[Physicochemical characteristics of salusin-beta and establishment of the radioimmunoassay]

Salusin-beta is a 20 amino acid bioactive peptide originally identified using bioinformatic analyses of human full-length enriched cDNA library. Salusin-beta has been shown to exert potent hypotensive, bradycardic, and pro-atherosclerotic effects. The form in which it exists in biological fluids remained undetermined due to technical difficulties originating from its unexpected physicochemical properties. Salusin-beta peptide adheres to polypropylene, glass and polystyrene, so that the aliquoted peptide dissolved in distilled water may rapidly disappear from the dissolved solution. Strategies to circumvent such problems in biological experiments include use of low doses of NP-40 or Tween-20 which alleviates its adhesiveness. Addition of 0.1% of NP-40 to the radioimmunoassay buffer markedly reduced non-specific binding of both labeled and unlabeled salusin-beta to the assay tubes without interfering the binding of salusin-beta to its antibody. Successful establishment of a specific radioimmunoassay suitable for detection of immunoreactive human salusin-beta allowed to characterize the molecular form of salusin-beta released from a human-derived cultured cell line.

The (pro)renin receptor is cleaved by ADAM19 in the Golgi leading to its secretion into extracellular space

The (pro)renin receptor ((P)RR), which is a recently discovered molecule of the renin-angiotensin system, plays an important role in the development of cardiovascular diseases. However, the molecular properties and the subcellular distribution of (P)RR remain controversial. In this study, (P)RR-Venus in Chinese hamster ovary (CHO) cells ((P)RR-Venus-CHO) or endogenous (P)RR in human vascular smooth muscle cells (VSMC) were constitutively cleaved without any stimulation, and secretion of the amino-terminal fragment (NTF-(P)RR) into the media was determined using western blot analysis. Immunofluorescent analysis showed robust expression of (P)RR in the endoplasmic reticulum (ER) or the Golgi but not in the plasma membrane. Moreover, we identified ADAM19, which is expressed in the Golgi, as one of cleaving proteases of (P)RR. Transfected ADAM19 evoked the shedding of (P)RR, whereas transfected dominant negative ADAM19 suppressed it. Although (P)RR contains a furin cleavage site, neither the furin-deficient LoVo cells nor furin inhibitor-treated VSMC lost NTF-(P)RR in the media. The secreted NTF-(P)RR induced the renin activity of prorenin in the extracellular space. We describe that (P)RR is mainly localized in the subcellular organelles, such as the ER and Golgi, and (P)RR is cleaved by ADAM19 in the Golgi resulting in two fragments, NTF-(P)RR and CTF-(P)RR. These results may suggest that (P)RR is predominantly secreted into the extracellular space.

A woman with salt-wasting congenital adrenal hyperplasia presenting with a mucinous ovarian cystadenoma during pregnancy

Women with congenital adrenal hyperplasia (CAH) caused by steroid 21-hydroxylase deficiency show reduced fertility, especially with the salt-wasting form. A 27-year-old pregnant woman with this disease underwent laparotomy and oophorectomy to remove a multilocular ovarian tumor at 14 weeks of pregnancy. This proved to be a mucinous cystadenoma. Toward the third trimester, she presented with marked elevations of 17α-hydroxyprogesterone and plasma renin activity. Careful management of endocrine and body fluid homeostasis allowed her to give birth to a healthy female infant with normal external genitalia. This case illustrates endocrinological parameters during pregnancy in a woman with classical salt-wasting CAH.

Upregulation of CDKN2A and suppression of cyclin D1 gene expressions in ACTH-secreting pituitary adenomas

OBJECTIVE

Cushing's disease (CD) is usually caused by ACTH-secreting pituitary microadenomas, while silent corticotroph adenomas (SCA) are macroadenomas without Cushingoid features. However, the molecular mechanism(s) underlying their different tumor growth remains unknown. The aim of the current study was to evaluate and compare the gene expression profile of cell cycle regulators and cell growth-related transcription factors in CD, SCA, and non-functioning adenomas (NFA).

DESIGN AND METHODS

Tumor tissue specimens resected from 43 pituitary tumors were studied: CD (n=10), SCA (n=11), and NFA (n=22). The absolute transcript numbers of the following genes were quantified with real-time quantitative PCR assays: CDKN2A (or p16(INK4a)), cyclin family (A1, B1, D1, and E1), E2F1, RB1, BUB1, BUBR1, ETS1, and ETS2. Protein expressions of p16 and cyclin D1 were semi-quantitatively evaluated by immunohistochemical study.

RESULTS AND CONCLUSION

CDKN2A gene expression was about fourfold greater in CD than in SCA and NFA. The gene expressions of cyclins D1, E1, and B1, but not of A1, in CD were significantly suppressed than those in NFA. Cyclin D1 gene expression positively correlated with cyclins B1 and E1. The gene expressions of E2F1, RB1, BUB1, BUBR1, ETS1, and ETS2 did not differ between each group. Positive immunostaining for p16 and negative immunostaining for cyclin D1 were more frequent in CD than in NFA; there were positive correlations between mRNA and protein expressions of p16 and cyclin D1. Thus, it is suggested that upregulated CDKN2A with the concomitant downregulated cyclin gene family is partly involved in the small size of ACTH-secreting adenoma.

Hepatocyte-protective and anti-oxidant effects of rifampicin on human chronic hepatitis C and murine acute hepatocyte disorder

Rifampicin (RFP) is a semisynthetic antibiotic derived from the rifamycins and is one of the most commonly used pharmaceutical compounds worldwide in the treatment of tuberculosis. We previously reported that low-dose and long-term oral administration of RFP to 6 hepatitis C virus-related liver cirrhosis patients who were at high risk for presenting with hepatocellular carcinoma (HCC) resulted in a marked suppression of the occurrence of HCC without showing an adverse effect. The underlying mechanism was found to be due to the anticancer effect based on the potent anti-angiogenic properties of RFP. The present study revealed that RFP has an additional hepatocyte-protective effect by lowering the release of hepatic enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in chronic hepatitis C patients. Experimentally, we were able to show that RFP had hepatocyte-protective effects in acute hepatocyte disorder models of mice and rats induced by concanavalin A and by D-galactosamine, respectively: RFP significantly prevented an increase in the levels of ALT, AST and lactate dehydrogenase in these animal models. In addition, we found that RFP had a strong anti-oxidant action which was approximately three times stronger than the action of silibinin, an anti-inflammatory agent of human hepatic stellate cells, implicating that the hepatocyte-protective effects of RFP are mediated by its anti-oxidant activity. These results reveal that oral administration of RFP exerts not only a prophylactic effect on the occurrence or recurrence of HCC for an extensive period of time, but also exerts hepatocyte-protective effects on both human chronic hepatitis C and acute hepatocyte disorder in rodent models, and the anti-oxidant activity of RFP is implicated to participate in the latter effects.

Inhibition of cancer progression by rifampicin: involvement of antiangiogenic and anti-tumor effects

Very recently, we reported that an antituberculous agent, rifampicin, exerts potent inhibitory effects on hepatic tumors when administered orally at low doses. The in vitro effects of rifampicin to rapidly downregulate angiogenesis and mitogenesis-related genes in cultured endothelial cells are reminiscent of endostatin, one of the most well-studied angiogenesis inhibitors. However, rifampicin at the expected hepatobiliary concentrations after low oral doses showed more complete antiproliferative effects on endothelial cells, which make rifampicin favorable as an adjunct anticancer regimen. Since rifampicin undergoes hepatic accumulation resulting from the enterohepatic circulation, it may be especially beneficial for targeting hepatobiliary tumors. In the present paper, we extend our observations on the antiangiogenic properties of rifampicin and further elaborate on its direct antitumor effects on a variety of human cancer-derived cells.

Release of salusin-beta from human monocytes/macrophages

Salusin-alpha and salusin-beta are related bioactive peptides biosynthesized from the same precursor, prosalusin. Despite the potent hemodynamic and proatherosclerotic activities of salusin-beta, its exact distribution and biological functions remain largely undetermined because of technical difficulties associated with its unique physicochemical characteristics, such as marked adhesiveness to polypropylene and polystyrene. By circumventing these problems, we recently established a specific radioimmunoassay for detecting immunoreactive human salusin-beta. In the current study, we demonstrated the release of salusin-beta from the human monoblastic leukemia cell lines, THP-1 and U937. Dilution curves of extracted conditioned media from both cells were parallel with those of standard human salusin-beta by radioimmunoassay. Reverse-phase high performance liquid chromatography coupled with radioimmunoassay detection of the culture supernatants revealed a major immunoreactive component that co-eluted with authentic salusin-beta. Both cell lines secreted salusin-beta-like immunoreactivity (LI) into serum-free media as a function of time (1234.3 + or - 122.7 and 186.7 + or - 9.1 fmol/10(5) cells per 24h). When THP-1 and U937 cells differentiated into macrophages after incubation with 2-O-tetradecanoylphorbol-13-acetate (TPA), they secreted far greater amounts of salusin-beta-LI into the culture supernatant (3351.9 + or - 899.3 and 1545.8 + or - 183.3 fmol/10(5) cells per 24h). TPA treatment accelerated the processing of prosalusin into its cleaved fragments, suggesting that the increased secretion of salusin-beta-LI in THP-1-derived macrophages was caused by the enhanced intracellular processing of prosalusin. Stimulation with the inflammatory cytokines, tumor necrosis factor alpha (TNF-alpha) and lipopolysaccharide (LPS), resulted in increased secretion of salusin-beta without inducing expression of the gene for preprosalusin, suggesting that TNF-alpha and LPS stimulated the release of salusin-beta. These data demonstrate that salusin-beta, which induces macrophage foam cell formation, is secreted in its authentic form from human monocytes/macrophages.

Expression of prosalusin in human neuroblastoma cells

Salusins, which are derived from the prosalusin precursor molecule, regulate hemodynamics, mitogenesis and atherogenesis. The preprosalusin gene is ubiquitously expressed, while the salusin-beta peptide is present in systemic endocrine cells and the neuroendocrine system. However, the regulatory mechanisms for the preprosalusin gene and prosalusin expression remain to be investigated. Real-time quantitative RT-PCR and salusin-alpha radioimmunoassay revealed that the neuroblastoma cell line, SK-N-SH, exhibited marked upregulation of preprosalusin mRNA and salusin-alpha-like immunoreactivity (LI) when incubated under 2% serum condition. However, SK-N-SH cells released a limited amount of salusin-alpha-LI into the culture supernatant. Reverse-phase high performance liquid chromatography coupled with radioimmunoassay after extraction of proteins from the conditioned media using an octyl-silica column did not reveal a component that co-eluted with authentic salusin-alpha. Western blotting of the nuclear extracts from SK-N-SH showed the expression of prosalusin and its cleaved fragments, but not authentic salusin-alpha. Addition of Jak-2 inhibitors to growing SK-N-SH cells cultured under 10% serum condition resulted in increased salusin-alpha-LI expression. Suppression of Jak-2 mRNA using siRNAs upregulated intracellular salusin-alpha-LI, as detected by immunofluorescence. In summary, the preprosalusin gene and prosalusin protein are expressed in a neuroblastoma cell line and upregulated by reduced serum. The Jak-2 pathway may be involved in the regulation of salusin expression.

Increased Urinary Kallikrein-Like Activity in the Syndrome of Inappropriate Secretion of Antidiuretic Hormone

The role of the kallikrein system in the natriuresis of SIADH was studied in 3 patients. Following free water intake, serum Na decreased. Urinary Na excretion, urinary aldosterone excretion and urinary kallikrein-like activity (UKaV) increased. Significant relationships were observed between UKaV and urinary aldosterone excretion during the study. Further, there were significant relationships between serum Na and UKaV, and between uric acid clearance and UKaV. In 1 patient, who was observed for a longer period, a significant relationship was observed between Na clearance and UKaV. We conclude that UKaV is increased during hyponatremia in SIADH by volume expansion. This increase in UKaV may play a role in the natriuresis in SIADH.

Biosynthesis and secretion of salusin-alpha from human cells

Salusins originally identified using bioinformatics analyses have been shown to act on the cardiovascular and endocrine systems. Although the hypotensive activity of salusin-alpha is limited, it exerts a significant anti-atherosclerotic effect via suppression of foam cell formation in human monocyte-derived macrophages by down-regulating acyl-CoA:cholesterol acyltransferase-1. Furthermore, serum salusin-alpha levels show a close negative correlation with the severity of atherosclerotic diseases. However, biosynthesis and secretion of salusin-alpha peptide from cultured mammalian cells have not been demonstrated to date. We examined the expression, synthesis and release of salusin-alpha in human-derived cell lines. Preprosalusin mRNA and protein were detected ubiquitously in all cells tested, whereas the processing of preprosalusin into salusin-alpha peptide is dependent upon each cell type. Immunohistochemical study revealed the most abundant salusin-alpha-like immunoreactivity to be present in HeLa cells which released salusin-alpha-like immunoreactivity into the culture supernatant. Analysis of extracted conditioned media from HeLa cells by reverse-phase high performance liquid chromatography coupled with radioimmunoassay detection revealed a single immunoreactive component that co-eluted with authentic salusin-alpha. These results present the first evidence that salusin-alpha is biosynthesized and released from human-derived cells.

Nitric oxide upregulates dimethylarginine dimethylaminohydrolase-2 via cyclic GMP induction in endothelial cells

Dimethylarginine dimethylaminohydrolase (DDAH) is an enzyme that metabolizes asymmetrical N(G),N(G)-dimethyl-L-arginine (ADMA) and N(G)-monomethyl-L-arginine (MMA), which are competitive endogenous inhibitors of NO synthase. However, it remains unknown whether NO itself influences DDAH activity and/or ADMA/MMA contents to regulate NO generation via a biofeedback mechanism. The present study was designed to examine the effects of NO on intracellular ADMA and MMA contents and DDAH gene expression levels and enzymatic activities in cultured rat aortic endothelial cells. The NO donors SNAP and NOR3 did not influence DDAH-1 expression but increased DDAH-2 mRNA and protein levels in concentration-dependent manners. SNAP upregulated DDAH enzymatic activity and reduced the MMA and ADMA contents but did not affect the symmetrical N(G),N'(G)-dimethyl-L-arginine and L-arginine levels, thereby negating a mediatory role for system y(+) in ADMA/MMA downregulation. The cGMP agonists 8-bromo-cGMP and C-type natriuretic peptide also stimulated DDAH-2 gene and protein expression levels and DDAH activity and increased the amount of nitrite/nitrate released into the culture supernatants. SNAP-induced DDAH-2 gene expression and DDAH activity were significantly inhibited by a protein kinase G inhibitor, KT5823, and a soluble guanylate cyclase inhibitor, ODQ, suggesting a mediatory role for cGMP in NO-induced DDAH-2 expression. Suppression of DDAH-2 mRNA using small interfering RNA technology abrogated NO-induced DDAH-2 expression. These data demonstrate that NO acts on endothelial cells to induce DDAH-2 expression via a cGMP-mediated process to reduce ADMA/MMA. Thus, the DDAH-2-ADMA/MMA-endothelial NO synthase regulatory pathway and NO-induced cGMP constitute a positive feedback loop that ultimately serves to maintain NO levels in the endothelial environment.

Serum salusin-alpha levels are decreased and correlated negatively with carotid atherosclerosis in essential hypertensive patients

Salusin-alpha is a new bioactive peptide with mild hypotensive and bradycardic effects. Our recent study showed that salusin-alpha suppresses foam cell formation in human monocyte-derived macrophages by down-regulating acyl-CoA:cholesterol acyltransferase-1, contributing to its anti-atherosclerotic effect. To clarify the clinical implications of salusin-alpha in hypertension and its complications, we examined the relationship between serum salusin-alpha levels and carotid atherosclerosis in hypertensive patients. The intima-media thickness (IMT) and plaque score in the carotid artery, blood pressure, serum levels of salusin-alpha, and atherosclerotic parameters were determined in 70 patients with essential hypertension and in 20 normotensive controls. There were no significant differences in age, gender, body mass index, fasting plasma glucose level, or serum levels of high-sensitive C-reactive protein, high- or low-density lipoprotein (LDL) cholesterol, small dense LDL, triglycerides, lipoprotein(a), or insulin between the two groups. Serum salusin-alpha levels were significantly lower in hypertensive patients than in normotensive controls. The plasma urotensin-II level, maximal IMT, plaque score, systolic and diastolic blood pressure, and homeostasis model assessment for insulin resistance (HOMA-IR) were significantly greater in hypertensive patients than in normotensive controls. In all subjects, maximal IMT was significantly correlated with age, systolic blood pressure, LDL cholesterol, urotensin-II, salusin-alpha, and HOMA-IR. Forward stepwise multiple linear regression analysis revealed that salusin-alpha levels had a significantly independent and negative association with maximal IMT. Serum salusin-alpha levels were significantly lower in accordance with the severity of plaque score. Our results suggest that the decrease in serum salusin-alpha, an anti-atherogenic peptide, may be associated with carotid atherosclerosis in hypertensive patients.

Differential gene expression in ACTH -secreting and non-functioning pituitary tumors

OBJECTIVE

Differential expression of several genes between ACTH-secreting pituitary tumors causing Cushing' disease (CD), silent corticotroph adenoma (SCA), and non-functioning pituitary tumors (NFT) was investigated.

DESIGN AND METHODS

We used tissue specimens from 35 pituitary tumors (12 CD, 8 SCA, and 15 NFT). Steady-state mRNA levels of the genes related to proopiomelanocortin (POMC) transcription, synthesis, processing, and secretion, such as neurogenic differentiation 1 (NeuroD1), T-box 19 (Tpit), corticotropin releasing hormone receptor (CRHR), vasopressin receptor 1b (V1bR), prohormone convertase (PC) 1/3 and PC2, 11beta-hydroxysteroid dehydrogenase (11beta-HSD) type 1 and type 2, glucocorticoid receptor alpha (GRalpha), annexin A1, histone deacetylase 2 (HDAC2), and BRM/SWI2-related gene 1, were determined by real-time RT-PCR.

RESULTS AND CONCLUSION

POMC and Tpit mRNA levels were greater in CD and SCA than those in NFT. NeuroD1 mRNA levels were less in CD than those in NFT, but almost comparable between SCA and NFT. PC1/3 mRNA levels were greater in CD, but less in SCA than those in NFT. PC2 mRNA levels in CD and SCA were less than those in NFT. CRHR, V1bR, and 11beta-HSD2 mRNA levels in CD were greater than those in SCA and NFT. HDAC2 mRNA levels in CD and SCA were lower than those in NFT. In conclusion, our study demonstrated that the genes related to transcription, synthesis, processing, and secretion of POMC are differentially regulated in ACTH-secreting pituitary tumors causing CD and SCA compared with those in NFT. This may partly explain the development of clinically active and inactive CD.

Chronic blockade of nitric oxide synthesis reduces adiposity and improves insulin resistance in high fat-induced obese mice

Genetic deletion of inducible nitric oxide synthase (NOS) in mice has been shown to improve high-fat diet (HFD)-induced insulin resistance. However, a pathophysiological role of endogenous nitric oxide (NO) in obesity-related insulin resistance remains controversial. To address this issue, we examined the metabolic phenotypes in HFD-induced obese mice with chronic blockade of NO synthesis by a NOS inhibitor, N(G)-nitro-l-arginine methyl ester (L-NAME). Six-week-old male C57BL/6j mice were provided free access to either a standard diet (SD) or a HFD and tap water with or without L-NAME (100 mg/kg.d) for 12 wk. L-NAME treatment significantly attenuated body weight gain of mice fed either SD or HFD without affecting calorie intake. L-NAME treatment in HFD-fed mice improved glucose tolerance and insulin sensitivity. HFD feeding induced inducible NOS mRNA expression, but not the other two NOS isoforms, in white adipose tissue (WAT) and skeletal muscle. L-NAME treatment up-regulated uncoupling protein-1 in brown adipose tissue of HFD-fed mice but down-regulated monocyte chemoattractant protein-1 and CD68 mRNAs levels in WAT. HFD feeding up-regulated leptin mRNA levels but conversely down-regulated adiponectin mRNA levels in WAT, but these effects were unaffected by L-NAME treatment. Moreover, L-NAME treatment also increased peroxisome proliferator-uncoupling protein-3 mRNA levels in skeletal muscles of HFD-fed mice. Increased urinary excretion of norepinephrine after HFD feeding was augmented in L-NAME-treated mice. Insulin-stimulated tyrosine phosphorylation of insulin receptor substrate-1 and serine phosphorylation of Akt/Akt2 in soleus muscle was markedly impaired in HFD-fed mice but reversed by L-NAME treatment. In conclusion, chronic NOS blockade by L-NAME in mice ameliorates HFD-induced adiposity and glucose intolerance, accompanied by reduced adipose inflammation and improved insulin signaling in skeletal muscle, suggesting that endogenous NO plays a modulatory role in the development of obesity-related insulin resistance.

Angiotensin II receptor type 1-mediated vascular oxidative stress and proinflammatory gene expression in aldosterone-induced hypertension: the possible role of local renin-angiotensin system

Recently, aldosterone has been shown to activate local renin-angiotensin system in vitro. To elucidate the potential role of local renin-angiotensin system in aldosterone-induced cardiovascular injury, we investigated the effects of selective mineralocorticoid receptor (MR) antagonist eplerenone (EPL), angiotensin (Ang) II type 1 receptor antagonist candesartan (ARB), and superoxide dismutase mimetic tempol (TEM) on the development of hypertension, vascular injury, oxidative stress, and inflammatory-related gene expression in aldosterone-treated hypertensive rats. The increased systolic blood pressure and vascular inflammatory changes were attenuated by cotreatment either with EPL, ARB, or TEM. Aldosterone increased angiotensin-converting enzyme expression in the aortic tissue; its effects were blocked by EPL but not by ARB or TEM. Aldosterone also increased Ang II contents in the aortic tissue in the presence of low circulating Ang II concentrations. Aldosterone induced expression of various inflammatory-related genes, whose effects were abolished by EPL, whereas the inhibitory effects of ARB and TEM varied depending on the gene. Aldosterone caused greater accumulation of the oxidant stress marker 4-hydroxy-2-neonenal in the endothelium; its effect was abolished by EPL, ARB, or TEM. Aldosterone increased mRNA levels of reduced nicotinamide adenine dinucleotide phosphate oxidase components; their effect was abolished by EPL, whereas ARB and TEM decreased only the p47phox mRNA level but not that of p22phox or gp91phox. The present findings suggest that the Ang II-dependent pathway resulting from vascular angiotensin-converting enzyme up-regulation and Ang II-independent pathway are both involved in the underlying mechanisms resulting in the development of hypertension, vascular inflammation, and oxidative stress induced by aldosterone.

Presence of immunoreactive salusin-alpha in human serum and urine

Salusins, identified from a full-length enriched human cDNA library by bioinformatics analyses, show mitogenic, neuromodulatory and hemodynamic activities in rats. They are expressed in a wide variety of human tissues, but their precise structures and levels in human body fluids remain unknown. We developed a radioimmunoassay suitable for the detection of immunoreactive human salusin-alpha and characterized the molecular forms and concentrations of salusin-alpha in human serum and urine. The assay allowed for measurement of immunoreactive salusin-alpha concentrations as low as 1 fmol/tube after extraction of serum with an octyl-silica column, and the concentration required for 50% inhibition of binding was 40 fmol/tube. Cross-reactivities with salusin-beta and other bioactive peptides were negligible. Salusin-alpha-like immunoreactivity in normal human serum and urine ranged from 11.0 to 40.4 pmol/l (mean+/-S.D., 23.3+/-8.1 pmol/l, n=31) and from 18.6 to 367.3 pmol/l (mean+/-S.D., 156.8+/-95.8 pmol/l), respectively. Reverse-phase high performance liquid chromatography coupled with radioimmunoassay detection revealed a major immunoreactive component that coeluted with authentic salusin-alpha. These data indicate the presence of salusin-alpha in human serum and urine, thereby verifying the initially predicted processing sites for salusin-alpha in humans.

Salusin β is a surrogate ligand of the mas-like G protein-coupled receptor MrgA1

The mas-like G protein-coupled receptors form a subfamily of G protein-coupled receptors that includes variable member numbers across different species and that have been shown to bind a wide variety of ligands from peptides to amino acid derivatives. While screening a library of peptides against different orphan G protein-coupled receptors, we found that human salusin beta activates the mouse mas-like G protein-coupled receptor, mMrgA1 with an EC(50) of about 300 nM. Salusin beta is a bioactive peptide recently discovered through bioinformatics analysis which stimulates arginine-vasopressin release from rat pituitary and causes rapid and profound hypotension and bradycardia. However, when we further analyzed the generality of the mMrgA1 activation, we found that human salusin beta does not activate corresponding human mas-like G protein-coupled receptors. Our results show that human salusin beta is a surrogate ligand of the mouse MrgA1 and raises a cautionary flag for experiments that analyze the pharmacological profiles of mas-like G protein-coupled receptors from different species.

Coexistence of salusin and vasopressin in the rat hypothalamo-hypophyseal system

Salusins are two newly discovered TOR-related peptides consisting of 28 and 20 amino acids and designated salusin-alpha and salusin-beta, respectively. Using immunohistochemistry techniques, salusin-like immunoreactivity was detected in the rat hypothalamo-neurohypophyseal tract and immunopositive cells were distributed in the suprachiasmatic, supraoptic and paraventricular nucleus. In the paraventricular nucleus, salusin-like immunoreactivity was observed both in parvocellular and magnocellular neurons. Many salusin-positive nerve fibers and their terminals were identified in the internal layer of the median eminence and posterior pituitary. Less intense salusin-positive staining of fibers and terminals was found in the suprachiasmatic nucleus and external layer of the median eminence. Dual immunostaining was performed to determine if salusin coexisted with vasopressin or oxytocin in the hypothalamus. Most of the salusin-like immunoreactivity was detected in vasopressin- but not in oxytocin-containing neurons in these nuclei. The functional significance of the coexistence of salusin with vasopressin is discussed, including the possibility that salusin participates in the regulation of blood pressure.