Investigations on the morphology and function of adrenocortical tissue regenerated from gland capsular fragments autotransplanted in the musculus gracilis of the rat

Involvement of DHH and GLI1 in adrenocortical autograft regeneration in rats

Bilateral adrenalectomy forces the patient to undergo glucocorticoid replacement therapy and bear a lifetime risk of adrenal crisis. Adrenal autotransplantation is considered useful to avoid adrenal crisis and glucocorticoid replacement therapy. However, the basic process of regeneration in adrenal autografts is poorly understood. Here, we investigated the essential regeneration factors in rat adrenocortical autografts, with a focus on the factors involved in adrenal development and steroidogenesis, such as Hh signalling. A remarkable renewal in cell proliferation and increase in Cyp11b1, which encodes 11-beta-hydroxylase, occurred in adrenocortical autografts from 2-3 weeks after autotransplantation. Serum corticosterone and adrenocorticotropic hormone levels were almost recovered to sham level at 4 weeks after autotransplantation. The adrenocortical autografts showed increased Dhh expression at 3 weeks after autotransplantation, but not Shh, which is the only Hh family member to have been reported to be expressed in the adrenal gland. Increased Gli1 expression was also found in the regenerated capsule at 3 weeks after autotransplantation. Dhh and Gli1 might function in concert to regenerate adrenocortical autografts. This is the first report to clearly show Dhh expression and its elevation in the adrenal gland.

Free and Microencapsulated Adrenal Cortical Cells Produce Similar Cortisol Responses When Stimulated by Acth: An in vitro study

Transplantation of endocrine cells, especially when protected from immune destruction, is an attractive alternative to whole organ transplantation. The current treatment for adrenal insufficiency whether congenital or acquired is hormone replacement, which is not considered fully physiological. In this study, we isolated porcine adrenal cortical cells by collagenase digestion. The cells were microencapsulated in alginate-polylysine-alginate membranes using electrostatic droplet generator. In vitro, ACTH stimulation of both free and microencapsulated adrenal cortical cells produced comparable cortisol response. It can be concluded that the microencapsulation process is not injurious to the adrenal cortical cells and that it does not hamper their secretory function.

Hypothalamo‑hypophysial system in rats with autotransplantation of the adrenal cortex

Patients with bilateral pheochromocytoma often require an adrenalectomy. Autotransplantation of the adrenal cortex is an alternative therapy that could potentially be performed instead of receiving glucocorticoid replacement following adrenalectomy. Adrenal cortex autotransplantation aims to avoid the side effects of long‑term steroid treatment and adrenal insufficiency. Although the function of the hypothalamo‑hypophysial system is critical for patients who have undergone adrenal cortex autotransplantation, the details of that system, with the exception of adrenocorticotropic hormone in the subjects with adrenal autotransplantation, have been overlooked for a long time. To clarify the precise effect of adrenal autotransplantation on the pituitary gland and hypothalamus, the current study examined the gene expression of hormones produced from the hypothalamus and pituitary gland. Bilateral adrenalectomy and adrenal autotransplantation were performed in 8 to 9‑week‑old male rats. The hypothalamus and pituitary tissues were collected at 4 weeks after surgery. Transcriptional regulation of hypothalamic and pituitary hormones was subsequently examined by reverse transcription‑quantitative polymerase chain reaction. Proopiomelanocortin, glycoprotein hormone α polypeptide, and thyroid stimulating hormone β were significantly elevated in the pituitary gland of autotransplanted rats when compared with sham‑operated rats. In addition, there were significant differences in the levels of corticotropin releasing hormone receptor 1 (Crhr1), Crhr2, nuclear receptor subfamily 3 group C member 1 and thyrotropin releasing hormone receptor between the sham‑operated rats and autotransplanted rats in the pituitary gland. In the hypothalamus, corticotropin releasing hormone and urocortin 2 mRNA was significantly upregulated in autotransplanted rats compared with sham‑operated rats. The authors identified significant alterations in the function of not only the hypothalamus‑pituitary‑adrenal axis, but also the adenohypophysis thyrotropes in autotransplanted rats. In the future, it will be important to examine other tissues affected by glucocorticoids following adrenal cortex autotransplantation.

Functional zonation of the rat adrenal cortex: the development and maintenance

The adrenal cortex of mammals consists of three concentric zones, i.e., the zona glomerulosa (zG), the zona fasciculata (zF), and the zona reticularis (zR), which secrete mineralocorticoids, glucocorticoids, and adrenal androgens, respectively. In 1994, we identified immunohistochemically a new zone between zG and zF of the rat adrenal gland. The zone appeared to be devoid of any significant endocrine functions specific to adrenocortical zones, therefore, we designated the zone as "undifferentiated cell zone (zU)". Further, BrdU (5-bromo-2'-deoxyuridine)-incorporating cells (cells in S-phase) were concentrated at the outer region and the inner region of zU, and these cells proliferated and migrated bidirectionally: toward zG centrifugally and toward zF centripetally. We proposed that cells in and around zU are stem/progenitor cells of the rat adrenal cortex, maintaining functional zonation of the adrenal cortex. The view is consistent with observations reported recently that Sonic hedgehog (Shh), an important factor in embryonic development and adult stem cell maintenance, exists in zU of the rat adrenal gland and the Shh-containing cells seem to migrate bidirectionally.

Adrenal extracellular matrix scaffolds support adrenocortical cell proliferation and function in vitro

Transplantation of functional adrenal cortex cells could reduce morbidity and increase the quality of life of patients with adrenal insufficiency. Our aim was to determine whether adrenal extracellular matrix (ECM) scaffolds promote adrenocortical cell endocrine function and proliferation in vitro. We seeded decellularized porcine adrenal ECM with primary human fetal adrenocortical (HFA) cells. Adrenocortical function was quantified by cortisol secretion of HFA-ECM constructs after stimulation with adrenocorticotropic hormone. Proliferation was assessed by adenosine triphosphate assay. HFA-ECM construct morphology was evaluated by immunofluorescence microscopy and scanning electron microscopy. Adrenal HFA-ECM constructs coated with laminin were compared to uncoated constructs. Laminin coating did not significantly affect HFA morphology, proliferation, or function. We demonstrated HFA cell attachment to adrenal ECM scaffolds. Cortisol production and HFA cell proliferation were significantly increased in HFA-ECM constructs compared to controls (p < 0.05), and cortisol secretion rate per cell is comparable to that of human adult and fetal explants. We conclude that adrenal ECM supports endocrine function and proliferation of adrenocortical cells in vitro. Adrenal ECM scaffolds may form the basis for biocompatible tissue-engineered adrenal replacements.

Expression of the zinc-finger transcription factor Snail in adrenocortical carcinoma is associated with decreased survival

In this study, we evaluate whether Snail is expressed in adrenocortical cancer (ACC) and if its expression is related to patient outcome. One of the best known functions of the zinc-finger transcription factor Snail is to induce epithelial-to-mesenchymal transition (EMT). Increasing evidence suggests that EMT plays a pivotal role in tumour progression and metastatic spread. Snail and E-cadherin expression were assessed by immunohistochemistry in 26 resected ACCs and real-time quantitative RT–PCR expression analysis was performed. Data were correlated with clinical outcome and in particular with overall patient survival. Seventeen of 26 (65%) ACC tumour samples expressed Snail when assessed by immunohistochemistry. Snail expression was neither detected in normal adrenocortical tissue, nor in benign adrenocortical adenomas. Expression levels were confirmed on the mRNA level by Real-Time–PCR. Survival rates were significantly decreased in Snail-positive tumours compared to Snail-negative tumours: 10 out of 16 vs one out of eight patients succumbed to disease after a median follow up of 14.5 and 28.5 months, respectively (P=0.03). Patients with Snail-expressing ACCs presented in advanced disease (11 out of 12 vs 6 out of 14, P=0.01) and tend to develop distant metastases more frequently than patients with negative staining (7 out of 11 vs two out of eight, P=0.19). In conclusion, we describe for the first time that Snail is expressed in a large subset of ACCs. Furthermore, Snail expression is associated with decreased survival, advanced disease and higher risk of developing distant metastases.

Addisonian crisis and tuberculous epididymo-orchitis

OBJECTIVE

To describe a case of acute primary adrenal insufficiency in which tuberculosis was subsequently detected as the etiologic factor when the patient presented with tuberculous epididymo-orchitis.

METHODS

A case of acute primary adrenal insufficiency associated with bilaterally enlarged adrenal glands is reported, along with the subsequent finding of a scrotal mass diagnosed as tuberculous epididymo-orchitis. Diagnosis, adrenal function, and results of imaging studies after institution of antituberculous treatment are discussed.

RESULTS

A 41-year-old Egyptian man, who had immigrated to the United States 5 years previously, had acute psychosis and addisonian crisis. A substantially increased early morning level of plasma adrenocorticotropic hormone and a low level of serum cortisol confirmed the diagnosis of primary adrenal insufficiency. Both adrenal glands were enlarged but without calcification on computed tomography. A previous bacille Calmette-Guérin vaccination complicated the interpretation of a positive tuberculin skin test result. Both lungs were clear on chest radiography and computed tomography. Seven months later, the patient had a left scrotal mass and underwent radical orchiectomy. Examination of the pathology specimen showed caseous granulomatous inflammation and necrosis, and acid-fast bacilli were identified. Culture was positive for Mycobacterium tuberculosis.

CONCLUSION

In a patient from a country where tuberculosis is endemic, tuberculosis should be considered in the differential diagnosis when primary adrenal insufficiency is detected, especially in association with enlarged or calcified adrenal glands. Extra-adrenal tuberculous involvement should be actively sought because it may provide indirect microbiologic or histologic clues. Other than the lungs, special attention should be paid to the genitourinary system.

The role of corticosterone in the metabolic recovery after intrasplenic adrenal autotransplantation in rats

Transplantation of adrenal cortical tissue may represent an alternative treatment to reestablish glucocorticoid secretion in adrenal insufficiency. In the present work, performed in adrenalectomized rats and adrenalectomized rats with a complete autotransplanted adrenal into the spleen, several hormones and biochemical parameters were measured and compared to control animals, in order to examine hormone interactions. Rats were sacrificed three weeks after surgery, and plasma and tissue samples were obtained for hormone and biochemical measurements. In adrenalectomized animals, plasma corticosterone, aldosterone and insulin levels were profoundly decreased, whereas in autotransplanted rats plasma corticosterone levels showed a partial recovery, aldosterone plasma concentrations remained low, and plasma insulin levels increased to values close to those of the controls. Both groups showed a marked elevation of plasma ACTH levels, as well as significantly increased plasma glucagon concentrations. In autotransplanted animals, most of the biochemical parameters, which were altered in adrenalectomized rats, returned to normal levels. These results suggest that increased glucagon levels in adrenalectomized and autotransplanted animals, may contribute to the marked increase of plasma ACTH, and could also be important in the recovery of plasma glucose and hepatic glycogen observed in autografted rats. Since high glucagon concentrations alone were unable to normalize carbohydrate levels in adrenalectomized animals, it appears that glucagon can act only in the presence of corticosterone.

EXPRESSION OF VASCULAR ENDOTHELIAL GROWTH FACTOR AND ITS RECEPTORS FLK-1 AND FLT-1 DURING THE REGENERATION OF AUTOTRANSPLANTED ADRENAL CORTEX IN THE ADRENALECTOMIZED RAT

PURPOSE

Autotransplantation of the adrenal cortex may be a therapeutic alternative in the future. For successful adrenal transplantation revascularization is necessary. It is possible that vascular endothelial growth factor (VEGF), which is a potent angiogenic peptide, may have some roles in adrenal transplantation through 2 its receptors, kinase insert domain-containing region (Flk-1) and fms-like tyrosine kinase (Flt-1). Therefore, we studied sequential changes in expression of VEGF, Flk-1 and Flt-1 in regenerated adrenal.

MATERIALS AND METHODS

Eight to 9-week-old male Wistar rats underwent bilateral adrenalectomy and immediate adrenal capsular autotransplantation. The expression of VEGF, Flk-1 and Flt-1 was analyzed by immunohistochemistry and reverse-transcriptase-polymerase chain reaction.

RESULTS

Angiogenesis was observed in the remodeling of adrenal sinusoidal endothelium during adrenal regeneration. Reverse transcriptase-polymerase chain reaction and immunohistochemistry showed that VEGF expression increased in grafted tissue with time after transplantation and its Flk-1 receptor, which localized to endothelial cells, increased transiently during the regeneration process. Immunostaining for Flt-1 receptor was identified in adrenocortical cells and its intensity gradually increased during adrenal regeneration.

CONCLUSIONS

During adrenal gland regeneration VEGF and its receptors Flk-1 and Flt-1 are thought to be involved in neovascularization.

Proliferation of capsular stem cells induced by ACTH in the rat adrenal cortex

Despite great efforts devoted to clarifying the localization of proliferative activity in the adrenal cortex, the agents that stimulate proliferation remain controversial, and the nature of the stem cells from which cortical cells differentiate is incompletely understood. We studied proliferative activity in the rat adrenal cortex using an immunohistochemical method to detect the presence of the Proliferating Cell Nuclear Antigen (PCNA) (an intranuclear enzyme whose synthesis reaches the maximum intensity during the S-phase of the cell cycle). Groups of six rats were subjected to daily intraperitoneal injection of either corticotropin (ACTH1-24--0.2 mg/kg), dexamethasone (Dexa--4 mg/kg) or 0.9% saline for three consecutive days and killed 24 h after the last injection. Adrenal weight was significantly increased by ACTH treatment and reduced by Dexa. Concentrations of endogenous ACTH in plasma were lower in the Dexa group than in controls, and curiously, this was true in the ACTH1-24 treated group as well, probably in consequence of the increased corticosterone levels providing negative feedback at the hypothalamic-pituitary level. Corticosterone levels, as expected, were increased by the ACTH stimulus and reduced by the use of Dexa. Proliferating cell nuclear antigen immunostaining was close to zero in Dexa treated animals and low in controls. In ACTH treated rats, a significantly increased number of cells were positively stained. Positive cells were identified in both in zona glomerulosa (ZG) and zona intermedia (ZI) but many were located in the capsule. Zona fasciculata (ZF) and zona reticularis (ZR) were devoid of staining in all of these cases. We conclude that pharmacological doses of ACTH induce proliferation of capsular fibroblasts. Following descriptions by early 20th century researchers it is possible that these cells may also be stem cells and differentiate into adrenal cortex cells.

Rat adrenal transplants are reinnervated: an invalid model of denervated adrenal cortical tissue

Adrenal autotransplantation is a widely used approach to investigate the potential for neural modulation of adrenal cortical function. It is believed that regenerating adrenal transplants are not reinnervated, thereby providing a model to investigate adrenal function in the absence of neural modulation. However, the hypothesis that adrenal transplants become reinnervated has not been directly tested. The purpose of the present study was to characterize the time course, extent, and nature of the reinnervation of the regenerating adrenal transplant and to assess whether the recovery of steroidogenic function and enzyme expression correlates temporally with the presence of innervation. Using immunohistofluorescent detection of tyrosine hydroxylase (TH), neuropeptide Y (NPY), calcitonin gene-related peptide (CGRP), and vasoactive intestinal peptide (VIP), the innervation of regenerating adrenals was assessed 14-30 days after transplantation of adrenal capsules beneath the kidney capsule in rats. Extensive reinnervation by TH-, NPY-, and VIP-positive fibres was present by 14 days after transplantation including regions of the adrenal capsule and cortex, with only minimal reinnervation by CGRP-positive fibres up to 30 days. TH- and NPY-positive chromaffin cells were also observed in the regenerating transplants. In addition, there was marked recovery of steroidogenic function and steroidogenic enzyme expression up to 30 days. The finding that nerve fibres are present in the transplants during the re-establishment of steroidogenic function and enzyme expression suggests that innervation may modulate the regeneration and functional recovery of adrenal transplants. In an attempt to prevent reinnervation of transplants, adrenal capsules were autotransplanted to denervated kidneys. Immunohistochemical analysis showed that, despite extensive denervation of the kidney tissue, the reinnervation and regeneration of the adrenal transplants still occurred. These data demonstrate the marked capacity of the regenerating adrenal to become reinnervated and reinforces the conclusion that adrenal transplants are an invalid model of denervated adrenal cortical tissue.

Transplantation of H-2Kb-transgenic adrenocortical cells in the mouse having undergone an adrenalectomy: functional and morphological aspects

BACKGROUND

A new model of cellular adrenocortical transplantation after bilateral adrenalectomy in the mouse was established. This model was used to study the effects of the expression of the transgenic MHC class I molecule H-2K(b) (Kb) on graft survival and morphologic features, corticosterone secretion, and the possibility of tolerance induction in the recipient.

METHOD

A single cell suspension of purified adrenocortical cells was grafted under the kidney capsule of B10.Br (H-2k) mice having adrenalectomies. Syngeneic, fully MHC-mismatched, and MHC class I-incompatible Kb-transgenic mice served as donor strains. To analyze graft function, urinary excretion and serum levels of corticosterone were monitored over 100 days. Tolerance induction in the graft recipients of Kb-transgenic and third party skin grafts was tested on day 50 after adrenocortical transplantation. Histological sections of the adrenocortical grafts were obtained on day 100.

RESULTS

Recipients of syngeneic and Kb-transgenic grafts displayed pretransplant corticosterone levels on days 20, 50, and 100 and ACTH-stimulated serum corticosterone levels similar to those of controls on day 100 after adrenocortical transplantation. In contrast, in recipients of fully MHC-mismatched grafts, corticosterone excretion was significantly reduced. In this group, 4 of 7 mice did not survive. Syngeneic skin grafts survived indefinitely in recipients of syngeneic and Kb-transgenic adrenocortical grafts, whereas Kb-transgenic and fully MHC-mismatched skin grafts were acutely rejected. Tissue sections of the adrenocortical grafts revealed vascularized cell conglomerates in syngeneic and Kb-transgenic grafts without infiltrations of mononuclear cells. Furthermore, a differentiation similar to adrenocortical organization was partly found.

CONCLUSION

In conclusion, a model of cellular adrenocortical transplantation was established. The results show that syngeneic transplantation resulted in physiological corticosterone levels early after transplantation, whereas fully MHC-incompatible grafts were rejected. Recipients of Kb-transgenic grafts showed unimpaired adrenocortical function, but did not tolerize toward Kb-transgenic skin grafts. Possible mechanisms include a local immunomodulatory effect of glucocorticoids secreted by the graft and a low immunogenicity of the relatively small numbers of transplanted cells.

Immune-endocrine interactions in the mammalian adrenal gland: facts and hypotheses

Several cytokines, which are the major mediators of the inflammatory responses, are well-known to stimulate the hypothalamopituitary corticotropin-releasing hormone (CRH)/adrenocorticotropic hormone (ACTH) system, thereby evoking secretory responses by the adrenal cortex. Many of these cytokines, including interleukin-1 (IL-1), IL-2, IL-6, tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (INF-gamma) are synthesized in the adrenal gland by both parenchymal cells and resident macrophages, and the release of some of them (e.g., IL-6 and TNF-alpha) is regulated by the main agonists of steroid hormone secretion (e.g., ACTH and angiotensin-II) and bacterial endotoxins. Adrenocortical and adrenomedullary cells are provided with specific receptors for IL-1, IL-2, and IL-6. IL-1 and TNF-alpha directly inhibit aldosterone secretion of zona glomerulosa cells, whereas IL-6 enhances it. IL-2, IL-3, IL-6, and INF-alpha are able to directly stimulate glucocorticoid production by zona fasciculata and zona reticularis cells, whereas IL-1 exerts an analogous effect through an indirect mechanism involving the stimulation of catecholamine release by chromaffin cells and/or the activation of the intramedullary CRH/ACTH system; again, TNF-alpha depresses glucocorticoid synthesis. IL-6 raises androgen secretion by inner adrenocortical layers. IL-1 enhances the proliferation of adrenocortical cells, and findings suggest that cytokines may control the apoptotic deletion of senescent zona reticularis cells. The relevance of the intraadrenal cytokine system in the fine-tuning of the secretion and growth of the adrenal cortex under normal conditions remains to be explored. However, indirect proof is available that local immune-endocrine interactions may play an important role in modulating adrenal responses to inflammatory and immune challenges and stresses.

Distribution and functional significance of angiotensin-II AT1- and AT2-receptor subtypes in the rat adrenal gland

The distribution and the functional significance of angiotensin-II (ANG-II) receptor subtypes, AT1 and AT2, in the rat adrenal gland has been investigated in vitro. Autoradiographic assessment of the selective displacement of [125I]ANG-II binding by selective ligands of the two receptor subtypes indicated that zona glomerulosa (ZG) was provided with both AT1 and AT2, and adrenal medulla (AM) almost exclusively with AT2 receptors. ANG-II (10(-9) M) evoked a marked rise in the secretion of aldosterone by dispersed ZG cells and catecholamines by AM fragments. The selective AT1-receptor antagonist DuP753 blocked aldosterone response to ANG-II, while the selective AT2-receptor antagonist PD123319 was ineffective. Catecholamine response to ANG-II was inhibited by PD123319 and only moderately affected by high concentrations of DuP753. The selective AT2-receptor agonist CGP42112 did not change basal aldosterone release of ZG cells, but concentration-dependently enhanced basal catecholamine release by AM fragments. In light of these findings the conclusion is drawn that in the rat the aldosterone secretagogue effect of ANG-II is exclusively mediated by the AT1 receptors present in the ZG, while the catecholamine secretagogue action preminently involves the activation of AT2 receptor located on medullary chromaffin cells.

Fetal adrenal transplantation: success of a laparoscopic technique in rats

BACKGROUND/PURPOSE

The present study investigates a new laparoscopic technique for fetal adrenal transplantation in rats.

RESULTS

The procedure was successful in 9 of 10 cases (one hole in the omentum) with no postoperative complications. On examination 4 weeks postoperatively, all but one graft showed macroscopic integrity, vascular supply, and histological maturation to normal zonal differentiation. When bilateral adrenalectomy was performed in the recipient to assess endocrine competence of the fetal adrenal grafts, survival was prolonged and Addison crisis was prevented in the animals that underwent transplantation. Levels of aldosterone dropped within the first week after adrenalectomy, but recovered steadily. Analysis of corticosterone demonstrated that levels fell to 25% of sham operated rats in the first week, but then steadily climbed to 70%.

CONCLUSIONS

To the authors' knowledge this report presents the first study for laparoscopic transplantation of fetal tissues. Laparoscopic transplantation of fetal adrenal glands seemed feasible and successful in rats. The fetal adrenal transplants matured and served for a prolonged survival.

Morphological and functional studies of the paracrine interaction between cortex and medulla in the adrenal gland

Within the last years it has become evident that besides the hypothalamo-pituitary-adrenal axis, extrapituitary mechanisms exist that regulate the activity of the adrenal cortex. In this context, intra-adrenal regulatory mechanisms play an important role. Several secretory products from adrenomedullary cells are able to influence adrenocortical steroidogenesis. Since the main blood flow within the adrenal is directed centripetally from the cortex to the medulla, chromatin cells should act on cortical cells in a paracrine manner. The morphological prerequisite for this regulatory pathway is seen in the close apposition of the two tissues. Within the mammalian adrenal, the two endocrine tissues are interwoven to an astonishing degree with cortical cells located within the medulla and vice versa. It is concluded from morphological and functional studies that paracrine interactions between cortex and medulla play an important role in the regulation of adrenocortical steroidogenesis.

Modulation of autotransplanted adrenal gland by endothelin-1: a morphological and biochemical study

BACKGROUND

Adrenal gland autotransplantation, a model of cortical tissue regeneration, provides the reconstruction of distinct functional and morphological zonae. A morphological and biochemical study of the adrenal gland of adult male rats after autotransplantation and endothelin-1 (ET-1) administration was made.

METHODS

The technique involved bilateral adrenalectomy and placement of pieces of the adrenal gland in a dorsal plane between the skin and muscle. The animals were killed 90 days after the autotransplantation and 1 hr after intravenous ET-1 administration (0.5 microgram/kg body weight). The autotransplanted pieces were removed, fixed, and processed for light and electron microscopic morphologic studies. Trunk blood was collected for steroid assay.

RESULTS

Saline-treated control autotransplanted animals showed no remarkable differences in adrenal organization; grafts exhibiting a mass of regenerated cortical tissue were arranged in nests of glandular cells surrounded by a fibrous capsule and intersected by layers of connective tissue. The adrenal medulla was systematically absent. Ultrastructure of ET-1-treated animals revealed an inner area in the graft, consisting mainly of fasciculatalike cells. Cytoplasmic changes were evident, with high variations in mitochondrial size and arrangement. Profiles of smooth endoplasmic reticulum sometimes exhibited evidence of hypertrophy. Glandular cells in the graft outer area (subcapsular) were almost invariably like glomerulosa; however, some of them showed mitochondria with a peculiar arrangement of the cristae. "Hybrid" cells with mitochondria resembling those of the zona reticularis were also observed in the subcapsular environment. ET-1-stimulated animals showed significant increases in plasma corticosterone and aldosterone concentrations.

CONCLUSIONS

Endothelin-1, previously reported to stimulate acutely the aldosterone secretion by the adrenal zona glomerulosa in the rat, seems to exert a modulator role on the physiology of adrenal autotransplants, their regeneration and secretion.

Further investigations on the effects of neuropeptide Y on the secretion and growth of rat adrenal zona glomerulosa

NPY is a regulatory peptide, high levels of which are contained in adrenal glands of several mammals and which is co-released with catecholamines during various stressful conditions. The acute and chronic effects of NPY on adrenocortical secretion and growth were studied in the rat. NPY concentration-dependently increased aldosterone (ALDO), but not corticosterone (B) secretion of adrenal slices (maximal effective concentration was 10(-7) M). Two competitive inhibitors of NPY receptors, named PYX-1 and PYX-2, were found to dose-dependently inhibit ALDO response of adrenal preparations to 10(-7) M NPY; PYX-2 was more efficient than PYX-1, and at a concentration of 10(-5) M completely annulled the effect of 10(-7) M NPY. The acute bolus intraperitoneal (i.p.) injection of NPY (3 nmol/kg) raised plasma ALDO concentration (PAC), but not that of B (PBC); this effect of NPY was blocked by the simultaneous injection of PYX-2 (300 nmol/kg). The prolonged i.p. infusion with NPY (3 nmol/kg/h for 7 days) increased PAC (but not PBC) and induced a marked hypertrophy of the zona glomerulosa (ZG) and its parenchymal cells; dispersed ZG cells obtained from NPY-infused rats displayed a significantly enhanced basal and maximally agonist-stimulated ALDO production. The simultaneous infusion with PYX-2 (300 nmol/kg/h) completely annulled all these effects of NPY. The acute or chronic administration of PYX-2 alone did not evoke any apparent effect on the ZG secretion and growth. In light of these findings the following conclusions can be drawn: (i) NPY is able to stimulate not only the secretion, but also the growth of adrenal ZG in rats, via a receptor-mediated mechanism (since this effect is blocked by PYX-2); (ii) endogenous NPY does not play a prominent role in the physiological maintenance of secretion and growth of rat ZG (since PYX-2 alone is ineffective); (iii) NPY may play a crucial role in the fine tuning of the ZG functions in conditions requiring an increased release of mineralocorticoid hormones.

Study of ACTH-immunoreactive cells after transplantation of neonatal adrenal glands into adult adrenalectomized rats

The morphological and morphometrical features of the ACTH-immunoreactive cells of the anterior pituitary gland were compared between adult rats with intact adrenals, adult rats without adrenals, and adult rats with regenerated adrenocortical nodules. The removal of the adrenal glands produced a great increase in the number and size of the cytoplasmic processes of the ACTH-immunoreactive cells that sometimes establish contact with those of the neighbouring immunoreactive cells. In addition, in this experimental group, the ACTH-cell percentage and the mean cell, cytoplasmic, and nuclear areas were greatly increased in comparison with those found in control animals. Several regenerated adrenocortical nodules were observed in the small-bowel segment of rats transplanted with neonatal adrenal glands. The percentage and morphometrical values of the pituitary ACTH-reactive cells of this experimental group, although slightly increased relative to the rats with intact adrenals, were greatly decreased in relation to those of the adrenalectomized animals. It is concluded that the neonatal adrenal tissue regenerated after its transplantation into adult rats, a process that modified the percentage, the morphological characteristics, and the morphometrical values of the ACTH-immunoreactive cells of the adrenalectomized rats.

Adrenal medulla is involved in the aldosterone secretagogue effect of substance P

Substance P (SP) increased aldosterone secretion of rat adrenal slices, but not of isolated zona glomerulosa cells, and this effect was annulled by two specific antagonist of SP (SP-A). Both tissue preparations displayed an aldosterone secretory response to isoprenaline (IP) that was blocked by l-alprenolol (AL). AL reversed the aldosterone response of adrenal slices to IP, SP, or IP plus SP, whereas SP-A only suppressed that to SP. Quarters of adrenocortical autotransplants, which are completely deprived of chromaffin cells, showed an aldosterone response to IP, but not to SP. These findings suggest that the mechanism underlying the aldosterone secretagogue action of SP probably involves the stimulation of catecholamine release by adrenal medulla chromaffin cells.

Effects of neuromedin U-8 on the secretory activity of the rat adrenal cortex: evidence for an indirect action requiring the presence of the zona medullaris

The acute effect of increasing concentrations (from 10(-8) to 10(-6) M) of neuromedin U-8 (NMU-8) on steroid secretion of rat adrenal gland was investigated in vitro by high-pressure liquid chromatography. The production of the following steroids was measured: pregnenolone (PREG), progesterone (PROG), 11-deoxycorticosterone (DOC), corticosterone (B), 18-hydroxy-11-deoxycorticosterone (18OH-DOC), 18-hydroxycorticosterone (18OH-B) and aldosterone (ALDO). NMU-8 had no effects on either dispersed adrenocortical cells or fragments of adrenocortical autotransplants lacking medullary chromaffin cells. Conversely, NMU-8 exerted concentration-dependent secretagogue effects on adrenal slices, including both cortex and medulla. At all concentrations tested, NMU-8 increased the production of both PREG and total post-PREG steroids. The increase in total post-PREG steroid output induced by low concentrations of NMU-8 (10(-8) M) was due to similar rises in the production of non-18-hydroxylated steroids (PROG, DOC and B) and 18-hydroxylated hormones (18OH-DOC, 18OH-B and ALDO); conversely, that provoked by higher concentrations of the neuropeptide (10(-7) to 10(-6) M) was almost exclusively caused by the rise in the yield of 18-hydroxylated steroids. The stimulating effect of NMU-8 on PREG output was blocked by both alpha-helical-CRH and corticotropin-inhibiting peptide, which are competitive inhibitors of CRH and ACTH, respectively. The following conclusions have been drawn: (1) NMU-8 affects adrenal steroid secretion indirectly by acting on the medullary chromaffin cells, which in turn may paracrinally stimulate the cortical ones; (2) at all concentrations tested, NMU-8, by stimulating the intramedullary CRH/ACTH system, causes a net rise in the activity of the early rate-limiting step of steroidogenesis, with the consequent increase in the output of the entire spectrum of post-PREG steroids; and (3) at higher concentrations (over 10(-8) M), NMU-8 also elicits the release from chromaffin cells of a factor (not yet known) that specifically enhances 18-hydroxylase activity.

Evidence that endogenous vasoactive intestinal peptide (VIP) plays a role in the maintenance of the growth and steroidogenic capacity of rat adrenal zona glomerulosa

The effects of a 7-day intraperitoneal infusion with VIP (0.03 nmol.kg-1.min-1) and its antagonist [4-Cl-D-Phe6,Leu17]-VIP (VIP-A; 3 nmol.kg-1.min-1) were studied in sham and bilaterally adrenalectomized rats bearing ACTH and angiotensin II (ANG-II)-responsive adrenocortical autotransplants. VIP significantly increased plasma aldosterone (ALDO) concentration (PAC) and lowered plasma renin activity (PRA) in both groups of animals, without affecting plasma levels of ACTH and corticosterone. This treatment caused a marked hypertrophy of adrenal zona glomerulosa (ZG) and its parenchymal cells (without inducing any significant change in the zona-fasciculata morphology), as well as of ZG-like cells of autotransplants. Isolated ZG cells and autotransplant quarters obtained from VIP-infused rats evidenced a notable increase in both their basal and maximally ACTH- or ANG-II-stimulated ALDO secretion. The simultaneous infusion of rats with VIP-A completely reversed all these effects of VIP. The infusion with VIP-A alone caused, in sham-operated rats, a net decrease in PAC, coupled with a rise in PRA, and a marked atrophy of ZG and ZG cells; basal and maximally stimulated ALDO secretion of dispersed ZG cells was also significantly lowered. Conversely, VIP-A did not evoke any appreciable effect in autotransplanted rats. These findings suggest that endogenous VIP is specifically involved in the maintenance of the growth and secretory capacity of rat adrenal ZG. Since regenerated adrenocortical autotransplants, which are responsive to VIP but not to VIP-A infusion, are completely deprived of chromaffin cells, the hypothesis is advanced that adrenal medulla may be the source of endogenous VIP regulating ZG function.

Zona glomerulosa of the adrenal gland in a transgenic strain of rat: a morphologic and functional study

Transgenic rats for the murine Ren-2 gene display high blood pressure, low circulating levels of angiotensin II, and high renin content in the adrenal glands. Moreover, transgenic rats possess an increased aldosterone secretion (maximal from 6 to 18 weeks of age), paralleling the development of hypertension. To investigate further the cytophysiology of the adrenal glands of this strain of rats, we performed a combined morphometric and functional study of the zona glomerulosa of 10-week-old female transgenic rats. Morphometry did not reveal notable differences between zona glomerulosa cells of transgenic and age- and sex-matched Sprague-Dawley rats, with the exception of a marked accumulation of lipid droplets, in which cholesterol and cholesterol esters are stored. The volume of the lipid-droplet compartment underwent a significant decrease when transgenic rats were previously injected with angiotensin II or ACTH. Dispersed zona glomerulosa cells of transgenic rats showed a significantly higher basal aldosterone secretion, but their response to angiotensin II and ACTH was similar to that of Sprague-Dawley animals. Angiotensin II-receptor number and affinity were not dissimilar in zona glomerulosa cells of transgenic and Sprague-Dawley rats. These data suggest that the sustained stimulation of the adrenal renin-angiotensin system in transgenic animals causes an increase in the accumulation in zona glomerulosa cells of cholesterol available for steroidogenesis, as indicated by the expanded volume of the lipid-droplet compartment and the elevated basal steroidogenesis. However, the basal hyperfunction of the zona glomerulosa in transgenic animals does not appear to be coupled with an enhanced responsivity to its main secretagogues, at least in terms of aldosterone secretion.

The possible involvement of galanin in the modulation of the function of rat pituitary-adrenocortical axis under basal and stressful conditions

The effect of a s.c. bolus injection of 2 micrograms galanin on the hypothalamo-pituitary-adrenocortical (HPA) axis were investigated in both normal and ether-stressed (2 min ether-vapor inhalation) or cold-stressed (20 min at 4 degrees C) rats. Blood concentrations of ACTH, aldosterone (ALDO) and corticosterone (B) were measured by specific RIA, 1, 2 or 4 h after galanin injection. Galanin administration to normal rats resulted in a marked rise in the blood levels of ACTH, ALDO and B at 1h and 2 h, the values returned to the baseline after 4 h. Ether and cold stresses notably raised the blood levels of ACTH, ALDO and B, and these rises lasted unchanged until 4 h. Galanin markedly potentiated ACTH and ALDO responses to ether stress at 1 and 2 h, but B response remained unchanged. ACTH response to cold stress was not affected by galanin; however, galanin magnified ALDO response to cold stress at 4 h, and enhanced at 1 h and depressed at 2 h that of B. In light of these findings the following conclusions can be drawn: (i) galanin exerts a stimulatory effect on HPA axis of rats under basal conditions; (ii) under our experimental conditions, ether stress exerts a stronger stimulation of HPA axis than cold stress; (iii) the galaninergic mechanisms involved in the stimulation of ACTH release do not interfere with ether stress-activated ones controlling ACTH secretion, and are probably similar to those underlying the effect of cold stress; (iv) steroidogenic capacity of adrenal cortex, at least in term of glucocorticoid hormones, is a rate-limiting step in the response of rat HPA axis to severe stresses; and (v) galanin exerts a direct secretory action of the rat adrenal gland, that can manifest itself only in the case of submaximally cold stress-stimulated HPA axis.

Effects of cyclosporine-A on steroid secretion of dispersed rat adrenocortical cells

The acute effect of cyclosporine-A (CSA), a potent immunosuppressive agent, on the secretory activity of dispersed rat adrenocortical cells was investigated. The production of the following steroid hormones was assayed by high performance liquid chromatography: pregnenolone (PREG), progesterone (PROG), 11-deoxycorticosterone (DOC), corticosterone (B), 18-hydroxy-11-deoxycorticosterone (18OH-DOC), 18-hydroxycorticosterone (18OH-B) and aldosterone (ALDO); B and ALDO outputs were also measured by radioimmunoassay. Low concentrations of CSA (0.1-0.2 mg/ml) enhanced basal, but not ACTH- or angiotensin-II (ANG-II) 10(-8) M-stimulated, secretions of PREG, non-18-hydroxylated steroids (PROG, DOC and B) and 18-hydroxylated steroids (18OH-DOC, 18OH-B and ALDO) of both zona glomerulosa (ZG) and zonae fasciculata and reticularis (ZF/ZR) cells. Middle concentrations of CSA (from 0.3 to 0.5 mg/ml) did not affect PREG yield, nor did they alter basal and ACTH-stimulated post-PREG output of both ZG and ZF/ZR cells; however, they elicited a marked decrease in ANG-II-enhanced production of 18-hydroxylated steroid by AG cells. Concentrations of CSA higher than 0.5 mg/ml strikingly reduced either basal and agonist-stimulated over-all steroidogenesis of both ZG and ZF/ZR cells. These findings suggest that CSA at low concentrations strongly stimulates the conversion of cholesterol to PREG (i.e. the rate-limiting step of steroidogenesis), while at middle concentrations it did not affect this early step, but specifically interferes with the intracellular events which transduce the stimulatory signal of ANG-II on the late steps of mineralocorticoid production (i.e. the conversion of B to ALDO). At higher concentrations, CSA probably exerts a cytotoxic effect.

Evidence that endogenous somatostatin (SRIF) exerts an inhibitory control on the function and growth of rat adrenal zona glomerulosa. The possible involvement of zona medullaris as a source of endogenous SRIF

The effect of SRIF and its antagonist cyclo(7-aminoheptanonyl-Phe-D-Trp-Lys-Thr magnitude of Bzl)(SRIF-A) were studied in sham-operated and bilaterally adrenalectomized rats bearing ACTH- and angiotensin II (ANG-II)-responsive adrenocortical autotransplants. SRIF-A (10(-5) M) completely annulled SRIF (10(-6) M)-induced inhibition of ANG-II (10(-8) M)-evoked rise in aldosterone (ALDO) secretion by both dispersed zona glomerulosa (ZG) cells and autotransplant slices. A 7-day intraperitoneal infusion with SRIF (0.3 nmol.kg-1.min-1) significantly lowered plasma ALDO concentration (PAC) in both groups of animals, without affecting plasma renin activity and the plasma levels of ACTH and corticosterone. This treatment caused a marked atrophy of adrenal ZG and its parenchymal cells (without inducing any significant change in the zona fasciculata morphology), as well as of ZG-like cells of autotransplants. Isolated ZG cells and autotransplant slices from SRIF-infused rats evidenced a notable decrease in both their basal and maximally ACTH- or ANG-II-stimulated ALDO production. The simultaneous infusion of rats with SRIF-A (3 nmol.kg-1.min-1) completely reversed all these effects of SRIF. The prolonged infusion with SRIF-A alone caused, in sham-operated rats, a marked increase in PAC and a significant hypertrophy of ZG and ZG cells; basal and maximally-stimulated ALDO secretion of dispersed ZG cells was also notably raised. Conversely, SRIF-A infusion did not evoke any appreciable effect in autotransplanted rats. These findings suggest that endogenous SRIF is specifically involved in the negative control of the secretion and growth of the rat adrenal ZG. Since regenerated adrenocortical autotransplants, which are responsive to SRIF but not to SRIF-A infusion, are completely deprived of chromaffin cells, the hypothesis is advanced that adrenal zona medullaris may be the source of endogenous SRIF regulating ZG function.

Effects of neuromedin U (NMU)-8 on the rat hypothalamo-pituitary-adrenal axis. Evidence of a direct effect of NMU-8 on the adrenal gland

A 6-day subcutaneous (s.c.) treatment of adult rats with NMU-8 (1.5 or 6 micrograms/100 g/day) increased the average volume of zona fasciculata cells and decreased the number of zona reticularis cells in the adrenal cortex. The lower dose of NMU-8 did not change blood ACTH concentration and adrenal weight, but it notably enhanced serum corticosterone level and basal corticosterone output by adrenal slices. ACTH blood level increased after ether stress in both control and NMU-8-treated rats, but stress-evoked rise in serum corticosterone was observed only in control rats. The higher dose of NMU-8 increased the level of circulating ACTH; however, it decreased adrenal weight and had no effect on serum corticosterone concentration and basal corticosterone output by adrenal slices. NMU-8 (10(-10)/10(-6) M) did not affect basal and ACTH-stimulated corticosterone yield by isolated adrenocortical cells, nor did it change their cytosolic Ca2+ concentration. NMU-8 (10(-8) M) markedly raised basal corticosterone secretion by adrenal slices (including cortex and medulla); higher concentrations of NMU-8 (10(-7)/10(-6) M) were ineffective on basal corticosterone secretion, but strongly inhibited the response to ACTH stimulation. On the ground of these findings it seems reasonable to suggest that NMU-8 exerts a biphasic effect on the function of the peripheral branch of the hypothalamo-pituitary-adrenal axis in rats: NMU-8 at low doses directly stimulates the function and growth of the adrenal cortex, while at high doses exerts a direct inhibitory action.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy but not adrenal demedullation during pregnancy prevents the growth-retarding effects of fetal alcohol exposure

Growth retardation, both in the prenatal and the early neonatal period, is a consistent feature of fetal alcohol exposure, but the mechanism by which alcohol affects growth has not been elucidated. Because other stressors--such as maternal restraint and neonatal glucocorticoid treatment--can also affect growth, we examined the effect of ethanol on pup birthweight under two experimental conditions that altered maternal adrenal function. In the first study when dams were adrenalectomized and given low replacement doses of dexamethasone, the ethanol-exposed offspring of the adrenalectomized dams had birthweights similar to those of dams maintained on regular lab chow diets. In a second study, we found that maternal adrenal demedullation did not alter the reduction in birthweight produced by fetal ethanol exposure. The results suggest that the effects of ethanol on fetal growth may be mediated in part through ethanol-induced changes in the function of the maternal adrenal cortex.

A comparative study of the effect of atrial natriuretic peptide (ANP) on the secretory activity of rat adrenal cortex and angiotensin-II-responsive adrenocortical autotransplants

Rat adrenocortical autotransplants regenerated from capsular-tissue fragments implanted in the musculus gracilis displayed an in-vitro basal gluco- and mineralocorticoid secretion qualitatively similar to that of adrenal quarters from control rats. Moreover, like adrenal quarters, they responded to angiotensin-II (Ang-II, 10(-8) M) by raising their yield of 18-hydroxylated steroids (18-hydroxy-11-deoxycorticosterone, 18-hydroxycorticosterone and aldosterone). ANP (10(-8) M), one of the main negative modulators of the zona-glomerulosa (ZG) mineralocorticoid secretion, totally blocked the ANG-II stimulating effect on adrenal quarters, but not that on adrenocortical autotransplants. Autoradiography showed that, in contrast with ZG cells of control rats, ZG-like cells of transplants did not significantly bind 125I-ANP. The hypothesis is discussed that ZG-like cells of regenerated adrenocortical nodules lack specific receptors for ANP.

Evidence that an extrahypothalamic pituitary corticotropin-releasing hormone (CRH)/adrenocorticotropin (ACTH) system controls adrenal growth and secretion in rats

Within two weeks, hypophysectomy induced in rats a striking decrease in the level of circulating ACTH (the concentration of which was at the limit of sensitivity of our assay system), coupled with a net reduction in the plasma corticosterone concentration and an evident adrenal atrophy. Zona fasciculata, the main producer of glucocorticoids, was decreased in volume, due to a lowering in both the number and average volume of its parenchymal cells. Subcutaneous ACTH infusion (0.1 pmol.min-1), administered during the last week following hypophysectomy, restored the normal blood level of ACTH and completely reversed all effects of hypophysectomy on the adrenals. Subcutaneous infusion for one week with alpha-helical-CRH or corticotropin-inhibiting peptide (1 nmol.min-1), which are competitive inhibitors of CRH and ACTH, evoked a further significant lowering of plasma corticosterone concentration and markedly enhanced adrenal atrophy in hypophysectomized rats. These findings strongly suggest that an extrahypothalamic pituitary CRH/ACTH system may be involved in the maintenance of the growth and steroidogenic secretory activity of the rat adrenal cortex.

Effects of galanin on the secretory activity of the rat adrenal cortex: in vivo and in vitro studies

Galanin, a 28-amino-acid peptide originally isolated from pig intestine, was found to cause dose-dependent rises in the plasma concentration of corticosterone in hypophysectomized rats and in both basal and submaximally ACTH-stimulated in vitro corticosterone production by adrenal quarters and isolated zona fasciculata/reticularis cells. These findings indicate that galanin exerts a direct glucocorticoid secretagogue effect on the inner adrenocortical zones and suggest that galanin, high concentrations of which are contained in adrenal chromaffin cells, may be included in that group of regulatory peptides, by way of which adrenal zona medullaris is thought to exert a paracrine control on the function of the zona corticalis. Galanin was also found to increase the plasma level of aldosterone in hypophysectomized rats in a dose-dependent manner without inducing changes in natremia, kalemia, plasma renin activity, or ACTH plasma concentration. Galanin did enhance both basal aldosterone output and that following submaximal ACTH or angiotensin II stimulation aldosterone output from adrenal quarters, but not from isolated zona glomerulosa cells. This last, rather unexpected, result suggests that galanin exerts an indirect mineralocorticoid secretagogue action, which seems to require the structural integrity of the adrenal cortex and the presence of the adrenal medulla. The hypothesis is advanced that galanin may control the release of some medullary peptides, which in turn may affect mineralocorticoid secretion of the zona glomerulosa in a paracrine manner.

The effects of ageing on the morphology and function of the zonae fasciculata and reticularis of the rat adrenal cortex

The morphological counterpart of the well-known age-dependent marked impairment of glucocorticoid secretion of rat adrenals was investigated by use of morphometric techniques. For this purpose 4-, 8-, 16- and 24-month-old rats were studied. Despite the notable lowering of both basal and ACTH-stimulated production of corticosterone by collagenase-dispersed inner adrenocortical cells, ACTH and corticosterone plasma concentrations displayed significant increases with ageing. Zona fasciculata (ZF) and zona reticularis (ZR) showed a notable hypertrophy in aged rats, which was due to rises in both the average volume and number of their parenchymal cells. The hypertrophy of ZF and ZR cells was in turn associated with increase in the volume of the mitochondrial compartment and proliferation of smooth endoplasmic reticulum, i.e., the two organelles involved in steroid-hormone synthesis. All these morphologic changes, conceivably due to the chronic exposure to high levels of circulating ACTH, are interpreted as a response enabling ZF and ZR to compensate for their age-dependent lowering in glucocorticoid secretion. Stereology also demonstrated that ZF and ZR cells underwent a striking age-related lipid-droplet repletion. Lipid droplets are the intracellular stores of cholesterol esters, the obligate precursors of steroid hormones in rats. This finding is in keeping with the contention that the mechanism underlying the age-dependent decline in rat-adrenal glucocorticoid secretion mainly involves impairments of the utilization of intracellular cholesterol previous to its intramitochondrial transformation to pregnenolone.

Autotransplantation of the adrenal cortex: a morphological and autoradiographic study

A morphological and autoradiographic study was made of the adrenal gland of adult male rats after autotransplantation. The simple technique involved placement of pieces of the adrenal gland in a dorsal plane between the skin and muscle. Animals for morphological studies were sacrificed at 2, 3, 4, 7, 15, 30, 90, and 180 days after autotransplantation. Those for autoradiographic studies were sacrificed at 2, 3, 7, and 15 days after autotransplantation, with 3H-thymidine being administered intraperitoneally 2 h before sacrifice. Sham-operated animals were used as controls. The majority of glandular adrenal cells suffered necrosis in the first days (2 and 3) after autotransplantation. Up until 15 days and after revascularization, morphological features of the cells were compatible with protein synthesis exhibiting a developed RER, scarce SER, and mitochondria with tubular and lamellar cristae. These data may correspond to a proliferative phase of glandular cells. At day 15, cells showed morphological signs of steroidogenic activity (mitochondria with vesicular cristae, increase of SER), and at day 30, an increased number of microvilli were seen. Between 30 and 90 days zonation of the adrenal was evident with glomerulosa, fasciculata, and reticular zones readily apparent. The quantitative analysis showed a significant increase of the volumetric density of mitochondria and microvilli between the days 7 and 30. Autoradiographic studies showed an intense labelling of fibroblast-like cells at days 2 and 3 and of glandular cells at days 7 and 15, which was confirmed by the quantitative studies. Corticosterone in autotransplanted animals decreased during the first 15 days, but after 30 days the values were similar to controls. The model reported here seems to be good for study of the regeneration of the adrenal gland and can be a simple, useful, and reproducible method for adrenal transplantation.

Age-related changes in the morphology and function of the zona glomerulosa of the rat adrenal cortex

The age-related changes in the morphology and function of rat adrenal zona glomerulosa (ZG) were investigated by coupled stereological and radioimmunological techniques. For this purpose 4-, 8-, 16- and 24-month-old rats were studied. Aging caused a notable lowering in the plasma aldosterone concentration and a marked decrease in both basal and ACTH- or angiotensin II (ANG-II)-stimulated secretion of collagenase-dispersed ZG cells. Plasma renin activity (PRA) underwent an age-dependent decrease, while the plasma level of ACTH displayed a significant rise. ZG and its parenchymal cells did not evidence any age-related morphologically demonstrable alteration in their growth, nor ZG cells showed any marked ultrastructural change, with the exception of a severe lipid-droplet repletion. This last finding is in keeping with the aging-induced decrease in the secretory activity of ZG cells, inasmuch as lipid droplets are the intra-cellular stores of cholesterol esters, the obligate precursors of steroid hormones in rat adrenals. ACTH and ANG-II are well known to be involved in the maintenance of the growth of rat ZG; thus, the combined impairment of ANG-II production (as evidenced by PRA lowering) and increase in ACTH secretion may maintain unchanged ZG growth during aging.

Comparison of ACTH and corticotropin-releasing hormone effects on rat adrenal steroidogenesis in vitro

The effects of equimolar concentrations (10(-9) M) of ACTH and corticotropin-releasing hormone (CRH) on the secretory activity of zona glomerulosa (ZG) and zonae fasciculata and reticularis (ZF/ZR) of rat adrenals were investigated in vitro by high-pressure liquid chromatography. ACTH enhanced the output of all the post-progesterone steroids (11-deoxycorticosterone, 18-hydroxy-11-deoxycorticosterone, corticosterone, 18-hydroxycorticosterone, and aldosterone) both by isolated ZG or ZF/ZR cells and by adrenal slices. CRH raised the secretory activity exclusively of adrenal slices, and its effect was less than half that of ACTH. However, the extents to which the various post-progesterone hormones contributed to the ACTH- or CRH-induced rises in the overall adrenal secretory activity were similar. The hypothesis is discussed that CRH acts on the rat adrenal gland by eliciting a local production of ACTH.

Effects of prolonged sodium restriction on the morphology and function of rat adrenocortical autotransplants

Regenerated adrenocortical nodules were obtained by implanting fragments of the capsular tissue of excised adrenal glands into the musculus gracilis of rats (Belloni et al. 1990). Five months after the operation, operated rats showed a normal basal blood level of corticosterone, but a very low concentration of circulating aldosterone associated with a slightly increased plasma renin activity (PRA). Regenerated nodules were well encapsulated and some septa extended into the parenchyma from the connective-tissue capsule. The majority of parenchymal cells were similar to those of the zonae fasciculata and reticularis of the normal adrenal gland, while zona glomerulosa-like cells were exclusively located around septa (juxta-septal zone; JZ). In vitro studies demonstrated that nodules were functioning as far as glucocorticoid production was concerned, while mineralocorticoid yield was very low. Prolonged sodium restriction significantly increased PRA and plasma aldosterone concentration, and provoked a marked hypertrophy of JZ, which was due to increases in both the number and average volume of JZ cells. Accordingly, the in vitro basal production of aldosterone and other 18-hydroxylated steroids was notably enhanced. The plasma level of corticosterone, as well as zona fasciculata/reticularis-like cells and in vitro production of glucocorticoids by regenerated nodules were not affected. These findings, indicating that autotransplanted adrenocortical nodules respond to a prolonged sodium restriction similar to the normal adrenal glands, suggest that the relative deficit in mineralocorticoid production is not due to an intrinsic defect of the zona glomerulosa-like JZ, but is probably caused by the impairment of its adequate stimulation under basal conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute action of polypeptide YY (PYY) on rat adrenocortical cells: in vivo versus in vitro effects

Polypeptide YY (PYY), a 36-amino-acid peptide contained in high concentration in the chromaffin granules of adrenal medullary cells, significantly raised aldosterone (but not corticosterone) plasma level, when acutely administered intraperitoneum to rats at a dose of 25 microM.kg-1. Conversely, the exposure to PYY (10(-6) M) notably and specifically depressed both basal and ACTH-stimulated production of 18-hydroxylated steroids (aldosterone, 18-hydroxy-corticosterone and 180H-DOC) by isolated rat zona glomerulosa cells. The discrepancy between in vivo and in vitro results is tentatively explained by assuming that the direct inhibitory effect of PYY on aldosterone secretion by rat zona glomerulosa is masked in vivo by the interference of this peptide with one or more of the various factors that are involved in the multifactorial regulation of zona glomerulosa function.