Immunohistochemical localization of huntingtin-associated protein 1 in endocrine system of the rat.

Huntingtin-associated protein 1 (HAP1) was originally found to be localized in neurons and is thought to play an important role in neuronal vesicular trafficking and/or organelle transport. Based on functional similarity between neuron and endocrine cell in vesicular trafficking, we examined the expression and localization of HAP1 in the rat endocrine system using immunohistochemistry. HAP1-immunoreactive cells are widely distributed in the anterior lobe of the pituitary, scattered in the wall of the thyroid follicles, or clustered in the interfollicular space of the thyroid gland, exclusively but diffusely distributed in the medullae of adrenal glands, and selectively located in the pancreas islets. HAP1-containing cells were also found in the mucosa of stomach and small intestine with a distributive pattern similar to that of gastrointestinal endocrine cells. However, no HAP1-immunoreactive cell was found in the cortex of the adrenal gland, the testis, and the ovary. In the posterior lobe of the pituitary, HAP1-immunoreactive products were not detected in the cell bodies but in many stigmoid bodies, one kind of non-membrane-bound cytoplasmic organelle with a central or eccentric electron-lucent core. HAP1-immunoreactive stigmoid bodies were also found in the cytoplasm of endocrine cells in the thyroid gland, the medullae of adrenal gland, the pancreas islets, the stomach, and small intestine. The present study demonstrates that HAP1 is selectively expressed in part of the small peptide-, protein-, and amino-acid analog and derivative-secreting endocrine cells but not in steroid hormone-secreting cells, suggesting that HAP1 is also involved in intracellular trafficking in certain types of endocrine cells.     

Differential expression of a stress-modulating gene, BRE, in the adrenal gland, in adrenal neoplasia, and in abnormal adrenal tissues.

Genes that modulate the action of hormones and cytokines play a critical role in stress response, survival, and in growth and differentiation of cells. Many of these biological response modifiers are responsible for various pathological conditions, including inflammation, infection, cachexia, aging, genetic disorders, and cancer. We have previously identified a new gene, BRE, that is responsive to DNA damage and retinoic acid. Using multiple-tissue dot-blotting and Northern blotting, BRE was recently found to be strongly expressed in adrenal cortex and medulla, in testis, and in pancreas, whereas low expression was found in the thyroid, thymus, small intestine and stomach. In situ hybridization and immunohistochemical staining indicated that BRE was strongly expressed in the zona glomerulosa of the adrenal cortex, which synthesizes and secretes the mineralocorticoid hormones. It is also highly expressed in the glial and neuronal cells of the brain and in the round spermatids, Sertoli cells, and Leydig cells of the testis, all of which are associated with steroid hormones and/or TNF synthesis. However, BRE expression was downregulated in human adrenal adenoma and pheochromocytoma, whereas its expression was enhanced in abnormal adrenal tissues of rats chronically treated with nitrate or nitrite. These data, taken together, indicate that the expression of BRE is apparently associated with steroids and/or TNF production and the regulation of endocrine functions. BRE may play an important role in the endocrine and immune system, such as the cytokine-endocrine interaction of the adrenal gland.     

Widespread expression of zinc transporter ZnT (SLC30) family members in mouse endocrine cells

Zinc is abundant in most endocrine cell types, and plays a pivotal role in the synthesis and secretion of many hormones. Recent studies have demonstrated the expression of numerous zinc transporter (ZnT) family members in the pancreas, thyroid, and adrenal glands, suggesting a role for ZnTs in regulating cellular zinc homeostasis in endocrine cells. However, the cellular distribution of ZnTs in the endocrine organs has not been well established. In the present study, the mRNA expression level, cellular distribution of ZnTs as well as liable zinc ions were examined in the mouse pituitary, adrenal glands, thyroid, and pancreas. In general, ZnT1-10 mRNA was expressed to various degrees in the detected endocrine organs, with no detectable ZnT10 mRNA in the pancreas. In the anterior pituitary, both the acidophilic and basophilic cells were immunopositive to ZnT1-5, 7, 8, except for ZnT10. In the adrenal cortex, the immunoreactivity of all the tested ZnTs, including ZnT1-5, 7, 8, 10, was observed in the zona fasciculata, and some ZnTs were detected in the zona glomerulosa, zona reticularis, and the adrenal medulla. Both the follicle epithelial cells and parafollicular cells in the thyroid gland were immunostained with ZnT1-5, 7, 8, but not ZnT10. In the endocrine pancreas, the immunoreactivity of tested ZnTs was observed to various degrees except for ZnT10 in the cytoplasm of islet cells. Furthermore, autometallographic staining showed that liable zinc was observed in the endocrine cells, such as the adrenal cortical cells, thyroid follicle epithelial cells, and the pancreatic islet cells. All together, the wide distribution of liable zinc and the phenomenon that numerous ZnT family members are partially overlapped in a subset of endocrine cells suggest an important role for the ZnT family in controlling cellular zinc levels and subsequently regulating the synthesis and secretion of hormones in the endocrine system.     

Localization of androgen and estrogen receptors in rat and primate tissues

There is now evidence that estrogens and androgens are exerting their effects in different tissues throughout the body. In order to determine the sites of action of these steroids, studies have been performed to identify at the cellular level the localization of androgen receptor (AR) and the two estrogen receptor (ER) subtypes, ERalpha and ERbeta, specially in the rat, monkey and human. In the prostate, AR was observed in the secretory and stromal cells. In the testis, Sertoli, Leydig and myoid cells were labelled. In the epididymis and seminal vesicles, both epithelial and stromal cells contained AR. In the ovary, AR was detected in granulosa and interstitial cells. In the uterus, epithelial, stromal and muscle cells were all immunopositive for AR. In the central nervous system, AR-containing neurons were found to be widely distributed throughout the brain. In the mammary gland, epithelial cells in acini and ducts and stromal cells were demonstrated to express AR. In the skin, AR was detected in keratinocytes, sebaceous and sweat glands, and hair follicles. In addition, AR was also found in anterior pituitary, thyroid, adrenal cortex, liver, kidney tubules, urinary bladder, cardiac and striated muscle, and bone. The ER subtypes are in general differentially expressed. While ERalpha has been predominantly found in anterior pituitary, uterus, vagina, testis, liver and kidney, ERbeta is predominant in thyroid, ovary, prostate, skin, bladder, lungs, gastro-intestinal tract, cartilage and bone. In tissues which contain both receptor subtypes, such as ovary, testis and various regions of the brain, a cell-specific localization for each ER subtype has been generally observed. Altogether, the recent results on the cellular localization of sex steroid receptors will certainly contribute to a better understanding of the specific role of these steroids in different target organs.     

Testicular and adrenocortical function in healthy men and in men with benign prostatic hyperplasia.

The influence of aging upon serum concentrations of testicular steroids, sex hormone binding globulin (SHBG) and pituitary hormones and on adrenal steroid levels and adrenal steroid response to ACTH was studied in 81 healthy men aged 20-87 years. These endocrine variables were also compared in 43 patients with benign prostatic hyperplasia (BPH), aged 58-89 years and in a subgroup of 41 men, aged 58-87 years, from the above mentioned reference population. The normal endocrine aging was characterized by a rise in SHBG levels, decreasing levels of testicular steroids and non-SHBG-bound testosterone (NST) and increasing gonadotropin levels and decreasing concentrations of total estrone. Adrenal androgen levels decreased in the presence of unchanged levels of cortisol and the adrenal steroid response to ACTH changed by decreasing increments in dehydroepiandrosterone (DHA) and increasing increments in 17 alpha-hydroxyprogesterone (17OHP). With the exception of the alterations in SHBG and adrenal androgens, all these changes were finished before the seventh decade of life. BPH patients had elevated levels of testosterone and NST in the presence of normal SHBG and gonadotropin levels, elevated levels of DHA and DHA sulfate (DHAS) in the presence of normal cortisol levels, a "younger" pattern of adrenal steroid response to ACTH as judged from the increments in DHA and 17OHP, elevated ratios between estrone and 4-androstene-3,17-dione suggesting an increased peripheral aromatization and subnormal prolactin levels. BPH patients may be considered as "endocrinologically younger" than healthy subjects. DHA and especially its proximate metabolite 5-androstene-3 beta, 17 beta-diol exert powerful estrogenic effects on the receptor level. Thus the elevated levels of DHA and DHAS in the BPH patients may create an hyperestrogenic condition in addition to the slight hyperandrogenicity caused by the elevated NST levels. Both endocrine aberrations may play a role in the etiology of BPH, in accordance with the dual sex steroid sensitivity of the periurethral glands.     

Steroidogenesis activator polypeptide (SAP) in the rat ovary and testis

A steroidogenesis activator polypeptide (SAP) has previously been identified in the rat adrenal cortex (Pedersen and Brownie, Proc. natn. Acad. Sci. U.S.A. 80 (1983) 1882-1886). This factor apparently facilitates the association of mitochondrial cholesterol with the cholesterol side-chain cleavage cytochrome P-450, a reaction which is generally regarded as rate-controlling in the steroid biosynthetic pathway. The same preparative techniques have now been applied in a search for this material in other rat tissues. Among those investigated, the ovary and testis demonstrate significant concentrations of a factor which is biologically and chromatographically similar to adrenal SAP. In the immature ovary the activator becomes manifest after priming with PMSG and rises dramatically during hCG-stimulated luteinization, an increase which can be blunted with cycloheximide. In the adult rat testis it is increased acutely by treatment with hCG or dibutyryl cAMP and is diminished in response to hypophysectomy or cycloheximide. At approximately equivalent concentrations (10(-7) M), preparations of the activator from the adrenal cortex, the testis, and the superovulated ovary each enhance the activity of cholesterol side-chain cleavage in adrenocortical mitochondria by 5- to 6-fold over basal controls. We conclude that steroidogenic organs share a similar or identical intracellular modulator of cholesterol----pregnenolone conversion which is under pituitary control.     

Peripheral and CNS Effects of the Pineal Gland: Target Enzymes Common to Tissues and Species

The pineal gland is an important transducer mediating environmentalinfluences on endocrine organs. It has direct effects on thehypothalamus and pancreas and indirect effects on the pituitary,adrenal, thyroid, and testes. Thus, specific endocrine rhythmsare affected by alterations in trophic hormone secretion bythe hypothalamus-pituitary complex, direct effects on biochemicaltransformations within target organs, or by alterations in metabolismand excretion of hormones by the liver. Target enzymes commonto the above organs for melatonin and arginine vasotocin (AVT)are 5-reductase, monoamine oxidase (MAO), and smooth muscleenzymes. Melatonin selectively inhibited 17rß ol-dehydrogenaseactivity and 5-reductase activity while 17rß ol-dehydrogenasewas stimulated by serotonin (5-HT). Other steroid biotransformationswere inhibited by both 5-HT and melatonin. Evidence from thepancreas and insulin secretion, liver and glucuronosyl transferaseactivity, and hypothalamic and pituitary studies indicate thatmelatonin mediated some of its effects on these organs throughMAO activity and 5-HT levels. There were some species and tissuedifferences with respect to the effects of melatonin and AVTon MAO activity and steroid biotransformations. Melatonin stimulatedsteroid biotransformations in the duck, while MAO activity and5-reductase activity in the hamster responded differently tomelatonin than did similar preparations from the rat.     

Steroid-protein interaction in human placenta

Human placenta produces a large variety of bioactive substances with endocrine and neural competence: pituitary and gonadal hormones, hypothalamic-like releasing or inhibiting hormones, growth factors, cytokines and neuropeptides. The most recent findings indicate that locally produced hormones regulate the secretion of other placental hormones supporting a paracrine/autocrine regulation. In placental endocrinology, a particular relevance is played by steroid hormones. In fact, a specific gonadotropin-releasing hormone (GnRH)-human chorionic gonadotropin (hCG) regulation of placental steroidogenesis has been proposed as a placental internal regulatory system acting on steroids production from human placenta. In addition, activin and inhibin have been proposed as further regulatory substances of the synthesis and secretion of steroids; the addition of activin A to placental culture augments GnRH, hCG and progesterone, and this effect can be significantly reduced by the addition of inhibins. Finally, a steroid-steroid interaction is suggested by the evidence that placental estrogen has a positive role in the regulation of progesterone biosynthesis. Other steroid-protein interactions have been observed in human placenta. In fact, recent data indicate that progesterone inhibits placental corticotropin-releasing factor (CRF) and estrogens act on placental conversion of cortisol to cortisone, activating cortisol secretion by the fetal adrenal and enhancing fetal adrenal function with advancing gestation.     

Steroid hormones regulate programmed cell death: a review

Programmed cell death (PCD) is a physiologically active process which is essential for the proper functioning of any living tissue. The steroid hormones modulate the programme in the immunological and reproductive organs and tissues, such as the thymus gland, circulating thymocytes, uterus, vagina, testis, ovary and prostrate gland. The influence of steroid hormones on cell death is tissue specific; the same hormone can inhibit PCD in one tissue, and may promote PCD in another tissue. The roles of apoptosis and terminal differentiation have been examined, and the regulation of PCD by steroid hormones, assessed.     

Modulation of the hypothalamo-pituitary-gonadal axis and the pineal gland by neurokinin A, neuropeptide K and neuropeptide gamma.

Modulation of the hypothalamo-pituitary-gonadal axis and the pineal gland by neurokinin A, neuropeptide K, and neuropeptide gamma. PEPTIDES 1999. Neurokinin A (NKA), neuropeptide K (NPK) and neuropeptide gamma (NPG) are members of the family of tachykinins, and act preferentially on NK-2 tachykinin receptors. These peptides are widely distributed and are potent stimulators of smooth muscle contraction, especially in the respiratory and gastrointestinal tract. They also induce vasodilatation and plasma extravasation. Through their effects on the vascular tone, they are also potential regulators of the blood flow and therefore of the function of many organs and tissues. Tachykinins have been demonstrated to influence the secretory activity of endocrine cells, and they may have a physiological role as regulators of endocrine functions. A number of reports have indicated that NPK, NKA and NPG act on the hypothalamo-pituitary gonadal axis to regulate functions related to reproduction. Therefore, we thought that, at this point, it was important to review the available evidence suggesting the role of these tachykinins on reproductive functions by effects exerted at 3 different levels of regulation: the hypothalamus, the anterior pituitary and the gonads. These 3 tachykinin peptides were reported to have effects on reproductive functions, acting on the control of the secretion of gonadotropin and prolactin at the level of the hypothalamo-pituitary axis, and on the steroid secretion by the testes and the ovaries. Acting on the hypothalamus, tachykinins, mainly NPK, were reported to inhibit LH secretion, but this effect is dependent on the presence of gonadal steroids. On the anterior pituitary gland, however, tachykinins were shown to stimulate LH and prolactin secretion, and this effect is also dependent on the presence of gonadal steroids. Tachykinin concentrations in the hypothalamus and pituitary are regulated by steroid hormones. In the hypothalamus, estrogens and testosterone increase tachykinin concentration. In the anterior pituitary gland, estradiol and thyroid hormones markedly depress tachykinin concentrations. Ovariectomy and exposure to short photoperiods significantly increase anterior pituitary tachykinins in the Siberian hamster. In the pineal gland, SP and NK-1 receptors are present and, more recently, the presence of NKA and probably also NPK was demonstrated. Castration and steroid replacement modified the content of tachykinins in the pineal gland. The removal of the superior cervical ganglia was followed by an increase in NKA content in the pineal gland. These results suggest that gonadal steroids may influence tachykinins in the pineal gland. In the gonads, tachykinins stimulated the secretory activity of Sertoli cells, but inhibited testosterone secretion by Leydig cells. There are very few reports on the role of tachykinins in the ovary, but some of them indicated that these peptides are present in some of the ovarian structures, and they may affect the secretion of ovarian steroids. Thus, NKA, NPK and NPG appear to have a modulatory role, mainly acting as paracrine factors, on the hypothalamo-pituitary-gonadal axis.     

Effects of Estradiol and Testosterone in the Hagfish Eptatretus burgeri

Effects of exogenous estradiol and testosterone on the gonad and pituitary were examined in the hagfish. Estradiol caused degeneration of the ovary. Testosterone had no effect on the ovary. Neither steroid had a significant effect on the testis. Neither estradiol nor testosterone provoked a conspicuous change in adenohypophysial cells. Therefore, a feedback mechanism between gonadal steroids and gonadotropin either does not exist or plays a very minor role. The degeneration of the ovary may be due to a pharmacological effect of estradiol.     

Secretogranin II: Relative Amounts and Processing to Secretoneurin in Various Rat Tissues

Abstract: Secretoneurin is a 33-amino-acid peptide produced in vivo from secretogranin II. An antiserum raised against this peptide recognizes both the free peptide and its precursors. By HPLC and radioimmunoassay we characterized the immunoreactive molecules and determined the levels of immunoreactivity in various rat organs. In adrenal medulla and to a lesser degree in the anterior pituitary processing of secretogranin II to secretoneurin was very limited, whereas in all other organs studied (brain, intestine, endocrine pancreas, thyroid gland, and posterior pituitary) a high degree of processing was apparent. Thus, practically all of the immunoreactivity was present as free secretoneurin. This was also true for serum. When the total amount of secretoneurin immunoreactivity was calculated for the various organs, the largest pools in descending order were in the intestine, CNS, anterior pituitary, pancreas, and adrenal gland. This makes it likely that secretoneurin in serum is mainly derived from the intestine. The high degree of processing of secretogranin II in most organs is consistent with the concept that this protein acts as a precursor of a functional peptide, i.e., secretoneurin.     

Expression and tissue localization of renalase, a novel soluble FAD-dependent protein, in reproductive/steroidogenic systems

Renalase was initially identified in human kidney as a soluble monoamine oxidase. Here we show that renalase is predominantly expressed in reproductive/steroidogenic systems, with particularly substantial expression in oocytes, granulosa, interstitial and luteal cells of ovary, spermatogenic cells of testis, and cortex of adrenal gland, suggesting its function(s) in maturation of germ cells and steroid hormone regulation. Renalase expression increases in testes and ovaries as mice develop and its expression is further enhanced in the ovaries of pregnant mice, indicating an activity of renalase in reproduction. Gonadotropin-releasing hormone (GnRH) antagonist, cetrorelix, repressed renalase expression in mice ovaries and testes, suggesting that steroids regulate renalase expression. Leptin is an effector and modulator of steroid hormones and reproduction. Surprisingly, knockout of leptin causes a dramatic increase of renalase expression in mice testes. Taken together, our results suggest that reproductive/steroidogenic systems are also the sources for renalase secretion and renalase may play a critical role in reproduction and hormone regulation. This provides a novel insight into understanding the function of renalase.     

Thymic hormone containing cells--IX. Steroids in vitro modulate thymulin secretion by human and murine thymic epithelial cells

We investigated the in vitro effects (kinetics and dose-response) of adrenal and sexual steroid hormones on the secretion of thymulin, a thymic hormone, by human thymic epithelial cells in primary cultures as well as in a rat epithelial cell line. We demonstrated that all steroids tested, in a range of physiological doses, stimulated thymulin production to various extents. Progesterone and estradiol, however, were revealed to be the most efficient. Specific steroid antagonists abrogated the steroid-induced stimulation of thymulin production. These findings confirm our previous in vivo results and demonstrate that steroid hormones can act directly on thymic epithelial cells to modulate their endocrine production.     

3β-Hydroxysteroid dehydrogenaseΔ5−4isomerase activity in the rhesus monkey placenta and fetal adrenal,testis and ovary during late gestation

3β-Hydroxysteroid $\text{dehydrogenase}\text{Δ}{}^{\mathrm{5?4}}\text{isomerase}$ (3β-HSDH) was measured in the rhesus monkey ($\text{Macaca mulatta}$) placenta, fetal adrenal (whole organ minus medulla), testis and ovary during late gestation (Days 145–162). Activities were evaluated from the conversion of [³H]-pregnenolone to [³H]progesterone. The maximum enzyme velocity (V_m) in adrenal microsomes (100,000 g pellet) was significantly higher (146 nmoles progesterone/h x mg^?1protein) than in microsomes from the other tissues. Testicular V_m was greater than either ovarian or placental V_m which were not different from one another (11.5 versus 1.9, 1.2 nmoles progesterone/h x mg^?1protein, respectively). Apparent Michaelis-Menten constants in the adrenal, placenta, testis and ovary averaged 1.8,2.5,0.27 and 0.16 μM, respectively. In some cases, substrate inhibition was noted. Estimated dissociation constants for pregnenolone were 2.3 μM (adrenal), 2.1 μM (placenta), 0.74 μM (testis) and 0.13 μM (ovary). 3β-HSDH was less active in a crude mitochondrial preparation from the fetal adrenal (10,000 g pellet) than in microsomes, whereas activity in the placenta and testis appeared to be equally distributed between mitochrondria and microsomes.Rate measurements were consistent with the apparent potentials of these organs to synthesize their characteristic hormones. Thus, 3β-HSDH activity may be an important rate determining step in hormone synthesis. The importance of substrate inhibition in progesterone formation remains to be assessed.