Immunohistochemical localization of adrenal ferredoxin and distribution of adrenal ferredoxin and cytochrome P-450 in the rat adrenal

Adrenal ferredoxin, the iron-sulfur protein associated with cytochromes P-450 in adrenocortical mitochondria, has been localized immunohistochemically at the light microscopic level in rat adrenals by employing rabbit antiserum to bovine adrenal ferredoxin in both an unlabeled antibody peroxidase-antiperoxidase method and an indirect fluorescent antibody method. When sections of rat adrenals were exposed to the adrenal ferredoxin antiserum in both procedures, positive staining for adrenal ferredoxin was observed in parenchymal cells of the three cortical zones but not in medullary chromaffin cells. Marked differences in the intensity of staining, however, where observed among the three cortical zones: the most intense staining being found in the zona fasciculata, less in the zona reticularis, and least in the zona glomerulosa. Furthermore, differences in staining intensity were also observed among cells within both the zona fasciculata and the zona reticularis. In agreement with these immunohistochemical observations, determinations of adrenal ferredoxin contents by electron paramagnetic resonance (EPR) spectrometry in homogenates prepared from capsular and decapsulated rat adrenals revealed that the concentration of adrenal ferredoxin in the zona glomerulosa was lower than that in the zona fasciculata-reticularis. Similar results were obtained when the contents of cytochrome P-450 were determined in capsular adn decapsulated rat adrenal homogenates. These observations indicate that adrenal ferrodoxin and cytochrome P-450 are not distributed uniformly throughout the rat adrenal cortex.     

Ultrastructure of the normal human adrenal cortex]

Electron-microscopic investigations on the human adrenal cortex have been carried out in order to elucidate ultrastructural differences in the various zones. These studies indicate that certain differences in the ultrastructure of the mitochondria may be particularly useful as criteria to differentiate the three cortical zones. In this regard, the appearance of two types of mitochondria in the zona glomerulosa as well as in the zona fasciculata is of obvious interest. The probability of a relationship between the activity of the different cortical zones and the predominant presence of one form of mitochondria has been suggested. In addition, ultrastructural transformations following stress situations as well as problems dealing with the so-called 'dark and light cells' and the basal membrane are discussed.     

Relationship between mitochondrial lipid peroxidation and alpha-tocopherol levels in the guinea-pig adrenal cortex

Lipid peroxidation in mitochondria from the functionally distinct inner (zona reticularis) and outer (zona fasciculata + zona glomerulosa) zones of the guinea-pig adrenal cortex was investigated. Ferrous ion (Fe2+)-induced lipid peroxidation was far greater in inner than outer zone mitochondria. Ascorbic acid similarly initiated lipid peroxidation to a greater extent in inner zone mitochondrial preparations. Differences in the unsaturated fatty acid content of inner and outer zone mitochondria could not account for the regional differences in lipid peroxidation. Total fatty acid concentrations were greater in the outer than in the inner zone, and the relative amounts of each fatty acid were similar in the two zones. However, mitochondrial concentrations of alpha-tocopherol, an antioxidant known to inhibit lipid peroxidation, were approx. 5-times greater in the outer than inner zone. The results demonstrate that there are regional differences in mitochondrial lipid peroxidation in the adrenal cortex which may be attributable to differences in alpha-tocopherol content. Thus, alpha-tocopherol may serve to protect outer zone mitochondrial enzymes from the consequences of lipid peroxidation and thereby contribute to some of the functional differences between the zones of the adrenal cortex.     

Regional distribution of microsomal drug and steroid metabolism in the guinea pig adrenal cortex

The regional distribution of steroid and drug metabolism was studied in intact cells and microsomal fractions obtained from the chromatically distinct inner (zona reticularis) and outer (zona fasciculata plus zona glomerulosa) zones of the guinea pig adrenal cortex. Cells isolated from the outer cortical zone produced far more cortisol than cells from the inner zone and cortisol production was stimulated by adrenocorticotropic hormone only in cells from the outer zone. Among the factors which may contribute to the greater cortisol production by the outer zone are a higher rate of 17 alpha-hydroxylation and ratio of 17 alpha- to 21-hydroxylase activities in that zone, both of which favor cortisol synthesis. In contrast, steroid 21-hydroxylase activity was far greater than 17 alpha-hydroxylase activity in microsomes obtained from the inner zone of the adrenal cortex. Microsomal metabolism of various xenobiotics such as benzo(a)pyrene and ethylmorphine proceeded far more rapidly in the inner than outer cortical zone. The zonal differences in metabolism appeared to result in part from differences in the ability of xenobiotics to interact with microsomal cytochromes P-450 in the two zones. The results indicate that the inner zone has a minor role in cortisol production by the adrenal cortex, but its involvement in the production of other steroids cannot be excluded. In contrast, the inner zone appears to have the major role in the metabolism of at least some xenobiotics which may account for its greater vulnerability to the toxic effects of chemicals requiring metabolic activation.     

An ultrastructural study of the adrenal cortex in Cushing's syndrome without and with hyperaldosteronism]

This paper reports ultrastructural comparision of the adrenal gland zones of a rare case of a combination from Cushing's syndrome and hyperaldosteronism with a pure Cushing's syndrom and with a normal human adrenal gland. Whilst between the zona glomerulosa of the normal adrenal gland and of the Cushing's syndrom there are no differences, the morphological state of the glomerulosa cells of the Cushing's syndrom in combination with hyperaldosteronism is interpreted as an inhibition of the activity of these cells. In the cells of the hyperplastic zona fasciculata of Cushing's syndrom in combination with hyperaldosteronism, there are no electronmicroscopical characteristics, who are morphological equivalent of the production of aldosterone. The abundant quantity of steroid producing organells in these cells point to a high function. The cells of the adenoma of Cushing's syndrom contain abundant vacuols of lipids, in which presumable are stored steroid hormones.     

Differential effects of adrenocorticotropic hormone on steroid hydroxylase activities in the inner and outer zones of the guinea pig adrenal cortex.

We have studied the effects of ACTH treatment on steroid hydroxylase activities in the inner (zona reticularis) and outer (zona fasciculata plus zona glomerulosa) zones of the guinea pig adrenal cortex. Animals received 5 or 10 U of ACTH daily for 6 days and enzyme activities were then assessed in isolated microsomal or mitochondrial preparations. In control animals, microsomal cytochrome P-450 concentrations were greater in the inner than outer zone, but mitochondrial P-450 levels were similar in the two zones. Microsomal 17 alpha-hydroxylase and mitochondrial 11 beta-hydroxylase activities were greater in the outer than inner zone, but microsomal 21-hydroxylase activity was greater in the inner zone. ACTH treatment decreased cytochrome P-450 concentrations in inner but not outer zone microsomes; mitochondrial P-450 levels were unaffected in both zones. ACTH caused a dose-dependent increase in inner zone 17 alpha-hydroxylase activity and decrease in 21-hydroxylase activity without affecting the activity of either enzyme in outer zone microsomes. ACTH also decreased 11 beta-hydroxylase activity in outer but not inner zone mitochondrial preparations. The net effect of ACTH treatment was to diminish the differences in steroid metabolism between the two zones. The results indicate that the effects of ACTH on steroid hydroxylase activities are both zone- and enzyme-dependent, suggesting the existence of multiple and independent regulatory mechanisms.     

Aldosterone biosynthesis in mitochondria of isolated zones of adrenal cortex

An assumption that the aldosterone-synthesizing enzyme exists only in zona glomerulosa cells apparently contradicts our recent findings that a purified bovine adrenocortical cytochrome P-45011 beta catalyzes the aldosterone formation and the enzyme exists in both zones of the adrenal cortex. To gain more insight into the zone specificity of aldosterone production, the aldosterone-synthesizing activity of mitochondria prepared from the isolated zones of adrenal cortex of various animal species was investigated. The intact mitochondria from the bovine or porcine zonae fasciculata-reticularis could not produce aldosterone whereas those from the zona glomerulosa produced it at a significant rate. When the mitochondria from the zonae fasciculata-reticularis were solubilized by the addition of cholate, they produced aldosterone from corticosterone at a rate comparable to that of those from the zona glomerulosa. The presence of specific factor(s) in the zonae fasciculata-reticularis mitochondria inhibiting expression of the aldosterone synthetic activity is discussed. The mitochondria of the rat zonae fasciculata-reticularis could hardly catalyze aldosterone synthesis under the detergent-solubilized conditions, whereas those of the zona glomerulosa could. Immunoblot analysis revealed that the mitochondria of the zonae fasciculata-reticularis contained a protein of Mr 51,000 which was immunocrossreactive with a monoclonal antibody directed against P-45011 beta, whereas those of the zona glomerulosa contained two immunocrossreactive proteins of Mr 51,000 and 49,000. These results suggest that in the case of rat adrenal cortex, a specific aldosterone-synthesizing enzyme exists in the zona glomerulosa.     

Sex differences in adrenocortical structure and function

Summary Adrenal glands of adult female rats are heavier than the glands of corresponding male rats. Postpubertal orchiectomy increases the adrenal weight, an effect restored by testosterone replacement. Under the same conditions ovariectomy of 8 weeks duration does not change the adrenal weight while estradiol replacement enhances the relative adrenal weight.Karyometric studies have shown that nuclei in the female zona fasciculata cells are larger (app. 18%) than those of the male. Similar but only slight differences (2%) were observed in the zona reticularis. Orchiectomy results in enlargement of cell nuclei within all zones of the adrenal cortex; testosterone replacement has the opposite effect. Ovariectomy of 8 weeks duration slightly enhances the volume of nuclei of the zona glomerulosa cells, has no effect on the nuclei of the zona fasciculata and reduces the volume of nuclei in the zona reticularis. Estradiol replacement reduces the volume of nuclei of the zona glomerulosa cells but increases nuclear volume in the zona fasciculata and in the zona reticularis.Thus testosterone has an inhibitory effect on the adrenal cortex of the rat while the physiologic effect of estradiol on the morphology of this gland, particularly on the zona fasciculata cells is rather dubious.The author wishes to thank Mrs. B. Westerska and Miss K. Siejak for excellent technical assistance.This research was supported in part by a grant from the Zoological Committee, 2nd Department, Polish Academy of Sciences.This paper is dedicated to the memory of late Kazimierz Mietkiewski, M.D., Ph.D. whose encouragements and suggestions were most stimulating for my work.     

Low-density lipoprotein receptor activity in the guinea pig adrenal cortex. II. Zonal response to aminoglutethimide and 17 alpha-ethinylestradiol

Low-density lipoprotein (LDL) receptor activity and the concentration of cholesterol were measured in the outer (glomerulosa/fasciculata) and inner (reticularis) zones of the adrenal cortex of the guinea pig to examine the relation between cholesterol content and LDL receptor activity. While the concentration of cholesterol was 2-3-times higher in the outer cortical zone, the maximum high-affinity binding capacity for LDL was essentially the same for the two zones, or slightly higher for the inner zone. Adrenocorticotrophic hormone (ACTH) caused a significant increase in LDL receptor activity only in the outer zone, but led to a reduction in the cholesterol content in both adrenocortical zones. The treatment of animals with 17 alpha-ethinyl-estradiol also resulted in a reduction of cholesterol in both adrenocortical zones, but an increase in LDL receptor number only in the outer zone. The latter effect was partially reversed by the administration of dexamethasone. Aminoglutethimide, which was used in a dose that did not block steroidogenesis but did block the hydrolysis of cholesteryl esters in response to ACTH, did not prevent the ACTH-induced increase in LDL receptor number in the outer zone. Thus, the number of LDL receptors was increased in the zona fasciculata by ACTH in the absence of a reduction in cellular cholesterol content, while the number of LDL receptors in the zona reticularis was not increased by ACTH even in the face of a reduction in cellular cholesterol. Exclusive of the experiments employing aminoglutethimide, when the cellular cholesterol content was plotted against LDL binding activity, an excellent inverse correlation was revealed for the zona fasciculata, but essentially no correlation was noted for the zona reticularis. It is concluded that the outer and inner cortical zones of the guinea pig adrenal are quite distinct in the nature of their LDL receptor activity and regulation: the LDL receptor of the outer zone appears to function in a way similar to what has been reported for the whole adrenal cortex of other species in that receptor number correlates with tissue cholesterol content and is primarily regulated by ACTH; the LDL receptor number of the inner zone, however, does not correlate with tissue cholesterol content and is apparently not regulated by ACTH.     

Immunohistochemical localization of adrenal ferredoxin in bovine adrenal cortex.

Adrenal ferredoxin, the iron-sulfur protein associated with cytochrome P-450 in adrenocortical mitochondria, has been localized at the light microscopic level in bovine adrenal cortex. Localization was achieved through the use of rabbit antiserum to bovine adrenal ferrodoxin in an unlabeled antibody peroxidase-antiperoxidase method. When sections of bovine adrenal glands were exposed to the adrenal ferredoxin antiserum, intense staining was observed in parenchymal cells of the three cortical zones. Staining for adrenal ferredoxin was not detected in the medullary chromaffin cells. The presence of adrenal ferredoxin in the three cortical zones was verified by electron paramagnetic resonance spectrometry. These determinations also revealed that while the zona fasciculata and the zona reticularis contained approximately equal concentrations of adrenal ferredoxin, the concentration of the iron-sulfur protein in the zona glomerulosa was considerably lower. Similar results were obtained when the levels of cytochrome P-450 were determined in the three cortical zones. These results represent the first immunohistochemical localization within an intact tissue or cell of any component of an NADPH-dependent electron transport sequence which is responsible for the reduction of cytochrome P-450.     

Steroidogenic characteristics of the adrenal cortex of the mare studied by electron microscopy

The three concentric zones of the horse adrenal cortex (zonae glomerulosa, fasciculata and reticularis) showed marked interpenetration and exhibited a different relative development according to their position in the gland. Whereas the three cortical zones each had a specific histological structure, the ultrastructure of their cells showed a certain qualitative homogeneity. The differences corresponded essentially to the relative abundance of the constituents which are generally considered typical of steroidogeneous cells: mitochondria with vesicular cristae, smooth endoplasmic reticulum and lipid droplets. Their importance increased progressively from the zona glomerulosa to the zona reticularis. In this zone, the presence of gap and septate-like cell junctions, and mitochondria with vesicular cristae in close proximity to a smooth endoplasmic reticulum with numerous dilated tubules, suggested that steroidogenesis may be the most active. Ultrastructural findings were indicative of only quantitative differences between the steroidogenic capacities of the three zones of the mare adrenal cortex.     

Trophic and steroidogenic effects of water deprivation on the adrenal gland of the adult female rat

The effects of a 3-day water deprivation were studied in adult female rats in order to know what are the different zones of the adrenal gland and the hormonal factors involved in the growth and the activity of the adrenal gland. Water deprivation significantly increased plasma renin activity (PRA), plasma Angiotensin II (AII), vasopressin (AVP), epinephrine, aldosterone and corticosterone concentrations but did not modify the plasma adrenocorticotropin hormone (ACTH) level. Water deprivation significantly increased the absolute weight of the adrenal capsule containing the zona glomerulosa without modification of the density of cells per area unit suggesting that the growth of the adrenal capsule was due to a cell hyperplasia of the zona glomerulosa. Water deprivation significantly increased the density of AII type 1 (AT₁) receptors in the adrenal capsule but did not modify the density of AII type 2 (AT₂) receptors in the adrenal capsule and core containing the zona fasciculata, the zona reticularis and the medulla. The treatment of dehydrated female rats with captopril, which inhibits the angiotensin converting enzyme (ACE) in order to block the production of AII, significantly decreased the absolute weight of the adrenal capsule, plasma aldosterone and the density of AT₁ receptors in the adrenal capsule. The concentration of corticosterone in the plasma, the density of AT₂ receptors and the density of cells per unit area in the zona glomerulosa of the adrenal capsule were not affected by captopril-treatment. In conclusion, these results suggest that AII seems to be the main factor involved in the stimulation of the growth and the secretion of aldosterone by the adrenal capsule containing the zona glomerulosa during water deprivation. The low level of plasma ACTH is not involved in the growth of the adrenal gland but is probably responsible for the secretion of corticosterone by the zona fasciculata.     

Regional differences in microsomal lipid peroxidation and antioxidant levels in the guinea pig adrenal cortex

Lipid peroxidation (LP) and antioxidant levels were studied in the chromatically distinct inner (zona reticularis) and outer (zona fasciculata + zona glomerulosa) zones of the guinea pig adrenal cortex. Ferrous ion (Fe2+) produced a concentration-dependent (10(-5) to 10(-3) M) stimulation of microsomal LP in both zones, but LP, as estimated by malonaldehyde production, was far greater in the inner zone. Although cytosolic ascorbic acid content was similar in the two zones, microsomal tocopherol levels were approx 4 times greater in the outer than inner zone. Subphysiological concentrations of ascorbic acid, like Fe2+, initiated LP to a greater extent in inner than outer zone microsomes; optimal stimulation of LP by ascorbic acid occurred at concentrations of 100-200 microM in both zones. Physiological concentrations of ascorbic acid (1-5 mM), by contrast, did not initiate LP and, in fact, markedly inhibited Fe2+-induced LP in both inner and outer zone microsomal preparations. Outer zone microsomes were more sensitive to the antioxidant effects of ascorbic acid than were inner zone preparations. Addition of alpha-tocopherol to inner zone microsomal suspensions inhibited Fe2+-induced LP. The results indicate that there are regional differences in adrenocortical LP which may be caused by differences in tocopherol content. alpha-Tocopherol may serve important antioxidant functions within the adrenal cortex, thereby contributing to the functional zonation of the gland.     

Morphology and ultrastructure of the adrenal gland in Bactrian camels (Camelus bactrianus)

In the present study, we examined the morphological features of the adrenal gland in Bactrian camel by means of digital anatomy, light and electron microscopy. Our findings testified that the gland was divided into three parts, capsule, cortex and medulla from outside to inside as other mammals, and the cortex itself was further distinguished into four zones: zona glomerulosa, zona intermedia, zona fasciculate and zona reticularis. Notably, the zona intermedia could be seen clearly in the glands from females and castrated males, whereas it was not morphologically clear in male. There was a great deal of lipid droplets in the zona fasciculate, while it was fewer in the zona glomerulosa and zona reticularis. The cytoplasm of adrenocortical cell contained rich mitochondria and endoplasmic reticulum. The adrenal medulla was well-developed with two separations of external and internal zones. The most obvious histological property of adrenal medulla cells were that they contained a huge number of electron-dense granules enveloped by the membrane, and so medulla cells could be divided into norepinephrine cells and epinephrine cells. Moreover, the cortical cuffs were frequently present in adrenal gland. Results of this study provides a theoretical basis necessary for ongoing investigations on Bactrian camels and their good adaptability in arid and semi-arid circumstances.     

Strain differences in rabbit adrenocortical structure and morphological evidence of corticomedullary communication

Interstrain differences in the structure of the mouse and rat adrenal cortex are well known, but related data on rabbits are not available. This study was planned to demonstrate possible strain differences in rabbit adrenal morphology and morphological evidence of a communication between cortex and medulla. For this purpose, the zonation of the adrenal cortex of intact mature male and female rabbits of different strains (New Zealand, Chinchilla and California) were compared using morphometry and the corticomedullary junction was evaluated for close relationship. Marked intersex and interstrain differences were found in the adrenocortical zonation. Female rabbits had larger adrenocortical zones than corresponding males. The rabbits of Chinchilla and California strains had the largest cortical sizes. This difference depended largely upon the higher thickness of the zona fasciculata. Whereas, there were no significant strain differences in the thickness of zona glomerulosa and zona reticularis. Furthermore, examination of corticomedullary junction showed that cortex and medulla were interwoven. Single and small accumulations of cortical cells were spread throughout the medulla. Our morphological data showed the presence of significant interstrain differences in the adrenocortical zonation in the rabbits and provide evidence for a possible paracrine interaction between medullary and cortical cells.     

The undifferentiated cell zone is a stem cell zone in adult rat adrenal cortex

The adrenal cortex of mammals has been known to consist of three morphologically and functionally distinct zones, i.e. the zona glomerulosa (zG), the zona fasciculata (zF) and the zona reticularis (zR), each of which secretes a specific corticosteroid different from those produced by the other two zones. We found previously, however, that an additional zone existed between zG and zF of adult rat adrenal cortex and that the cells in that zone were in a functionally undifferentiated state as an adrenocortical cell [Endocrinology 135, (1994) 431]: they were incapable of synthesizing highly active forms of corticosteroids, such as aldosterone and corticosterone, although they could produce their precursors. Hence, we named the zone as the undifferentiated cell zone (zU) of the adrenal cortex. Here we show that zU and its surroundings, i.e. the innermost portion of zG and the outermost portion of zF are the sites for cell replication in adult rat adrenal cortex and that the cells raised there migrate to other regions. Such cell replications in this region occur regardless of physiological conditions, such as the rise and fall of hormonal stimuli and circadian fluctuation of adrenocortical activities. On the bases of these and other findings previously described, we propose that zU is the stem cell zone of the adult rat adrenal cortex. Our recent success in isolating novel cell lines, which display an undifferentiated phenotype similar to that of zU cells, could facilitate the exploration of molecular mechanisms for the differentiation and development of the adrenocortical cells.     

Strain Differences in Adrenal Microsomal Steroid Metabolism in Guinea Pigs

We recently reported that CYP2D16, a xenobiotic-metabolizing P450 isozyme, was expressed at higher levels in adrenal microsomes from inbred Strain 13 guinea pigs than in those from outbred English Short Hair (ESH) animals. Studies were done to determine if there also were strain differences in adrenal microsomal steroid metabolism. In both inner (zona reticularis) and outer (zona fasciculata plus zona glomerulosa) zone preparations of the adrenal cortex, 21-hydroxylase activities were greater in microsomes from ESH than from Strain 13 guinea pigs. By contrast, 17-hydroxylase activities were similar in the two strains. In both strains, 21-hydroxylase activities were greater in inner than outer zone microsomes, but the opposite was found for 17-hydroxylase activities (outer>inner). Northern and Western analyses revealed higher levels of CYP21 mRNA and protein in adrenals from ESH than Strain 13 guinea pigs, but there were no strain differences in CYP17 mRNA or protein concentrations. Despite the zonal differences in adrenal 17-hydroxylase and 21-hydroxylase activities, CYP17 and CYP21 mRNA and protein levels were similar in the inner and outer zones within each strain of guinea pig. The results demonstrate strain differences in microsomal steroid metabolism that are explained by differences in CYP21 expression. By contrast, the zonal differences in steroid hydroxylase activities may be attributable to post-translational mechanisms.     

Investigations on the turnover of adrenocortical mitochondria

Summary The effects of chronic administration of ACTH (up to 36 consecutive days) on the mitochondria of the zona reticularis of the rat adrenal cortex were investigated by stereologic techniques. It was found that ACTH induces two phases of hypertrophy of mitochondria alternating with two proliferative stages, which are associated with a significant decrease in the average volume of the organelles. It is suggested that, as in the zona fasciculata, ACTH controls the processes of growth and division of mitochondria in the zona reticularis. The mechanism underlying this action of ACTH as well as the differences between the responses to ACTH of the mitochondrial population of the two adrenal zones are discussed in the light of evidence indicating that mitochondria contain a complete genetic apparatus largely independent of nuclear control.The authors wish to thank Miss A. Coi and Mr. G. Gottardo for their excellent technical assistance. This work was partly supported by a contract with the CNR (C.T. 73.00663.04)     

Calf adrenocortical fasciculata cells secrete aldosterone when placed in primary culture

Aldosterone production occurs in the outer area of the adrenal cortex, the zona glomerulosa. The glucocortocoids cortisol and corticosterone, depending upon the species, are synthesized in the inner cortex, the zona fasciculata. Calf zona glomerulosa cells rapidly lose the ability to synthesize aldosterone when placed in primary culture unless they are incubated in the presence of the antioxidants butylated hydroxyanisol and selenous acid, the radioprotectant DMSO, and the cytochrome P-450 inhibitor metyrapone. In the presence of these additives, calf zona fasciculata cells in primary culture synthesize aldosterone at rates which can approach those from cells isolated from the zona glomerulosa. Calf zona glomerulosa and fasciculata cells both responded well to ACTH and angiotensin II, but the zona fasciculata cells respond very poorly compared to glomerulosa cells to increased potassium in the media. Rat zona fasciculata cells in primary culture under similar conditions did not synthesize aldesterone, suggesting that the regulation of the expression of the enzymes responsible for the biosynthesis of aldosterone in the two species is different. Two distinct cytochrome P-450 cDNAs which hydroxylate deoxycorticosterone at the 11β position have been described in the rat, human and mouse. Both cytochrome P-450 cDNAs have been cloned and expressed in non-steroidogenic cells, but only one is expressed in the zona glomerulosa and only this glomerulosa cytochrome P450 can further hydroxylate deoxycorticosterone to generate aldosterone. Two bovine adrenal cDNAs have been described with 11β-hydroxylase activity and their expression products in transiently transfected COS cells can convert deoxycorticosterone into aldosterone. Both enzymes are expressed in all zones of the adrenal cortex. Zonal regulation of aldosterone synthesis in the bovine adrenal gland may be due to an 11β-hydroxylase with aldosterone synthesizing capacity which has not yet been isolated. Alternatively, a single enzyme might be responsible for the several hydroxylations in the pathway between deoxycorticosterone and aldosterone and zonal synthesis might be controlled by unknown factors regulating the expression of C-18 hydroxylation. The incubation of zona fasciculata with antioxidants and metyrapone results in atypical expression of this activity by an unclear mechanism.     

Immunohistochemical localization of the somatostatin receptor subtype 2A in the rat adrenal gland

The immunohistochemical localization of the somatostatin receptor subtype sst2A was investigated in the rat adrenal gland using SS-800 polyclonal antibody. The sst2A immunopositivity was found in all adrenocortical zones and in adrenal medulla, the reaction being slightly more intense in zona glomerulosa and medulla. The administration of the potent agonist of sst2 receptors - octreotide - resulted in the enhancement of the immunopositivity in zona glomerulosa and medulla, whereas chronic exposure of the rats to diethylstilbestrol led to enhancement of the immunopositivity in zona glomerulosa and in the external part of zona fasciculata.