Corticosterone Secretion In Rats Research Articles

A double ovulation protocol for Xenopus laevis produces doubled fertilisation yield and moderately transiently elevated corticosterone levels without loss of egg quality.

The African claw-toed frog, Xenopus laevis, is a well-established laboratory model for the biology of vertebrate oogenesis, fertilisation, and development at embryonic, larval, and metamorphic stages. For ovulation, X. laevis females are usually injected with chorionic gonadotropin, whereupon they lay typically hundreds to thousands of eggs in a day. After being rested for a minimum of three months, animals are re-used. The literature suggests that adult females can lay much larger numbers of eggs in a short period. Here, we compared the standard "single ovulation" protocol with a "double ovulation" protocol, in which females were ovulated, then re-ovulated after seven days and then rested for three months before re-use. We quantified egg number, fertilisation rate (development to cleavage stage), and corticosterone secretion rate as a measure of stress response for the two protocol groups over seven 3-month cycles. We found no differences in egg number-per-ovulation or egg quality between the groups and no long-term changes in any measures over the 21-month trial period. Corticosterone secretion was elevated by ovulation, similarly for the single ovulation as for the first ovulation in the double-ovulation protocol, but more highly for the second ovulation (to a level comparable to that seen following shipment) in the latter. However, both groups exhibited the same baseline secretion rates by the time of the subsequent cycle. Double ovulation is thus transiently more stressful/demanding than single ovulation but within the levels routinely experienced by laboratory X. laevis. Noting that "stress hormone" corticosterone/cortisol secretion is linked to physiological processes, such as ovulation, that are not necessarily harmful to the individual, we suggest that the benefits of a doubling in egg yield-per-cycle per animal without loss of egg quality or signs of acute or long-term harm may outweigh the relatively modest and transient corticosterone elevation we observed. The double ovulation protocol therefore represents a potential new standard practice for promoting the "3Rs" (animal use reduction, refinement and replacement) mission for Xenopus research.

A Novel Automated System Yields Reproducible Temporal Feeding Patterns in Laboratory Rodents

ABSTRACTBackgroundThe impact of temporal feeding patterns remains a major unanswered question in nutritional science. Progress has been hampered by the absence of a reliable method to impose temporal feeding in laboratory rodents, without the confounding influence of food-hoarding behavior.ObjectiveThe aim of this study was to develop and validate a reliable method for supplying crushed diets to laboratory rodents in consistent, relevant feeding patterns for prolonged periods.MethodsWe programmed our experimental feeding station to deliver a standard diet [StD; Atwater Fuel Energy (AFE) 13.9% fat] or high-fat diet (HFD; AFE 45% fat) during nocturnal grazing [providing 1/24th of the total daily food intake (tdF/I) of ad libitum–fed controls every 30 min] and meal-fed (3 × 1-h periods of ad libitum feeding) patterns in male rats (Sprague-Dawley: 4 wk old, 72–119 g) and mice [C57/Bl6J wild-type (WT): 6 mo old, 29–37 g], and ghrelin-null littermates (Ghr−/−; 27–34 g).ResultsGrazing yielded accurate, consistent feeding events in rats, with an approximately linear rise in nocturnal cumulative food intake [tdF/I (StD): 97.4 ± 1.5% accurate compared with manual measurement; R2 = 0.86; tdF/I (HFD): 99.0 ± 1.4% accurate; R2 = 0.86]. Meal-feeding produced 3 nocturnal meals of equal size and duration in StD-fed rats (tdF/I: 97.4 ± 0.9% accurate; R2 = 0.90), whereas the second meal size increased progressively in HFD-fed rats (44% higher on day 35 than on day 14; P < 0.01). Importantly, cumulative food intake in grazing and meal-fed rats was identical. Similar results were obtained in WT mice except that less restricted grazing induced hyperphagia (compared with meal-fed WT mice; P < 0.05 from day 1). This difference was abolished in Ghr−/− mice, with meal initiation delayed and meal duration enhanced. Neither pattern elevated corticosterone secretion in rats, but meal-feeding aligned ultradian pulses.ConclusionsWe have established a consistent, measurable, researcher-defined, stress-free method for imposing temporal feeding patterns in rats and mice. This approach will facilitate progress in understanding the physiologic impact of feeding patterns.

Effects of different claw-shortening devices on claw condition, fear, stress, and feather coverage of layer breeders

Natural mating colony cage systems for parent-stock layer breeders have been widely adopted by many commercial farms in China. However, the environment is still relatively barren, so enrichment devices such as claw abrasives can be provided. Hens living in wire cages lack the opportunity to abrade their claws, resulting in uncontrolled claw growth. The objective of this study was to investigate the effects of claw abrasive devices (CADs). Three different CADs were investigated: abrasive strips (T1), metal plates with holes (T2) and rubber mats with grooves (T3); cages without CADs acted as controls (T4). Claw length and sharpness, foot health, feather coverage, fear and physiological stress and mortality of the layer breeders were evaluated. Twelve replicates were used for each treatment, a total of 48 identical cages. Results showed that CADs had significant effects on claw length and sharpness of both hens and roosters. Birds in the T1 group had the shortest claw length and bluntest claw sharpness at 22, 32, 42, and 52 wk of age (P < 0.05). T1, T2, and T3 had higher scores for claw condition and significantly better overall plumage condition on the back and rump than T4 (P < 0.05). Hens in the T4 group were more susceptible to the tonic immobility, novel object, and avoidance distance tests. No significant differences were found between groups in concentration of triiodothyronine, thyroxine or 5-HT, except a significantly higher concentration of corticosterone in T4 compared to T1, T2, and T3 (P < 0.05). Overall mortality and mortality from cannibalism were both significantly higher in T4 than in T1, T2, and T3 (P < 0.05). In conclusion, hens with access to CADs during the laying period had shorter and blunter claws, less damaged plumage, a lower plasma corticosterone secretion and mortality rate and were less fearful.

Stress and hypertensive disease: adrenals as a link. Experimental study on hypertensive ISIAH rat strain

ABSTRACTObjective: Association between stress and hypertensive disease is still a matter of debate. Can stress be the cause of hypertensive disease and, if so, what mechanisms are involved? To clarify this question, the Inherited stress-induced arterial hypertensive rat strain (ISIAH rat strain) with a stress related arterial hypertension was developed by selection for the enhanced blood pressure response to 0.5 h restraint stress. The main intention of this work is to confirm that the adrenals are a main link between stress and hypertensive disease. Methods: Hypertensive ISIAH and normotensive WAG rats have been studied. The in vivo secretion rate of corticosterone, aldosterone, 11-Deoxycorticosterone (DOC), and 11-dehydrocorticosterone was measured in anesthetized rats by adrenal vein cannulation. The Dexamethasone/Adrenocorticotropic hormone (DEX/ACTH) test was performed and mRNA expression of Cyp11b1 and Cyp11b2 genes in adrenals was evaluated by real-time PCR. Results: An increased secretion rate of corticosterone and DOC and higher peripheral plasma aldosterone concentration in ISIAH rats were revealed. Response of plasma aldosterone to the surgical stress (adrenal vein cannulation) in the ISIAH rats was significantly higher. The increase of corticosterone and aldosterone in response to ACTH was also higher in hypertensive rats. The basal mRNA expression of both Cyp11b1 and Cyp11b2 genes was increased in the ISIAH rats. The ratio 11-dehydrocorticosterone/corticosterone in ISIAH rats was low which indicates the weakening of 11-beta-Hydroxysteroid dehydrogenase (11-beta-HSD) type 2 converting corticosterone to cortisone. Conclusion: ISIAH rats may serve as a living proof that stress may produce sustained hypertension, and genetically determined enhanced stress responsiveness of corticosterone and, especially, aldosterone may play a crucial role in the mechanism of hypertension development.

Presentation of noise during acute restraint stress attenuates expression of immediate early genes and arginine vasopressin in the hypothalamic paraventricular nucleus but not corticosterone secretion in rats

The present study investigated the effect of acoustic stimulation on the activation of the hypothalamic-pituitary-adrenal (HPA) axis in rats submitted to acute restraint stress, through semi-quantitative histochemical analysis of expression of immediate early gene products (c-Fos, JunB and phosphorylated c-Jun) and arginine vasopressin (AVP) hnRNA in the paraventricular nucleus (PVN). Simultaneous presentation of white or pink noise with restraint resulted in a significant attenuation of stress-induced c-Fos and JunB expression in the dorsal body of dorsal medial parvicellular subdivision (mpdd) of the PVN, as compared with restraint without noise. However, this presentation did not change phosphorylation of c-Jun and the plasma corticosterone level. Moreover, white noise presentation during restraint led to a reduction in the number of c-Fos- or JunB-expressing corticotropin-releasing hormone (CRH) neurons and the number of neurons expressing AVP hnRNA in the mpdd. Dual-histochemical labeling revealed co-expression of c-Fos and JunB, as well as JunB and AVP hnRNA in mpdd neurons. These data suggest that acoustic stimuli have an attenuation effect on the restraint-induced activation of neuroendocrine CRH neurons, resulting in the reduction in AVP production as an adaptation of HPA axis to repeated stress.

Constant light disrupts the circadian rhythm of steroidogenic proteins in the rat adrenal gland

The circadian rhythm of corticosterone (CORT) secretion from the adrenal cortex is regulated by the suprachiasmatic nucleus (SCN), which is entrained to the light–dark cycle. Since the circadian CORT rhythm is associated with circadian expression of the steroidogenic acute regulatory (StAR) protein, we investigated the 24h pattern of hormonal secretion (ACTH and CORT), steroidogenic gene expression (StAR, SF-1, DAX1 and Nurr77) and the expression of genes involved in ACTH signalling (MC2R and MRAP) in rats entrained to a normal light–dark cycle. We found that circadian changes in ACTH and CORT were associated with the circadian expression of all gene targets; with SF-1, Nurr77 and MRAP peaking in the evening, and DAX1 and MC2R peaking in the morning. Since disruption of normal SCN activity by exposure to constant light abolishes the circadian rhythm of CORT in the rat, we also investigated whether the AM–PM variation of our target genes was also disrupted in rats exposed to constant light conditions for 5weeks. We found that the disruption of the AM–PM variation of ACTH and CORT secretion in rats exposed to constant light was accompanied by a loss of AM–PM variation in StAR, SF-1 and DAX1, and a reversed AM–PM variation in Nurr77, MC2R and MRAP. Our data suggest that circadian expression of StAR is regulated by the circadian expression of nuclear receptors and proteins involved in both ACTH signalling and StAR transcription. We propose that ACTH regulates the secretion of CORT via the circadian control of steroidogenic gene pathways that become dysregulated under the influence of constant light.

Inhibition of immobilization stress-induced anorexia, behavioral deficits, and plasma corticosterone secretion by injected leptin in rats

Leptin, originally identified as an anti-obesity hormone, also has an important role in the regulation of mood and emotion. The present study was designed to monitor effects of injected leptin on immobilization stress-induced anorexia, behavioral deficits, and plasma corticosterone secretion in rats. Exposure to 2 h immobilization stress decreased food intake and body weight in saline-injected animals. Animals exposed to open field, elevated plus maze, and light–dark transition tests the day following immobilization exhibited anxiety-like behavior. Leptin injected at doses of 0.1 and 0.5 mg/kg also decreased food intake and body weight in unstressed animals and elicited anxiolytic effects at dose of 0.5 mg/kg, monitored on the following day. Immobilization-induced decreases in food intake, body weight, as well as stress-induced behavioral deficits in the open field, elevated plus maze, and light–dark transition test were reversed by exogenous leptin in a dose-dependent (0.1–0.5 mg/kg) manner. Acute exposure to 2 h immobilization produced a fourfold rise in plasma levels of corticosterone. Animals injected with leptin at a dose of 0.1 mg/kg, but not at dose of 0.5 mg/kg, exhibited a marginal increase in plasma corticosterone. Immobilization-induced increases of plasma corticosterone were reversed by leptin injected at doses of 0.1 or 0.5 mg/kg. The data suggest that exogenous leptin can reduce stress perception, resulting in an inhibition of stress effects on the activity of hypothalamic-pituitary-adrenal axis and behavior. The reported pharmacological effects of leptin represent an innovative approach for the treatment of stress-related disorders.

Neuropeptide W stimulates adrenocorticotrophic hormone release &lt;i&gt;via&lt;/i&gt; corticotrophin-releasing factor but not &lt;i&gt;via&lt;/i&gt; arginine vasopressin

Neuropeptide W (NPW) was isolated as an endogenous ligand for NPBWR1, an orphan G protein-coupled receptor localized in the rat brain, including the paraventricular nucleus. It has been reported that central administration of NPW stimulates corticosterone secretion in rats. We hypothesized that NPW activates the hypothalamic-pituitary-adrenal (HPA) axis via corticotrophin-releasing factor (CRF) and/or arginine vasopressin (AVP). NPW at 1 pM to 10 nM did not affect basal or ACTH-induced corticosterone release from dispersed rat adrenocortical cells, or basal and CRF-induced ACTH release from dispersed rat anterior pituitary cells. In conscious and unrestrained male rats, intravenous administration of 2.5 and 25 nmol NPW did not affect plasma ACTH levels. However, intracerebroventricular (icv) administration of 2.5 and 5.0 nmol NPW increased plasma ACTH levels in a dose-dependent manner at 15 min after stimulation (5.0 vs. 2.5 nmol NPW vs. vehicle: 1802 ± 349 vs. 1170 ± 204 vs. 151 ± 28 pg/mL, respectively, mean ± SEM). Pretreatment with astressin, a CRF receptor antagonist, inhibited the increase in plasma ACTH levels induced by icv administration of 2.5 nmol NPW at 15 min (453 ± 176 vs. 1532 ± 343 pg/mL, p<0.05) and at 30 min (564 ± 147 vs. 1214 ± 139 pg/mL, p<0.05) versus pretreatment with vehicle alone. However, pretreatment with [1-(β-mercapto-β, β-cyclopentamethylenepropionic acid), 2-(Ο-methyl)tyrosine]-arg-vasopressin, a V1a/V1b receptor antagonist, did not affect icv NPW-induced ACTH release at any time (p>0.05). In conclusion, we suggest that central NPW activates the HPA axis by activating hypothalamic CRF but not AVP.

Neonatal asphyxia under hyperthermic conditions alters HPA axis function in juvenile rats

Neonatal anoxia is an example of early-life threatening experience that might exert long-lasting behavioral disturbance. One of the consequences of neonatal asphyxia is hyperactivity in open-field test. Changes in open-field activity are coupled with changes in the function of the hypothalamic–pituitary–adrenal (HPA) axis. A critical determinant of the severity of hypoxic–ischemic brain injury in newborn rats is body temperature. Hyperthermia under anoxic conditions increases locomotor activity in the open-field test. Therefore, the aim of the present study was to test whether body temperature during neonatal anoxia can affect basal and stress-induced corticosterone secretion in rats. At the age of 2 days Wistar rat pups were exposed to anoxia in 100% nitrogen atmosphere. Rectal temperature was kept at 33 °C (typical for the rat pups), or was elevated to a level typical for febrile adults (39 °C). Control rats were exposed to atmospheric air under the respective thermal conditions. Basal and stress-induced corticosterone levels were assessed using sulphuric acid-induced fluorescence, on postnatal day 14. Body temperature during neonatal asphyxia altered the early developmental profile of plasma corticosterone. Hyperthermia under anoxic conditions decreased the corticosterone response to open-field stress. In conclusion, febrile body temperature changes corticosterone release, which might induce neurobehavioral disturbances. On the other hand, a protection against the HPA dysfunction can be achieved by the reduced physiological neonatal body temperature.

Steroidogenic acute regulatory protein gene expression, steroid-hormone secretion and proliferative activity of adrenocortical cells in the presence of proteasome inhibitors: In vivo studies on the regenerating rat adrenal cortex

Previous studies have shown that proteasome inhibitors promote the accumulation of steroidogenic acute regulatory protein (StAR) in cultured rat adrenocortical cells. Unexpectedly, this response was associated with a moderate lowering in the corticosterone secretion and proliferation rate of cultured cells. Hence, we studied the effects of proteasome inhibitors MG115 and MG132 on the secretion and proliferative activity of the regenerating adrenal cortex in rats 5 days after surgery. Animals were given two subcutaneous injections of 0.15 or 1.5 nmol/100 g of inhibitors 24 and 12 h before decapitation. Real-time PCR and Western blotting showed that StAR expression, both mRNA and protein, was markedly lower in regenerating adrenals than in the intact gland of sham-operated rats. Neither MG115 nor MG132 affected StAR expression in regenerating gland. Inhibitors induced a slight decrease in the plasma concentrations of aldosterone and corticosterone, but did not significantly alter metaphase index of the regenerating adrenal cortex. Our findings provide the first evidence that down-regulation of StAR occurs during the early stages of adrenal regeneration. Moreover, this suggests that the steroidogenic pathway is more sensitive to proteasome inhibitors than that regulating proliferative activity of regenerating adrenal cortex in the rat.

Cerebellin in the rat adrenal gland: gene expression and effects of CER and [des-Ser1]CER on the secretion and growth of cultured adrenocortical cells

Cerebellin (CER) is a regulatory peptide, originally isolated from rat cerebellum, which derives from the cleavage of precerebellin (Cbln), three types of which (Cbln1-3) have been identified in humans and rats. CER is also expressed in several extra-cerebellar tissues, including adrenal gland, and evidence has been provided that CER exerts a modulatory action on human and rat adrenal gland. Hence, we have investigated the expression of Cbln1-3 mRNAs and CER protein-immunoreactivity (IR) in the various zones of rat adrenal glands, and the effects of CER and its metabolite [des-Ser(1)]CER (des-CER) on the secretion and growth of cultured rat adrenocortical cells. Reverse transcription-polymerase chain reaction showed high and low expression of Cbln2 mRNA in zona glomerulosa (ZG) and zona fasciculata-reticularis, respectively. Cbln1 was not expressed, and Cbln3 mRNA was detected only in ZG. No Cbln expression was found in adrenal medulla. Immunocytochemistry demonstrated the presence of CER-IR exclusively in the adrenal cortex, the reaction being more intense in ZG. As expected, ACTH (10(-8) M) markedly enhanced corticosterone secretion and lowered proliferation rate of cultured adrenocortical cells. CER was ineffective, while des-CER exerted an ACTH-like effect, but only at the lowest concentration (10(-10) M). Taken together, these findings allow us to conclude that CER is expressed in rat adrenal cortex, and to suggest that CER conversion to des-CER by endopeptidases is needed for CER to exert its autocrine-paracrine regulatory functions.

Effects of leptin and leptin fragments on corticosterone secretion and growth of cultured rat adrenocortical cells

Compelling evidence indicates that leptin, acting via specific receptors (Ob-Ra and Ob-Rb) modulates adrenocortical-cell secretion. However, the results are controversial, inasmuch as either secretagogue or antisecretagogue effects have been reported. Hence, we decided to study the effects of a 96-h incubation with leptin and leptin fragments 116-130, 150-167, 138-167, 93-105, 22-56 and 26-39 (10(-8) and 10(-6) M) on the secretion and growth of cultured rat adrenocortical cells. Reverse transcription-polymerase chain reaction showed that control cultures expressed both Ob-Ra and Ob-Rb isoforms. As expected, ACTH (10(-8) M) raised corticosterone secretion and lowered proliferation rate of cultured cells. Native leptin elicited ACTH-like effects, while fragment 116-130 was ineffective. Leptin fragments 150-167 and 26-39 stimulated corticosterone production, and fragments 138-167 and 22-56 inhibited it. Fragment 93-105 exerted a dose-dependent biphasic effect on corticosterone secretion (i.e. stimulation and inhibition at the concentration of 10(-8) and 10(-6) M, respectively). Leptin fragment 26-39 enhanced proliferation of cultured cells, while fragments 138-167 and 22-56 were ineffective. Fragments 150-167 and 93-105 displayed proliferogenic and antiproliferogenic effects at the concentration of 10(-8) and 10(-6) M, respectively. Taken together, these findings allows us to conclude that native leptin and its fragments interact differently with Ob-Rs or interact with different Ob-R isoforms, thereby variously modulating secretion and growth of cultured rat adrenocortical cells.

Daily Changes of Plasma Corticosterone by an 8-h Daytime Feeding Occur Without Body Weight Loss or Severe Food Restriction in the Rat

Different studies have reported that daytime feeding entrains the circadian rhythm of corticosterone secretion in rats. However, it remained unclear whether calorie restriction or daytime feeding access have an effect. The aim of our study is to evaluate the effect of an 8-h daytime feeding access on the circadian rhythm of plasma corticosterone. Eleven adult male Wistar rats were assigned to two different conditions of access to food: ad lib feeding for one week and daytime feeding for the following two weeks. On the 7th, 14th and 21st day, blood samples were collected every 4 h from 08:00 to 04:00. Food intake and body weight were recorded daily. During daytime feeding, rats ingested 88% of the amount of food ingested over 24 h in the ad lib feeding period. However, body weight increased significantly from the first day to the end of experiment. Peak plasma corticosterone was 12 h shifted during daytime feeding period compared to the ad lib condition. This study showed that an 8-h daytime feeding entrained the circadian rhythm of plasma corticosterone without body weight loss or severe food restriction.

Irreversible Binding and Adrenocorticolytic Activity of the DDT Metabolite 3-Methylsulfonyl-DDE Examined in Tissue-Slice Culture

The persistent adrenocorticolytic DDT metabolite 3-methylsulfonyl-DDE (MeSO(2)-DDE) was originally identified in Baltic grey seals, a population suffering from adrenocortical hyperplasia. In mice, MeSO(2)-DDE induces mitochondrial degeneration and cellular necrosis in the adrenal zona fasciculata. In this study, we used precision-cut tissue slice culture to examine local CYP11B1-catalyzed irreversible binding of MeSO(2)-DDE in the murine adrenal cortex. We also examined effects on steroid hormone secretion, histology, and ultrastructure. As determined by microautoradiography, selective binding occurred in zona fasciculata of slices exposed to MeSO(2)-[(14)C]-DDE. Quantification of binding by phosphorautoradiography revealed a 3-fold reduction of binding in slices co-exposed to the CYP11B1 inhibitor metyrapone. As measured by HPLC, corticosterone and 11-deoxycorticosterone secretion to the medium increased linearly for at least 24 hr. Addition of the ACTH analog tetracosactide caused an 8-fold increase in corticosterone secretion. Addition of metyrapone reduced corticosterone secretion 4-fold. Exposure of slices to MeSO(2)-DDE (50 microM) reduced the rate of corticosterone secretion by 90% after 24 hr of incubation. As determined by electron microscopy, vacuolated mitochondria were present in zona fasciculata of slices exposed to MeSO(2)-DDE (50 microM) for 24 hr. Our findings show that all effects of MeSO(2)-DDE previously reported in vivo could be reproduced in adrenal slice culture ex vivo. This test system allows analysis of zone-specific irreversible binding and effects on steroid hormone secretion and target cell ultrastructure. We propose adrenal slice culture as a simple ex vivo test system with which to examine the adrenocorticolytic activity of xenobiotics in human and wild animal tissue.

Irreversible binding and adrenocorticolytic activity of the DDT metabolite 3-methylsulfonyl-DDE examined in tissue-slice culture.

The persistent adrenocorticolytic DDT metabolite 3-methylsulfonyl-DDE (MeSO(2)-DDE) was originally identified in Baltic grey seals, a population suffering from adrenocortical hyperplasia. In mice, MeSO(2)-DDE induces mitochondrial degeneration and cellular necrosis in the adrenal zona fasciculata. In this study, we used precision-cut tissue slice culture to examine local CYP11B1-catalyzed irreversible binding of MeSO(2)-DDE in the murine adrenal cortex. We also examined effects on steroid hormone secretion, histology, and ultrastructure. As determined by microautoradiography, selective binding occurred in zona fasciculata of slices exposed to MeSO(2)-[(14)C]-DDE. Quantification of binding by phosphorautoradiography revealed a 3-fold reduction of binding in slices co-exposed to the CYP11B1 inhibitor metyrapone. As measured by HPLC, corticosterone and 11-deoxycorticosterone secretion to the medium increased linearly for at least 24 hr. Addition of the ACTH analog tetracosactide caused an 8-fold increase in corticosterone secretion. Addition of metyrapone reduced corticosterone secretion 4-fold. Exposure of slices to MeSO(2)-DDE (50 microM) reduced the rate of corticosterone secretion by 90% after 24 hr of incubation. As determined by electron microscopy, vacuolated mitochondria were present in zona fasciculata of slices exposed to MeSO(2)-DDE (50 microM) for 24 hr. Our findings show that all effects of MeSO(2)-DDE previously reported in vivo could be reproduced in adrenal slice culture ex vivo. This test system allows analysis of zone-specific irreversible binding and effects on steroid hormone secretion and target cell ultrastructure. We propose adrenal slice culture as a simple ex vivo test system with which to examine the adrenocorticolytic activity of xenobiotics in human and wild animal tissue.

Accelerative effect of olive oil on adrenal corticosterone secretion in rats loaded with single or repetitive immersion-restraint stress.

The present study was performed to clarify the effects of dietary oils on physiological and metabolic changes induced by a stress, using one-time or repetitive water-immersion of restrained rats (single or repetitive stress) as an experimental stress load. In rats fed any test diets containing 20%) of the mixture of tripalmitin, tristearin, and corn oil (PSC), olive oil (OLI). safflower oil (SAF), and linseed oil (LIS) with repetitive stress loading, body weight gains and food intakes were generally reduced. The weights of the thymus and spleen also declined, but the adrenal weights were enhanced. Particularly, the increase in the adrenal weight of rats given the OLI diet was greater than of rats supplied with other diets. When the rats were loaded with the single or repetitive stress, the concentrations of urea, lipid peroxide, and corticosterone in the plasma were increased in rats fed any of dietary oils. The rise of plasma corticosterone level was especially great in rats fed the OLI diet. The concentrations of total cholesterol (T-CHOL) and triglyceride (TG) in the plasma and liver generally tended to be higher in rats fed the OLI diet than in rats given the other diets with and without stress exposure. Plasma corticosterone concentration was correlated to the adrenal weight (r=0.87, p<0.05). This study showed that OLI especially enhanced the adrenal weight in rats exposed to the repetitive stress and further raised the increased secretion of adrenal corticosterone in rats loaded with the single or repetitive stress compared with the other oils. The mechanism explaining these actions of OLI was inferred to be related to the levels of T-CHOL and TG in the plasma and liver generally enhanced by stress.

Frog chromaffin and adrenocortical cell co-cultures: a model for the study of medullary control of corticosteroidogenesis.

Phylogenetic, physiological and morphological evidence indicates that interactions between chromaffin and adrenocortical cells are involved in the differentiation and maintenance of function of both cell types. Chromaffin-adrenocortical interaction has become recognized as an important component of adrenocortical regulation; however, the mechanisms by which chromaffin cells modulate adrenocortical function are not well understood. To study directly chromaffin-adrenocortical cellular interactions, we developed primary frog (Rana pipiens) adrenal co-cultures. In these co-cultures, chromaffin cells extend processes that project towards or onto adrenocortical cells, mimicking their organization in vivo and indicating a potential for interaction between the two cell types. Cell survival and differentiation were optimized using a combination of NGF, FGF and histamine to enhance neurite outgrowth and fetal calf serum plus 10(-10) M ACTH to maintain steroidogenesis. Characterization of the cells by immunocytochemistry and histochemistry showed that chromaffin cells maintain expression of catecholamine biosynthetic enzymes and that adrenocortical cells maintain expression of steroidogenic enzymes. Furthermore, chromaffin cells release catecholamines upon stimulation with carbamylcholine or potassium while adrenocortical cells sustain a basal secretion rate of aldosterone and corticosterone that is augmented 10-40-fold by 0.1 nM to 10 nM ACTH. We therefore propose that these co-cultures serve as a useful model system to study the cellular and molecular mechanisms by which chromaffin cells modulate adrenocortical cell function.

Acidic fibroblast growth factor activates hypothalamic-pituitary-adrenocortical axis in rats

Effects of acidic fibroblast growth factor (aFGF), an endogenous satiety substance, on the hypothalamic-pituitary-adrenocortical axis were examined under pentobarbital sodium anesthesia in rats. A guide cannula was inserted into the cerebral third ventricle and a vascular indwelling catheter was inserted into the right atrium from the jugular vein 2 wk and 3 days, respectively, before the experiment. A marked dose-dependent increase in plasma corticosterone was detected from 20 min to 2 h after intracerebroventricular administration of aFGF (1-10 ng). Significant increases in plasma adrenocorticotropic hormone (ACTH) were observed from 5 to 150 min after the intracerebroventricular administration of 10 ng aFGF. Significant dose-dependent increases in plasma corticosterone were also observed after intravenous injections of aFGF (1, 10, and 100 ng), together with increases in the plasma ACTH level. Pretreatment with antibody to corticotropin-releasing factor via the intracerebroventricular route abolished the increases in corticosterone induced by intracerebroventricularly administered aFGF, but not those induced by intravenous injection of aFGF. In adrenal glands perfused in situ with artificial medium, the corticosterone secretion rate increased slightly in response to 10(-9) M aFGF. These findings suggest that intracerebroventricular administration of aFGF activates the hypothalamic-pituitary-adrenal axis via corticotropin-releasing factor release in the brain, whereas peripheral administration of aFGF activates adrenocortical secretion mainly via a direct action on ACTH release.

Release of ouabain-like compound (OLC) from the intact perfused rat adrenal gland

The present study was designed to investigate the effect of ACTH on release of OLC from the intact isolated rat adrenal, perfused in situ. OLC was measured by EIA. The limit of detection of the assay was 23 pmol/10minutes. Basal levels of OLC varied from 240 to <23 pmol/10min. Basal corticosterone levels were generally higher than OLC while aldosterone were generally lower. In 3 of the 5 perfusions the addition of ACTH was followed by rapid increases in both OLC and corticosterone secretion rates within 10 minutes of stimulation. Stimulated levels of OLC were 2 to 4-fold and of corticosterone were 3 to 7-fold those found in basal samples. OLC was found to co-elute with authentic ouabain under isocratic HPLC analysis whilst perfusion medium itself contained no detectable OLC immunoreactivity. These preliminary data suggest that the intact perfused rat adrenal preparation is a useful model for investigating the acute regulation of OLC secretion.

Sex-dependent peculiarities in the brain stem-regulated corticosterone secretion in rats

Iontophoretic administration of 6-hydroxydopamine into the area where catecholaminergic neurons of the dorsal vagal complex (A2 group) are located and loading with glucose induce sex-dependent differences in the corticosterone secretion in rats.