alcohol.

Lactobacillus fermentum NS9 restores the antibiotic induced physiological and psychological abnormalities in rats.

Gut microbiota play a vital role in maintaining the health of the host. Many factors affect gut microbiota; application of broad range antibiotics disturb microbiota, while probiotic application protects the microbiota. To investigate how probiotics alter the physiological and psychological changes induced by antibiotics, we tested the performance of ampicillin-treated rats in the presence or absence of Lactobacillus fermentum strain NS9, in elevated plus maze and Morris water maze. The results showed that NS9 normalised the composition of gut microbiota and alleviated the ampicillin-induced inflammation in the colon. The levels of the mineralocorticoid and N-methyl-D-aspartate receptors were also elevated in the hippocampus of the ampillicin+NS9 treated group. NS9 administration also reduced the anxiety-like behaviour and alleviated the ampicillin-induced impairment in memory retention. These findings suggest that NS9 is beneficial to the host, because it restores the physiological and psychological abnormalities induced by ampicillin. Our results highlight how gut contents regulate the brain, and shed light on the clinical applications of probiotics to treat the side effect of antibiotics and mental disorders.

Maternal depressive symptoms throughout pregnancy are associated with increased placental glucocorticoid sensitivity.

BACKGROUND: Maternal prenatal depression predicts post-partum depression and increases risk of prematurity and low birth weight. These effects may be mediated by altered placental function. We hypothesized that placental function would be influenced by the gestational week of experiencing depressive symptoms and aimed to examine associations between maternal depressive symptoms during pregnancy and placental expression of genes involved in glucocorticoid and serotonin transfer between mother and fetus. METHOD: We studied women participating in a prospective pregnancy cohort: the Prediction and Prevention of Preeclampsia (PREDO) Study, Helsinki, Finland. Maternal depressive symptoms were assessed at 2-week intervals throughout pregnancy in 56 healthy women with singleton, term pregnancies. Messenger ribonucleic acid (mRNA) levels of glucocorticoid (GR) and mineralocorticoid (MR) receptors and serotonin transporter (SLC6A4), 11ß-hydroxysteroid dehydrogenase type 1 (HSD1) and 2 (HSD2) were quantified in placental biopsies. RESULTS: In adjusted analyses women who reported higher depressive symptoms across the whole pregnancy had higher mRNA levels of GR [effect size 0.31 s.d. units, 95% confidence interval (CI) 0.01-0.60, p = 0.042] and MR (effect size 0.34 s.d. units, 95% CI 0.01-0.68, p = 0.047). These effects were significant for symptoms experienced in the third trimester of pregnancy for GR; findings for MR were also significant for symptoms experienced in the second trimester. GR and MR mRNA levels increased linearly by having the trimester-specific depressive symptoms scores 0, 1 or 2-3 times above the clinical cut-off for depression (p = 0.003, p = 0.049, respectively, and p = 0.004, p = 0.15 in adjusted analyses). CONCLUSIONS: Our findings offer potential gestational-age-specific mechanisms linking maternal depressive symptoms during pregnancy via placental biology. Future studies will test whether these also link with adverse offspring outcomes.

Imaging of corticosteroid receptors in live cells.

Adrenal corticosteroids (cortisol in humans or corticosterone in rodents) exert numerous effects on the central nervous system that regulate the stress response, mood, learning, and memory, and various neuroendocrine functions. The actions of corticosterone (CORT) in the brain are mediated via two receptor systems: the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR). It has been shown that the MR and GR are highly co-localized in the hippocampus. These receptors are mainly localized in the cytoplasm, and are translocated into the nucleus, after binding with hormones, to act as transcriptional factors. Thus, the subcellular dynamics of both receptors constitute one of the most important issues to be clarified. Given the differential actions of MR and GR in the central nervous system, it is of great consequence to elucidate how MR and GR are trafficked between the cytoplasm and nucleus and how their interactions are regulated by hormones and/or other molecules to exert their functional activities. In this chapter, we describe our recent studies of corticosteroid receptor dynamics in living cells, focusing on three points: (1) time-lapse imaging of green fluorescent protein (GFP)-labeled corticosteroid receptors; (2) intranuclear dynamics of GFP-labeled corticosteroid receptors using the technique of fluorescence recovery after photobleaching; and (3) the possibility of heterodimer formation using the fluorescence resonance energy transfer technique. We discuss various factors affecting the dynamics of these receptors. Furthermore, we present future directions in the in vivo molecular imaging of corticosteroid receptors at the whole brain level.

Mineralocorticoid receptor expression in human penile corpus cavernosum.

OBJECTIVES: Mineralocorticoid receptor (MR) is known to play physiological and pathophysiological roles in the cardiovascular system, and MR activation directly damages these organs. The aim of this study was to evaluate the expression of MR and 11ß-hydroxysteroid dehydrogenase type 2 (11ß-HSD2) in the human penile corpus cavernosum. METHODS: MR and 11ß-HSD2 expression was assayed in human penile tissues, and also in human renal tissues as a positive control. Expressions of MR mRNA and 11ß-HSD2 mRNA were evaluated using reverse transcription polymerase chain reaction (RT-PCR). MR and 11ß-HSD2 were visually identified using immunofluorescence analysis. RESULTS: MR mRNA expression in human penis was confirmed by RT-PCR. On quantitative RT-PCR analysis, 11ß-HSD2 mRNA expression was detected at minimal levels in penile tissue. Immunofluorescence analysis revealed positive staining for MR and negative staining for 11ß-HSD2 in smooth muscle cells of the corpus cavernosum. CONCLUSIONS: This study demonstrated the presence of MR and the absence of 11ß-HSD2 in human penile corpus cavernosum. Considering that MR activation causes various organ damages, MR blockade in human penile corpus cavernosum may have therapeutic benefits. Investigations for the penile effects of MR activation have the potential to provide new treatment approaches for erectile dysfunction.

Mineralocorticoid receptor activation and blockade: an emerging paradigm in chronic kidney disease.

Slowing the progression of chronic kidney diseases (CKDs) requires new and effective treatment approaches. Aldosterone classically acts on the distal nephron: it facilitates sodium reabsorption, potassium secretion, and participates in blood pressure control. Recently, new targets of aldosterone have been described including the heart and the vasculature, and other kidney cells such as mesangial cells, podocytes, and renal fibroblasts. The pathophysiological implications of increased mineralocorticoid receptor (MR) expression and activation (either dependent on aldosterone or direct ligand-independent activation) and its blockade have been illustrated with ex vivo in cell cultures and in vivo in experimental animal models of CKD, including diabetic and hypertensive nephropathies, and glomerulopathies. The beneficial effects of the MR antagonists are independent of the hypertensive effect of aldosterone, indicating that blocking the activation of the MR may have unique clinical importance. Several studies have reported efficacy and safety studies with spironolactone or eplerenone in patients with kidney diseases. In this review, we discuss the recent results reported in experimental and clinical research in this field, and emphasize the direct activation of the MR that can occur in pathological states associated with CKD, even in the absence of increased circulating levels of aldosterone.

Rapid effects of corticosterone in the mouse dentate gyrus via a nongenomic pathway.

Corticosterone activates two types of intracellular receptors in the rodent brain: the high affinity mineralocorticoid receptor (MR) and lower affinity glucocorticoid receptor (GR). These receptors act as transcriptional regulators and mediate slow changes in neuronal activity in a region-dependent manner. For example, in CA1 pyramidal cells, corticosterone slowly changes Ca(2+) currents and glutamate transmission but dentate granule cells appear to be resistant. Recent studies have shown that corticosteroids also exert rapid MR-dependent, nongenomic effects on hippocampal CA1 cells [e.g. increasing the frequency of miniature excitatory postsynaptic currents (mEPSCs)]. In the present study, we investigated whether dentate granule cells are also resistant to the rapid effects of corticosterone. We found that, comparable to the CA1 area, corticosterone quickly and reversibly increases mEPSC frequency but not amplitude of dentate cells. This effect did not require protein synthesis and displayed the pharmacological profile of an MR- rather than GR-dependent event. These data support the hypothesis that, unlike the slow gene-mediated effects of corticosterone, rapid hormonal actions are quite similar for CA1 and dentate cells.

Chronic corticosterone administration from adolescence through early adulthood attenuates depression-like behaviors in mice.

There is evidence that depression may have a different neural basis at different ages. Although chronic stress and elevated glucocorticoid levels have been demonstrated to lead to the emergence of mood disorders, it remains unclear how moderate elevation of glucocorticoid levels in young animals influences depression-like behaviors and brain functions. To address this issue, the present study examines how chronic corticosterone (CORT) administration during adolescence and early adulthood influences depression-like behaviors, hypothalamic-pituitary-adrenal (HPA) axis response and hippocampal cell proliferation. Male mice were chronically administrated with CORT drinking water (20mg/L) during adolescence. After two months of treatment, serum CORT levels were measured using enzyme immunoassay. Hippocampal glucocorticoid and mineralocorticoid receptors were characterized using Western blot. Tail suspension and forced swim tests were used to assess depression-related behaviors in mice. Immunohistochemistry was performed to measure bromodeoxyuridine (BrdU) incorporation in order to assess cell proliferation in the hippocampus. Our results suggest that chronic CORT administration induced a mild but not significant elevation in basal CORT levels and attenuated the physiological responses to stress. Chronic CORT administration also reduced expression of the hippocampal mineralocorticoid receptor and decreased immobility time in both the tail suspension test and the forced swim test. Moreover, chronic CORT administration increased the BrdU immunoreactivities in the hippocampus. Taken together, these findings suggest that chronic mild elevation by CORT administration during the adolescence and early adulthood attenuates depression-like behaviors.

Effect of neonatal handling on adult rat spatial learning and memory following acute stress.

Brief neonatal handling permanently alters hypothalamic-pituitary-adrenal axis function resulting in increased ability to cope with stress. Since stress is known to affect cognitive abilities, in the present study we investigated the effect of brief (15 min) handling on learning and memory in the Morris water maze, following exposure to an acute restraint stress either before training or recall. Exposure of non-handled rats to the acute stress prior to training resulted in quicker learning of the task, than in the absence of the stressor. When acute stress preceded acquisition, male handled rats showed an overall better learning performance, and both sexes of handled animals were less impaired in the subsequent memory trial, compared to the respective non-handled. In addition, the number of neurons immunoreactive for GR was higher in all areas of Ammon's horn of the handled rats during the recall. In contrast, the number of neurons immunoreactive for MR was higher in the CA1 and CA2 areas of the non-handled males. When the acute restraint stress was applied prior to the memory test, neonatal handling was not effective in preventing mnemonic impairment, as all animal groups showed a similar deficit in recall. In this case, no difference between handled and non-handled rats was observed in the number of GR positive neurons in the CA2 and CA3 hippocampal areas during the memory test. These results indicate that early experience interacts with sex and acute stress exposure in adulthood to affect performance in the water maze. Hippocampal corticosterone receptors may play a role in determining the final outcome.

Identification of the mineralocorticoid receptor in human spermatozoa.

Aldosterone seems to play a role in the regulation of the electrolyte content of sperm and in the motility of spermatozoa. The aim of the study was to evaluate the presence of the mineralocorticoid receptor (MR) in human ejaculated spermatozoa. We have assayed MR on spermatozoa of freshly ejaculated sperm from healthy donors. The identification of MR was made by using immunohistochemistry and immunofluorescence analyses, while MR mRNA expression was evaluated by real-time PCR assay. The immunohistochemical and immunofluorescence analyses showed positive staining both in the midpiece and in the tail of the spermatozoa. Relative quantification of MR by using real-time PCR shows that the mRNA expression of MR in spermatozoa is lower than in mononuclear leukocytes (positive controls). Sequencing showed complete identity between the sequence obtained from spermatozoa and the human MR cDNA sequence. Further studies should be performed in order to elucidate a possible physiological role of aldosterone in regulating electrolyte concentration, and the pro-oxidant effect of excess aldosterone in this new target tissue.

AAV delivery of mineralocorticoid receptor shRNA prevents progression of cold-induced hypertension and attenuates renal damage.

UNLABELLED: The aim of this study was to determine the effect of RNA interference inhibition of mineralocorticoid receptor (MR) on cold-induced hypertension (CIH) and renal damage. Recombinant adeno-associated virus (AAV) carrying short hairpin small interference (si)RNA for MR (AAV.MR-shRNA) was constructed and tested for the ability to inhibit renal MR and to control CIH. Three groups of rats with CIH received AAV.MR-shRNA (1.25 x 10(9) particles/rat, intravenous), AAV carrying scrambled shRNA (AAV.Control-shRNA) (1.25 x 10(9) particles/rat, intravenous) and phosphate buffer solution (PBS), respectively. All rats were kept in a cold chamber (6.7 degrees C) throughout the experiment. Adeno-associated virus delivery of MR-shRNA prevented progression of CIH. Blood pressure (BP) of the AAV.MR-shRNA-treated group did not increase and remained at 145+/-3 mm Hg, whereas BP of the AAV.Control-shRNA-treated and PBS-treated group increased to 167+/-4 and 161+/-3 mm Hg, respectively, at 3 weeks after gene delivery. Thus, the antihypertensive effect of a single injection of AAV.MR-shRNA lasted for at least 3 weeks (length of the study). Adeno-associated virus carrying short hairpin siRNA for MR significantly increased urinary sodium excretion and decreased proteinuria. It also decreased serum creatinine and blood urea nitrogen, suggesting enhanced renal function. Both Western blot and immunohistochemical analysis showed that MR expression was decreased significantly in the kidney in the AAV.MR-shRNA-treated rats, confirming that renal MR is effectively inhibited by AAV.MR-shRNA. Adeno-associated virus carrying short hairpin siRNA for MR also significantly attenuated renal hypertrophy. In addition, AAV delivery of MR-shRNA prevented atrophy and dilation of renal tubules and abolished tubular deposition of proteinaceous material seen in CIH rats. CONCLUSIONS: (1) AAV delivery of MR-shRNA effectively silenced MR in vivo. (2) RNA interference inhibition of MR may open a new avenue for the long-term control of hypertension and renal damage.

Aldosterone target neurons in the nucleus tractus solitarius drive sodium appetite.

Sodium appetite can be enhanced by the adrenal steroid aldosterone via an unknown brain mechanism. A novel group of neurons in the nucleus tractus solitarius expresses the enzyme 11-beta-hydroxysteroid dehydrogenase type 2, which makes them selectively responsive to aldosterone. Their activation parallels sodium appetite in different paradigms of salt loss even in the absence of aldosterone. These unique aldosterone target neurons may represent a previously unrecognized central convergence point at which hormonal and neural signals can be integrated to drive sodium appetite.

Changes in basal hypothalamo-pituitary-adrenal activity during exercise training are centrally mediated.

The effects of exercise training on hypothalamo-pituitary-adrenal (HPA) function are unclear. We investigated whether pituitary-adrenal adaptation during exercise training is mediated by changes in neuropeptide and corticosteroid receptor gene expression in the brain and pituitary. Sprague-Dawley rats were subject to either daily swimming (DS) or sham exercise (SE) for 45 min/day, 5 days/week, for 2 (2W), 4 (4W), or 6 wk (6W) (n = 7-10/group). Corticosterone (Cort) and catecholamine responses during swimming were robust at 6W compared with 2W and 4W, indicating that HPA response to exercise during training is not attenuated when absolute intensity is progressively increased. In DS, basal (morning) plasma ACTH and Cort levels increased from 2W to 4W but plateaued at 6W, whereas in SE, they increased from 4W to 6W, with 6W values higher than in DS. In DS, there was a transient decrease in glucocorticoid receptor (GR) mRNA in the paraventricular nucleus (PVN) and pituitary and a transient increase in corticotrophin-releasing hormone (CRH) mRNA. In contrast, hippocampal mineralocorticoid receptor mRNA and PVN GR mRNA decreased from 4W to 6W in SE, with 6W values lower than in DS. These findings suggest that exercise training prevents an elevation in basal pituitary-adrenal activity potentially via transient alterations in the gene transcription of PVN and pituitary GR as well as CRH to suppress central drive to the HPA axis. In contrast, the increase in basal pituitary-adrenal activity with repeated sham exercise appears to be associated with decreases in hippocampal MR and PVN GR mRNA expression.

Aldosterone directly induces myocyte apoptosis through calcineurin-dependent pathways.

BACKGROUND: Aldosterone has recently attracted considerable attention for its involvement in the pathophysiology of heart failure, in which apoptotic cell loss plays a critical role. This study examined whether aldosterone directly induces myocyte apoptosis via its specific receptors. METHODS AND RESULTS: Neonatal rat cardiac myocytes were exposed to aldosterone (10(-8) to 10(-5) mol/L). Nuclear staining with Hoechst 33258 showed that aldosterone induced myocyte apoptosis in a dose- and time-dependent fashion. Treatment of myocytes with 10(-5) mol/L aldosterone significantly increased the percentage of apoptosis (15.5+/-1.4%) compared with serum-deprived control (7.3+/-0.6%). Radio ligand binding assay revealed the existence of plasma membrane receptor with high affinity (K(d), 0.2 nmol/L) for aldosterone in cardiac myocytes but not in fibroblasts. Aldosterone rapidly (approximately 30 seconds) mobilized [Ca2+]i that was blocked by neomycin. Aldosterone induced dephosphorylation of the proapoptotic protein Bad, enhancement of mitochondrial permeability transition, decrease in mitochondrial membrane potential, and release of cytochrome c from the mitochondria into the cytosol with concomitant activation of caspase-3. These effects of aldosterone were inhibited by concurrent treatment with either an L-type Ca2+ channel antagonist, nifedipine, or inhibitors for the Ca2+-dependent phosphatase calcineurin, cyclosporin A and FK506. CONCLUSIONS: The present study demonstrates for the first time that the specific plasma membrane receptor (coupled with phospholipase C) for aldosterone is present on cardiac myocytes and that aldosterone accelerates the mitochondrial apoptotic pathway through activation of calcineurin and dephosphorylation of Bad, suggesting that the proapoptotic action of aldosterone may directly contribute to the progression of heart failure.

Enhancement of glucocorticoid and mineralocorticoid receptor density in the microcirculation of the spontaneously hypertensive rat.

OBJECTIVE: Elevated blood pressure and abnormal physiological parameters in the microcirculation of the spontaneously hypertensive rat (SHR) can be normalized by adrenalectomy. Thus glucocorticoids and mineralocorticoids may have major control over blood pressure status and organ injury mechanisms in SHRs. As background, this study was designed to examine the distribution of the glucocorticoid and mineralocorticoid receptors in a microvascular network. METHODS: Mature SHR and their normotensive controls, the Wistar-Kyoto (WKY) rat, were studied. An immunohistochemical method was developed that provides a comprehensive display of the receptors in all segments of the mesentery microcirculation and the surrounding tissue parenchyma. RESULTS: All cells in the mesentery exhibit immunolabeling of the glucocorticoid receptor with predominant expression in the nuclei of parenchymal and endothelial cells. The mineralocorticoid receptor is expressed also in most cells of the microcirculation and adjacent parenchymal tissue. Both receptors exhibit the highest levels of immunolabel in the wall of the arterioles and venules, with lower levels in capillaries. Compared with WKY rats, the SHRs exhibit significantly enhanced density of glucocorticoid and mineralocorticoid receptors in endothelial cells of arterioles and venules as well as in parenchymal cells. CONCLUSIONS: These results suggest that the enhanced sensitivity of the SHR to glucocorticoids and aldosterone may be in part associated with enhanced glucocorticoid and mineralocorticoid receptor densities in the microcirculation.

Pharmacology and physiology of ovine corticosteroid receptors.

The aim of these studies was to characterize the ovine corticosteroid receptors (MR, mineralocorticoid receptors and GR, glucocorticoid receptors) in ovine hippocampus and brainstem. Adrenal-intact and adrenalectomized ewes were studied; adrenalectomized ewes were killed 47 +/- 9 h after steroid withdrawal, when symptoms of hypotension and/or hyperkalemia became evident. RT-PCR, immunoblotting and pharmacologic studies indicated the presence of both MR and GR in hippocampus and brainstem. Competitive binding studies using 3H-cortisol in brain tissue showed that the ovine MR binds cortisol, aldosterone and progesterone with equal affinity. Differences in receptor availability in intact and adrenalectomized ewes, along with determination of the binding affinity (K(d)) of MR and GR, suggested that MR occupancy is about 90%, whereas GR occupancy is about 30%, in normal animals. There was a significant increase in protein level of MR in brainstem, and the appearance of a higher molecular weight band for MR in hippocampus following steroid withdrawal, however no significant change in mRNA was detected by semiquantitative RT-PCR for either MR or GR in hippocampus or brainstem following steroid withdrawal. These studies suggest that physiological ligands of MR in the sheep brain include progesterone and cortisol, and that, as in other species, affinity of MR for cortisol is greater than that of GR.

Comparison of central corticosteroid receptor expression in male Lewis and Fischer rats.

The histocompatible inbred Lewis (LEW) and Fischer (F344) rat strains exhibit marked phenotypic differences in the hormonal activity of the hypothalamic-pituitary-adrenal (HPA) axis. As such they provide an important comparative model for the study of HPA regulation including the central feedback regulation by the glucocorticoid transcription factors, the mineralocorticoid receptor (MR) and the glucocortiocoid receptor (GR). In adult male rats, basal nadir plasma corticosterone values were similar in the two strains whereas the amplitude and duration of the corticosterone response to restraint were significantly reduced in LEW. MR and GR mRNA expression were compared in LEW and F344 throughout the rostrocaudal extent of the hippocampus. Hippocampal MR expression was consistent throughout the rostrocaudal extent and similar in F344 and LEW males. Hippocampal GR expression was consistent throughout the rostrocaudal extent, but significantly greater in the rostral dentate gyrus and Cornu ammonis subfields in LEW males compared with F344 males. The LEW phenotype of relatively high hippocampal GR expression and HPA hypoactivity is shared by outbred rats exposed to neonatal handling and GR-overexpressing transgenic mice. Whether or not this relationship is causal, as well as the functional significance of the rostral-extent specific GR difference, remains to be elucidated.