Retroperitoneal Solid Pseudopapillary Tumor Mimicking Adrenal Malignant Tumor in a 67-Year-Old Man.

Solid pseudopapillary tumor (SPT) is a low-grade malignant tumor of the pancreas. SPT typically affects women and can occur in ectopic pancreatic region; however, it also occurs rarely in retroperitoneum. The tumor may be bulky at the time of diagnosis since there is no specific clinical manifestation. Here we present an older male case with retroperitoneal SPT. A 67-year-old man consulted for intermittent fever and lumbago. His basal hormonal profile screened out a functional tumor. Computed tomography (CT) showed a gigantic mass in his left adrenal region. A normal left adrenal gland was not identified, and the tumor's feeding artery was recognized as the left adrenal artery by the contrast-enhanced CT. Adrenal malignant tumor was suspected, and tumor resection was performed. The resected tumor size was 15 × 10 × 9 cm. Histologically, epithelial-like cells with round nuclei and a small amount of eosinophilic cytoplasm proliferated in papillary (around the blood vessels) or uniformly solid form. By immunostaining, tumor cells were vimentin, CD56, cytokeratin AE1/AE3, CD10, ß-catenin in the nucleus, cyclin D1, and PgR positive. These findings led to the diagnosis of SPT. Although rare, SPT should be considered as a differential diagnosis in cases of a mass arising from the adrenal region.

[The Tips of the Endocrine Assessment in the Case of Pituitary Tumor].

Pituitary tumors can cause an excess or deficiency of anterior pituitary hormones. Functional pituitary neuroendocrine tumors(PitNETs)include growth hormone(GH)-producing tumors, adrenocorticotropic hormone(ACTH)-producing tumors, thyroid-stimulating hormone(TSH)-producing tumors, and prolactin(PRL)-producing tumors. Comprehensive preoperative endocrine evaluation is essential for appropriate therapeutic decision-making and safe surgery. Here, we focus on the diagnosis and evaluation of PitNETs using endocrine function tests and intravascular catheterization for inferior petrosal sinus sampling for pituitary tumors.

Masked CKD in hyperthyroidism and reversible CKD status in hypothyroidism.

Introduction: While it is well known that thyroid function may affect kidney function, the transition of the chronic kidney disease (CKD) status before and after treatment for thyroid disorders, as well as the factors affecting this change, remains to be explored. In the present study, we focused on the change in kidney function and their affecting factors during the treatment for both hyperthyroidism and hypothyroidism. Methods: Eighty-eight patients with hyperthyroidism and fifty-two patients with hypothyroidism were enrolled in a retrospective and longitudinal case series to analyze the changes in kidney function and their affecting factors after treatment for thyroid disorders. Results: Along with the improvement of thyroid function after treatment, there was a significant decrease in estimated glomerular filtration rate (eGFR) in hyperthyroidism (an average ΔeGFR of -41.1 mL/min/1.73 m2) and an increase in eGFR in hypothyroidism (an average ΔeGFR of 7.1 mL/min/1.73 m2). The multiple linear regression analysis revealed that sex, eGFR, free thyroxine (FT4) and free triiodothyronine (FT3) could be considered independent explanatory variables for ΔeGFR in hyperthyroidism, while age, eGFR, and FT3 were detected as independent explanatory variables in hypothyroidism. In addition, the stratification by kidney function at two points, pre- and post-treatment for thyroid disorders, revealed that 4.5% of the participants with hyperthyroidism were pre-defined as non-CKD and post-defined as CKD, indicating the presence of "masked" CKD in hyperthyroidism. On the other hand, 13.5% of the participants with hypothyroidism presented pre-defined CKD and post-defined non-CKD, indicating the presence of "reversible" CKD status in hypothyroidism. Conclusions: We uncovered the population of masked CKD in hyperthyroidism and reversible CKD status in hypothyroidism, thereby re-emphasizing the importance of a follow-up to examine kidney function after treatment for hyperthyroidism and the routine evaluation of thyroid function in CKD patients as well as the appropriate hormone therapy if the patient has hypothyroidism.

Effects of Wnt-ß-Catenin Signaling and Sclerostin on the Phenotypes of Rat Pheochromocytoma PC12 Cells.

Pheochromocytomas and paragangliomas (PPGLs) are classified into 3 major categories with distinct driver genes: pseudohypoxia, kinase signaling, and Wnt-altered subtypes. PPGLs in the Wnt-altered subtype are sporadic and tend to be aggressive with metastasis, where somatic gene fusions affecting mastermind-like 3 (MAML3) and somatic mutations in cold shock domain containing E1 (CSDE1) cause overactivation of Wnt-ß-catenin signaling. However, the relation between Wnt-ß-catenin signaling and the biological behavior of PPGLs remains unexplored. In rat pheochromocytoma PC12 cells, Wnt3a treatment enhanced cell proliferation and suppressed mRNA expression of tyrosine hydroxylase (TH), the rate-limiting enzyme of catecholamine biosynthesis, and dopamine secretion. We identified the expression of sclerostin in PC12 cells, which is known as an osteocyte-derived negative regulator for Wnt signaling-driven bone formation. Inhibition of endogenous Wnt pathway by XAV939 or sclerostin resulted in attenuated cell proliferation and increased TH expression. Furthermore, Wnt3a pretreatment suppressed bone morphogenetic protein (BMP)-induced Smad1/5/9 phosphorylation whereas BMPs enhanced sclerostin expression in PC12 cells. In the Wnt-altered subtype, the increased Wnt-ß-catenin pathway may contribute the aggressive clinical behavior with reduced catecholamine production. Furthermore, upregulated expression of sclerostin by BMPs may explain the osteolytic metastatic lesions observed in metastatic PPGLs.

Androgen Suppresses In Vivo and In Vitro LH Pulse Secretion and Neural Kiss1 and Tac2 Gene Expression in Female Mice.

Androgens can affect the reproductive axis of both sexes. In healthy women, as in men, elevated exogenous androgens decrease gonad function and lower gonadotropin levels; such circumstances occur with anabolic steroid abuse or in transgender men (genetic XX individuals) taking androgen supplements. The neuroendocrine mechanisms by which endogenous or exogenous androgens regulate gonadotropin release, including aspects of pulsatile luteinizing hormone (LH) secretion, remain unknown. Because animal models are valuable for interrogating neural and pituitary mechanisms, we studied effects of androgens in the normal male physiological range on in vivo LH secretion parameters in female mice and in vitro LH secretion patterns from isolated female pituitaries. We also assessed androgen effects on hypothalamic and gonadotrope gene expression in female mice, which may contribute to altered LH secretion profiles. We used a nonaromatizable androgen, dihydrotestosterone (DHT), to isolate effects occurring specifically via androgen receptor (AR) signaling. Compared with control females, DHT-treated females exhibited markedly reduced in vivo LH pulsatility, with decreases in pulse frequency, amplitude, peak, and basal LH levels. Correlating with reduced LH pulsatility, DHT-treated females also exhibited suppressed arcuate nucleus Kiss1 and Tac2 expression. Separate from these neural effects, we determined in vitro that the female pituitary is directly inhibited by AR signaling, resulting in lower basal LH levels and reduced LH secretory responses to gonadotropin-releasing hormone pulses, along with lower gonadotropin gene expression. Thus, in normal adult females, male levels of androgen acting via AR can strongly inhibit the reproductive axis at both the neural and pituitary levels.

GLUT1-mediated glycolysis supports GnRH-induced secretion of luteinizing hormone from female gonadotropes.

The mechanisms mediating suppression of reproduction in response to decreased nutrient availability remain undefined, with studies suggesting regulation occurs within the hypothalamus, pituitary, or gonads. By manipulating glucose utilization and GLUT1 expression in a pituitary gonadotrope cell model and in primary gonadotropes, we show GLUT1-dependent stimulation of glycolysis, but not mitochondrial respiration, by the reproductive neuropeptide GnRH. GnRH stimulation increases gonadotrope GLUT1 expression and translocation to the extracellular membrane. Maximal secretion of the gonadotropin Luteinizing Hormone is supported by GLUT1 expression and activity, and GnRH-induced glycolysis is recapitulated in primary gonadotropes. GLUT1 expression increases in vivo during the GnRH-induced ovulatory LH surge and correlates with GnRHR. We conclude that the gonadotropes of the anterior pituitary sense glucose availability and integrate this status with input from the hypothalamus via GnRH receptor signaling to regulate reproductive hormone synthesis and secretion.

SRXN1 Is Necessary for Resolution of GnRH-Induced Oxidative Stress and Induction of Gonadotropin Gene Expression.

A defining characteristic of the hypothalamus-pituitary-gonad reproductive endocrine axis is the episodic secretion of the pituitary gonadotropin hormones LH and FSH by the anterior pituitary gonadotropes. Hormone secretion is dictated by pulsatile stimulation, with GnRH released by hypothalamic neurons that bind and activate the G protein-coupled GnRH receptor expressed by gonadotropes. Hormone secretion and synthesis of gonadotropins are influenced by the amplitude and frequency of GnRH stimulation; variation in either affects the proportion of LH and FSH secreted and the differential regulation of hormone subunit gene expression. Therefore, proper decoding of GnRH signals is essential for appropriate gonadotropin synthesis and secretion. The GnRH receptor robustly activates downstream signaling cascades to facilitate exocytosis and stimulate gene expression and protein synthesis. It is necessary to rapidly quench signaling to preserve sensitivity and adaptability to changing pulse patterns. Reactive oxygen species (ROS) generated by receptor-activated oxidases fulfill the role of rapid signaling intermediates that facilitate robust and transient signaling. However, excess ROS can be detrimental and, unchecked, can confuse signal interpretation. We demonstrate that sulfiredoxin (SRXN1), an ATP-dependent reductase, is essential for normal responses to GnRH receptor signaling and plays a central role in resolution of ROS induced by GnRH stimulation. SRXN1 expression is mitogen-activated protein kinase dependent, and knockdown reduces Lhb and Fshb glycoprotein hormone subunit mRNA and promoter activity. Loss of SRXN1 leads to increased basal and GnRH-stimulated ROS levels. We conclude that SRXN1 is essential for normal responses to GnRH stimulation and plays an important role in ROS management.

The RNA-Binding Protein ELAVL1 Regulates GnRH Receptor Expression and the Response to GnRH.

Gonadotropin secretion, which is elicited by GnRH stimulation of the anterior pituitary gonadotropes, is a critical feature of reproductive control and the maintenance of fertility. In addition, activation of the GnRH receptor (GnRHR) regulates transcription and translation of multiple factors that regulate the signaling response and synthesis of gonadotropins. GnRH stimulation results in a broad redistribution of mRNA between active and inactive polyribosomes within the cell, but the mechanism of redistribution is not known. The RNA-binding protein embryonic lethal, abnormal vision, Drosophila-like 1 (ELAVL1) binds to AU-rich elements in mRNA and is one of the most abundant mRNA-binding proteins in eukaryotic cells. It is known to serve as a core component of RNA-binding complexes that direct the fate of mRNA. In LßT2 gonadotropes, we showed that ELAVL1 binds to multiple mRNAs encoding factors that are crucial for gonadotropin synthesis and release. Association with some mRNAs is GnRH sensitive but does not correlate with abundance of binding. We also showed MAPK-dependent changes in intracellular localization of ELAVL1 in response to GnRH stimulation. Knockdown of ELAVL1 gene expression resulted in reduced Lhb and Gnrhr mRNA levels, reduced cell surface expression of GnRHR, and reduced LH secretion in response to GnRH stimulation. Overall, these observations not only support the role of ELAVL1 in GnRHR-mediated regulation of gene expression and LH secretion but also indicate that other factors may contribute to the precise fate of mRNA in response to GnRH stimulation of gonadotropes.

Induction of Stress Signaling In Vitro and Suppression of Gonadotropin Secretion by Free Fatty Acids in Female Mouse Gonadotropes.

An emerging body of evidence supports the concept that the pituitary is a site for integration of multiple physiological and metabolic signals that inform and modulate endocrine pathways. Multiple endocrine mediators of energy balance and adiposity are known to impinge on the neuroendocrine axis regulating reproduction. Observations in humans show that obesity is correlated with decreased gonadotropin secretion, and studies have also suggested that pituitary sensitivity to stimulation by gonadotropin-releasing hormone (GnRH) is decreased in obese individuals. Free fatty acids are a potential mediator of adiposity and energy balance, but their impact as an endocrine modulator of pituitary function has not been closely examined. We evaluated the impact of free fatty acids on a pituitary gonadotrope cell line and in primary pituitary cultures of female mice. We show that increasing physiologically relevant doses of the monounsaturated ω-9 fatty acid oleate induces cellular stress and increases production of reactive oxygen species in a mouse gonadotrope cell line. In contrast, the unsaturated ω-3 α-linolenic and ω-6 linoleic fatty acids do not have this effect. Additionally, oleate can activate immediate-early gene expression independent of GnRH stimulation but has a negative impact on GnRH induction and expression of the gonadotropin subunit gene Lhb. Further, oleate suppresses gonadotropin secretion in response to pulsatile stimulation by GnRH. These results indicate that free fatty acids can directly alter gonadotropin gene expression and secretion in response to GnRH and may provide a link between energy sensing and reproduction.

Reactive Oxygen Species Link Gonadotropin-Releasing Hormone Receptor Signaling Cascades in the Gonadotrope.

Biological rhythms lie at the center of regulatory schemes that control many aspects of living systems. At the cellular level, meaningful responses to external stimuli depend on propagation and quenching of a signal to maintain vigilance for subsequent stimulation or changes that serve to shape and modulate the response. The hypothalamus-pituitary-gonad endocrine axis that controls reproductive development and function relies on control through rhythmic stimulation. Central to this axis is the pulsatile stimulation of the gonadotropes by hypothalamic neurons through episodic release of the neuropeptide gonadotropin-releasing hormone. Alterations in pulsatile stimulation of the gonadotropes result in differential synthesis and secretion of the gonadotropins LH and FSH and changes in the expression of their respective hormone subunit genes. The requirement to amplify signals arising from activation of the gonadotropin-releasing hormone (GnRH) receptor and to rapidly quench the resultant signal to preserve an adaptive response suggests the need for rapid activation and feedback control operating at the level of intracellular signaling. Emerging data suggest that reactive oxygen species (ROS) can fulfill this role in the GnRH receptor signaling through activation of MAP kinase signaling cascades, control of negative feedback, and participation in the secretory process. Results obtained in gonadotrope cell lines or other cell models indicate that ROS can participate in each of these regulatory cascades. We discuss the potential advantage of reactive oxygen signaling for modulating the gonadotrope response to GnRH stimulation and the potential mechanisms for this action. These observations suggest further targets of study for regulation in the gonadotrope.

The Clinical and Hormonal Characteristics of Primary Adrenal Lymphomas: The Necessity of Early Detection of Adrenal Insufficiency.

Objective To analyze the clinical and endocrine characteristics of patients with primary adrenal lymphoma. Patients We retrospectively reviewed the cases of five patients with primary adrenal lymphoma who were treated in our hospital between April 2004 and March 2015. We investigated the characteristics of the clinical and pathological findings, treatment, prognosis and complications of adrenal insufficiency. Results Adrenal insufficiency, which was confirmed by the laboratory data at the initial presentation, was observed in two cases. One case was complicated by relative adrenal insufficiency during a course of chemotherapy. The plasma adrenaline and urinary adrenaline levels were decreased in four cases and three cases, respectively. Diffusion MRI was radiologically diagnostic. In all of the cases, the patients were pathologically diagnosed with diffuse large-B cell lymphoma and were treated with rituximab and CHOP (cyclophosphamide, doxorubicin, vincristine and prednisone)-like chemotherapy. Two patients received central nervous system prophylaxis with high-dose methotrexate. Four of the patients survived and one patient died during the follow-up period. Conclusion The early detection of adrenal insufficiency and the administration of an appropriate dose of hydrocortisone are necessary during the course of chemotherapy as well as at the initial manifestation. The exclusion of adrenal dysfunction prior to invasive diagnostic procedures, such as CT-guided needle biopsy, is also critical.

Combined Effects of Androgen and Growth Hormone on Osteoblast Marker Expression in Mouse C2C12 and MC3T3-E1 Cells Induced by Bone Morphogenetic Protein.

Osteoblasts undergo differentiation in response to various factors, including growth factors and steroids. Bone mass is diminished in androgen- and/or growth hormone (GH)-deficient patients. However the functional relationship between androgen and GH, and their combined effects on bone metabolism, remains unclear. Here we investigated the mutual effects of androgen and GH on osteoblastic marker expression using mouse myoblastic C2C12 and osteoblast-like MC3T3-E1 cells. Combined treatment with dihydrotestosterone (DHT) and GH enhanced BMP-2-induced expression of Runx2, ALP, and osteocalcin mRNA, compared with the individual treatments in C2C12 cells. Co-treatment with DHT and GH activated Smad1/5/8 phosphorylation, Id-1 transcription, and ALP activity induced by BMP-2 in C2C12 cells but not in MC3T3-E1 cells. The insulin-like growth factor (IGF-I) mRNA level was amplified by GH and BMP-2 treatment and was restored by co-treatment with DHT in C2C12 cells. The mRNA level of the IGF-I receptor was not significantly altered by GH or DHT, while it was increased by IGF-I. In addition, IGF-I treatment increased collagen-1 mRNA expression, whereas blockage of endogenous IGF-I activity using an anti-IGF-I antibody failed to suppress the effect of GH and DHT on BMP-2-induced Runx2 expression in C2C12 cells, suggesting that endogenous IGF-I was not substantially involved in the underlying GH actions. On the other hand, androgen receptor and GH receptor mRNA expression was suppressed by BMP-2 in both cell lines, implying the existence of a feedback action. Collectively the results showed that the combined effects of androgen and GH facilitated BMP-2-induced osteoblast differentiation at an early stage by upregulating BMP receptor signaling.

The possible involvement of intestine-derived IgA1: a case of IgA nephropathy associated with Crohn's disease.

BACKGROUND: A link between IgA nephropathy and Crohn's disease has recently been reported. Other researchers hypothesize that intestine-derived IgA complexes deposit in glomerular mesangial cells, eliciting IgA nephropathy. Intestinal mucosal plasma cells mainly secrete IgA2. Nevertheless, IgA1 deposition is strongly implicated as being the primary cause of IgA nephropathy. CASE PRESENTATION: A 46-year-old Japanese man developed IgA nephropathy 29 years ago, following tonsillectomy. As a result, a normal urinalysis was obtained. The patient previously suffered Crohn's disease followed by urinary occult blood and proteinuria six years ago. Exacerbation of IgA nephropathy was highly suspected. Therefore a renal biopsy was performed. A diagnosis of exacerbation of IgA nephropathy with mesangial cell proliferation and fibrotic cellular crescent was based upon the pathological findings. The patient exhibited a positive clinical course and eventually achieved a remission with immunosuppressive therapy including prednisolone treatment. Immunostaining for the detection of IgA subtypes was performed on both of his kidney and excised ileum. The results revealed IgA1 and IgA2 deposition by submucosal cells in intestine. Furthermore, IgA1 deposition of mesangial areas in the patient's kidney, indicated an association of IgA1 with the exacerbation of IgA nephropathy. CONCLUSION: This case represents the possibility that the intestine-derived IgA1 can be the origin of galactose-deficient IgA which is known to cause IgA nephropathy exacerbation.

[A Case of an Adrenocorticotropic Hormone-Producing Pituitary Adenoma Removed via Electromagnetic-Guided Neuroendoscopy].

The use of navigation systems is safe and reliable for neurological surgery. We performed endoscopic transsphenoidal surgery to totally resect an adrenocorticotropic hormone (ACTH)-producing pituitary adenoma associated with oculomotor nerve palsy. A 70-year-old woman developed right ptosis 4 months before admission. She developed anisocoria 2 months later and was referred to the department of neurology from clinic. Brain magnetic resonance imaging(MRI)showed an intrasellar tumor that partially invaded the right cavernous sinus, and she was then referred to our department. She exhibited a round face ("moon face") and central obesity. Laboratory test results showed a high urinary cortisol level and high serum ACTH level, and neither the serum cortisol nor ACTH level was suppressed by a low-dose dexamethasone test. We performed transsphenoidal surgery using high-dimensional endoscopy under electromagnetic navigation. The tumor invading the cavernous sinus was visualized via endoscopy and confirmed on navigation using a flexible needle probe. Postoperative MRI showed total removal of the tumor, and the serum ACTH level recovered to the normal range. The patient's right oculomotor palsy resolved within 1 week postoperatively. In summary, electromagnetic navigation was useful for total resection of a pituitary tumor invading the cavernous sinus, contributing to normalization of the ACTH level and improvement in neurological symptoms.

BMP-6 modulates somatostatin effects on luteinizing hormone production by gonadrotrope cells.

The effects of somatostatin analogs and roles of BMP-6 in the regulation of luteinizing hormone (LH) secretion were investigated using mouse gonadotrope LßT2 cells. LH mRNA expression and LH secretion induced by GnRH were suppressed by treatments with somatostatin analogs, including octreotide and pasireotide, in LßT2 cells. Of note, the inhibitory effects of somatostatin analogs on LH secretion were enhanced by the action of BMP-6. BMP-6 increased the expression levels of somatostatin receptor (SSTR)5, suggesting that BMP-6 upregulates SSTR activity that leads to reduction of GnRH-induced LH secretion. In addition, GnRH-induced phosphorylation of MAPKs including ERK, but not P38 or SAPK, was suppressed by pasireotide in the presence of BMP-6. Given that each inhibitor of ERK, JNK or P38 signaling suppressed GnRH-induced LH transcription, MAPKs are individually involved in the induction of LH production by LßT2 cells. Somatostatin analogs also impaired BMP-6-induced Smad1/5/8 phosphorylation by suppressing BMPRs and augmenting Smad6/7 expression. Collectively, the results indicate that somatostatin analogs have dual effects on the modulation of GnRH-induced MAPK signaling and BMP activity. The pituitary BMP system may play a regulatory role in GnRH-induced LH secretion by tuning the responsiveness to somatostatin analogs in gonadotrope cells.

Regulatory effects of fibroblast growth factor-8 and tumor necrosis factor-α on osteoblast marker expression induced by bone morphogenetic protein-2.

BMP induces osteoblast differentiation, whereas a key proinflammatory cytokine, TNF-α, causes inflammatory bone damage shown in rheumatoid arthritis. FGF molecules are known to be involved in bone homeostasis. However, the effects of FGF-8 on osteoblast differentiation and the interaction between FGF-8, BMPs and TNF-α have yet to be clarified. Here we investigated the effects of FGF-8 in relation to TNF-α actions on BMP-2-induced osteoblast marker expression using myoblast cell line C2C12, osteoblast precursor cell line MC3T3-E1 and rat calvarial osteoblasts. It was revealed that FGF-8 inhibited BMP-2-induced expression of osteoblast differentiation markers, including Runx2, osteocalcin, alkaline phosphatase, type-1 collagen and osterix, in a concentration-dependent manner. The inhibitory effects of FGF-8 on BMP-induced osteoblast differentiation and Smad1/5/8 activation were enhanced in the presence of TNF-α action. FGF-8 also inhibited BMP-2-induced expression of Wnt5a, which activates a non-canonical Wnt signaling pathway. FGF-8 had no significant influence on the expression levels of TNF receptors, while FGF-8 suppressed the expression of inhibitory Smad6 and Smad7, suggesting a possible feedback activity through FGF to BMP receptor (BMPR) signaling. Of note, inhibition of ERK activity and FGF receptor (FGFR)-dependent protein kinase, but not JNK or NFκB pathway, suppressed the FGF-8 actions on BMP-induced osteoblast differentiation. FGF-8 was revealed to suppress BMP-induced osteoblast differentiation through the ERK pathway and the effects were enhanced by TNF-α. Given the finding that FGF-8 expression was increased in synovial tissues of rheumatoid arthritis, the functional interaction between FGFR and BMPR signaling may be involved in the development process of inflammatory bone damage.

Mutual effects of melatonin and activin on induction of aldosterone production by human adrenocortical cells.

Melatonin has been reported to suppress adrenocorticotropin (ACTH) secretion in the anterior pituitary and cortisol production in the adrenal by different mechanisms. However, the effect of melatonin on aldosterone production has remained unknown. In this study, we investigated the role of melatonin in the regulation of aldosterone production using human adrenocortical H295R cells by focusing on the activin system expressed in the adrenal. Melatonin receptor MT1 mRNA and protein were expressed in H295R cells and the expression levels of MT1 were increased by activin treatment. Activin increased ACTH-induced, but not angiotensin II (Ang II)-induced, aldosterone production. Melatonin alone did not affect basal synthesis of either aldosterone or cortisol. However, melatonin effectively enhanced aldosterone production induced by co-treatment with ACTH and activin, although melatonin had no effect on aldosterone production induced by Ang II in combination with activin. These changes in steroidogenesis became apparent when the steroid production was evaluated by the ratio of aldosterone/cortisol. Melatonin also enhanced dibutyryl-AMP-induced aldosterone/cortisol levels in the presence of activin, suggesting a functional link to the cAMP-PKA pathway for induction of aldosterone production by melatonin and activin. In accordance with the data for steroids, ACTH-induced, but not Ang II-induced, cAMP synthesis was also amplified by co-treatment with melatonin and activin. Furthermore, the ratio of ACTH-induced mRNA level of CYP11B2 compared with that of CYP17 was amplified in the condition of treatment with both melatonin and activin. In addition, melatonin increased expression of the activin type-I receptor ALK-4 but suppressed expression of inhibitory Smads6/7, leading to the enhancement of Smad2 phosphorylation. Collectively, the results showed that melatonin facilitated aldosterone production induced by ACTH and activin via the cAMP-PKA pathway. The results also suggested that mutual enhancement of melatonin and activin receptor signaling is involved in the induction of aldosterone output by adrenocortical cells.