Neurotensin

Advances and challenges in organ-on-chip technology: toward mimicking human physiology and disease in vitro

Organs-on-chips have been tissues or three-dimensional (3D) mini-organs that comprise numerous cell types and have been produced on microfluidic chips to imitate the complicated structures and interactions of diverse cell types and organs under controlled circumstances. Several morphological and physiological distinctions exist between traditional 2D cultures, animal models, and the growing popular 3D cultures. On the other hand, animal models might not accurately simulate human toxicity because of physiological variations and interspecies metabolic capability. The on-chip technique allows for observing and understanding the process and alterations occurring in metastases. The present study aimed to briefly overview single and multi-organ-on-chip techniques. The current study addresses each platform's essential benefits and characteristics and highlights recent developments in developing and utilizing technologies for single and multi-organs-on-chips. The study also discusses the drawbacks and constraints associated with these models, which include the requirement for standardized procedures and the difficulties of adding immune cells and other intricate biological elements. Finally, a comprehensive review demonstrated that the organs-on-chips approach has a potential way of investigating organ function and disease. The advancements in single and multi-organ-on-chip structures can potentially increase drug discovery and minimize dependency on animal models, resulting in improved therapies for human diseases.

The Neurotensinergic System: A Target for Cancer Treatment

BACKGROUND

The scientific interest regarding the involvement of peptides in cancer has increased in the last years. In tumor cells the overexpression of peptides and their receptors is known and new therapeutic targets for the treatment of cancer have been suggested. The overexpression of the neurotensinergic system has been associated with poor prognosis, tumor size, higher tumor aggressiveness, increased relapse risk and worse sensitivity to chemotherapy agents.

OBJECTIVE

The aim of this review is to update the findings regarding the involvement of the neurotensinergic system in cancer to suggest anticancer therapeutic strategies targeting this system. The neurotensin (NT) precursor, NT and its receptors (NTR) and the involvement of the neurotensinergic system in lung, breast, prostate, gastric, colon, liver and pancreatic cancers, glioblastoma, neuroendocrine tumors and B-cell leukemia will be mentioned and discussed as well as the signaling pathways mediated by NT. Some research lines to be developed in the future will be suggested such as: molecules regulating the expression of the NT precursor, influence of the diet in the development of tumors, molecules and signaling pathways activated by NT and antitumor therapeutic strategies targeting the neurotensinergic system.

CONCLUSION

NT, via the NTR, exerts oncogenic (tumor cell proliferation, invasion, migration, angiogenesis) and antiapoptotic effects, whereas NTR antagonists inhibit these effects. NTR expression can be used as a diagnostic tool/therapeutic target and the administration of NTR antagonists as antitumor drugs could be a therapeutic strategy to treat tumors overexpressing NTR.

The mRNA and lncRNA landscape of the non-pregnant endometrium during the oestrus cycle in dairy goat

Cyclic changes in the endometrium are essential for embryo implantation in mammals; many studies report that such changes constitute a complex process involving numerous molecular mediators. In the present study, goat endometria at oestrus Day 5 and oestrus Day 15 were selected to systematically analyse the transcriptome using strand-specific Ribo-Zero RNA sequencing. Over 120 million high-quality paired-end reads were generated and 440400 transcripts were identified in the endometrial tissue of dairy goats. In total, 489 differentially expressed mRNAs and 854 differentially expressed long non-coding RNAs were identified when comparing the endometrium at goat endometria at oestrus Day 5 and oestrus Day 15. Neurotensin was found to play a potentially important role in the non-pregnant goat endometrium during the oestrus cycle. Furthermore, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes analyses of the cis-target genes of the differentially expressed long non-coding RNAs showed that GO:0005198 (structural molecule activity) and ko04510 (focal adhesion) might be involved in cyclic endometrial changes. Taken together, the resulting transcriptomic profiles elucidate global trends in mRNA and lncRNA expression in non-pregnant endometria during the oestrus cycle in dairy goats.

Expression of neurotensin receptor 1 in endometrial adenocarcinoma is correlated with histological grade and clinical outcome

The promalignant effects of neurotensin (NTS) are sustained in many solid tumors, including hormone-dependent cancers. As the endometrium is also subjected to hormonal regulation, we evaluated the contribution of NTS to endometrial carcinogenesis. Neurotensin receptor 1 (NTSR1) expression and NTSR1 promoter methylation (HM450) were analyzed in 385 cases of endometrial carcinoma from The Cancer Genome Atlas (TCGA). Additionally, from a series of 100 endometrial carcinomas, and 66 benign endometrium samples, NTS and NTSR1 labeling was evaluated by immunohistochemistry. Using TCGA series, NTSR1 messenger RNA (mRNA) level was negatively correlated with overall survival (OS) and progression-free survival (PFS) (p = 0.0012 and p = 0.0116, respectively), and positively correlated with the grade (p = 0.0008). When including only endometrioid carcinomas, NTSR1 mRNA level continued to be negatively correlated with OS (log-rank: p < 0.0001) and PFS (log-rank: p = 0.002). A higher NTSR1 mRNA level was significantly associated with a loss of NTSR1 promoter methylation. Immunohistochemical expression of NTS and NTSR1 was significantly increased in adenocarcinoma (n = 100), as compared to benign endometrium (p < 0.001). NTSR1 expression was positively correlated with grade (p = 0.004). High immunohistochemical expression of cytoplasmic NTSR1 was significantly correlated with a shorter OS and PFS (p < 0.001 and p = 0.001, respectively). This correlation remained significant when excluding non-endometrioid subtypes (p = 0.04 and p = 0.02, respectively). In multivariate analysis, the expression of NTSR1 was an independent prognostic factor (p = 0.004). NTSR1 overexpression is a poor prognostic factor in endometrial cancer, highlighting the contribution of NTS in endometrial cancer progression and its uses as a prognostic marker, and as a potential therapeutic target.

NT Agonist Regulates Expression of Nuclear High-affinity Neurotensin Receptors

Neurotensin (NT) exerts multiple functions in the central nervous system and peripheral tissues. Its actions are mainly mediated by a high-affinity G-protein-coupled receptor, the NT-1 receptor. In this study we demonstrated a nuclear NT binding site in different cellular models. We first noted that a large percentage of NT-1 receptor cell body immunoreactivity was located in the nuclear soma and nuclear envelope of rat substantia nigra, a brain area rich in NT-containing axon terminals. The NT-1 receptor was also visualized in purified nuclei from CHO cells stably transfected with NT-1 receptor coupled to the enhanced green fluorescence protein by immunocytochemistry. We observed that both the nuclear envelope and the nuclear soma were labeled, and the labeling intensity significantly increased after NT agonist treatment. These results suggested that NT-1 receptors, present in both the nuclear soma and the nuclear envelope, can be modulated by the ligand. Lastly, [125I]-NT binding experiments performed on isolated nuclei from a human lung cancer cell line endogenously expressing NT-1 receptor and NT, LNM35, revealed the existence of nuclear Gpp(NHp)-sensitive binding sites. These binding sites markedly decreased when cells were chronically treated with an NT-1 receptor antagonist, SR 48692. Taken together, these data suggest that the agonist regulates the expression of nuclear NT-1 receptors.

Organ-on-a-Chip: New Platform for Biological Analysis

Direct detection and analysis of biomolecules and cells in physiological microenvironment is urgently needed for fast evaluation of biology and pharmacy. The past several years have witnessed remarkable development opportunities in vitro organs and tissues models with multiple functions based on microfluidic devices, termed as “organ-on-a-chip”. Briefly speaking, it is a promising technology in rebuilding physiological functions of tissues and organs, featuring mammalian cell co-culture and artificial microenvironment created by microchannel networks. In this review, we summarized the advances in studies of heart-, vessel-, liver-, neuron-, kidney- and Multi-organs-on-a-chip, and discussed some noteworthy potential on-chip detection schemes.

Cardiovascular biomarkers and sex: the case for women

Measurement of biomarkers is a critical component of cardiovascular care. Women and men differ in their cardiac physiology and manifestations of cardiovascular disease. Although most cardiovascular biomarkers are used by clinicians without taking sex into account, sex-specific differences in biomarkers clearly exist. Baseline concentrations of many biomarkers (including cardiac troponin, natriuretic peptides, galectin-3, and soluble ST2) differ in men versus women, but these sex-specific differences do not generally translate into a need for differential sex-based cut-off points. Furthermore, most biomarkers are similarly diagnostic and prognostic, regardless of sex. Two potential exceptions are cardiac troponins measured by high-sensitivity assay, and proneurotensin. Troponin levels are lower in women than in men and, with the use of high-sensitivity assays, sex-specific cut-off points might improve the diagnosis of myocardial infarction. Proneurotensin is a novel biomarker that was found to be predictive of incident cardiovascular disease in women, but not men, and was also predictive of incident breast cancer. If confirmed, proneurotensin might be a unique biomarker of disease risk in women. With any biomarker, an understanding of sex-specific differences might improve its use and might also lead to an enhanced understanding of the physiological differences between the hearts of men and women.

The actions of neurotensin in rat bladder detrusor contractility

This study assessed the expression, distribution and function of neurotensin (NTs) and two main neurotensin receptors (NTSR), NTSR1 and NTSR2 in normal rat urinary bladders. NTs is primarily located in the suburothelium and the interstitium of smooth muscle bundles. The NTSR1 and NTSR2 receptor subtypes are found to co-localize with smooth muscle cells (SMCs). NTs not only can directly act on bladder SMCs to induce intracellular calcium mobilization by activating the phospholipase C/inositol triphosphate (PLC/IP3) pathway, promoting extracellular calcium influx through a non-selective cation channels, but may be also involved in the modulation of the cholinergic system. Nowadays, the selective antimuscarinic drugs (solifenacin) and the selective beta 3-adrenergic agonist (mirabegron) are used as the first-line pharmacotherapy for overactive bladder (OAB), but without satisfactory treatment benefits in some patients. This study provided evidence suggesting that bladder NTs may play an important role in the regulation of micturition. Further research is needed to investigate the effects of NTs on bladder contractility and the underlying mechanism, which might reveal that the administration of NTSR antagonists can potentially relieve the symptoms of OAB by coordination with antimuscarinic pharmacotherapy.

The potential of neurotensin secreted from neuroendocrine tumor cells to promote gelsolin-mediated invasiveness of prostate adenocarcinoma cells

Neuroendocrine (NE) cells in prostate cancer have been shown to be associated with the progression of prostate cancer. However, little is known about the molecular basis of this association. We have previously demonstrated that NE cells promote metastasis of a human prostate cancer cell line (LNCaP) with overexpression of the gelsolin gene. The purpose of this study was to investigate the interactions between NE cells and LNCaP cells and the involvement of gelsolin in contributing to the invasive potential of LNCaP cells. In addition, we examined whether neurotensin induced gelsolin-mediated invasion. We used the NE cell line NE-CS that was established from the prostate of the LPB-Tag 12T-10 transgenic mouse. Small interfering RNA (siRNA) targeting gelsolin or not targeting it was transfected into LNCaP cells. Cell invasion was assessed by Matrigel invasion assay. The supernatant of NE-CS cells and neurotensin induced the transformation of LNCaP cells. Neurotensin was observed in the supernatant of NE-CS cells but not in LNCaP cells. The siRNA targeting of gelsolin resulted in inhibition of invasion of LNCaP cells in the culture medium with neurotensin added, and in the supernatant of NE-CS cells with epidermal growth factor. The invasive potential of LNCaP cells enhanced by neurotensin or the supernatant of NE-CS cells through neurotensin receptor 1 (NTSR1) was blocked by a phospholipase Cγ inhibitor and an intracellular calcium chelator, with concomitant gelsolin suppression. This study indicates that NE cells and neurotensin induce gelsolin-mediated invasion of LNCaP cells through NTSR1 activation.

Brain neurotensin, psychostimulants, and stress--emphasis on neuroanatomical substrates

Neurotensin (NT) is a peptide that is widely distributed throughout the brain. NT is involved in locomotion, reward, stress and pain modulation, and in the pathophysiology of drug addiction and depression. In its first part this review brings together relevant literature about the neuroanatomy of NT and its receptors. The second part focuses on functional-anatomical interactions between NT, the mesotelencephalic dopamine system and structures targeted by dopaminergic projections. Finally, recent data about the actions of NT in processes underlying behavioral sensitization to psychostimulant drugs and the involvement of NT in the regulation of the hypothalamo-pituitary-adrenal gland axis are considered.

Neuroendocrine Regulation of Frog Adrenocortical Cells by Neurotensin

We previously characterized the primary structure of neurotensin (NT) from an extract of the intestine of the frog Rana esculenta. In this study, we provide evidence for the involvement of NT in the neurocrine regulation of the secretory activity of frog adrenocortical cells. Immunohistochemical studies revealed that the adrenal gland of R. esculenta is innervated by a dense network of NT-immunoreactive fibers. Graded concentrations of frog NT induced a dose-dependent stimulation of corticosterone and aldosterone secretion by frog adrenocortical explants through activation of two receptors with pEC(50) of 9.8 and 6.9. These data support the view that NT, released by nerve fibers within the frog adrenal gland, acts locally to control corticosteroid secretion.

Involvement of MAP-kinase, PI3-kinase and EGF-receptor in the stimulatory effect of Neurotensin on DNA synthesis in PC3 cells

The mechanism by which neurotensin (NT) promotes the growth of prostate cancer epithelial cells is not yet defined. Here, androgen-independent PC3 cells, which express high levels of the type 1 NT-receptor (NTR1), are used to examine the involvement of epidermal growth factor receptor (EGFR), mitogen-activated protein kinases (ERK, SAPK/JNK and p38), PI3 kinase and PKC in the mitogenic effect of NT. NT dose dependently (0.1-30 nM) enhanced phosphorylation of EGFR, ERK and Akt, reaching maximal levels within 3 min as measured by Western blotting. These effects were associated with an accumulation of EGF-like substance(s) in the medium (assayed by EGFR binding) and a 2-fold increase in DNA synthesis (assayed by [3H]thymidine incorporation). The DNA synthesis enhancement by NT was non-additive with that of EGF. The NT-induced stimulation of EGFR/ERK/Akt phosphorylation and DNA synthesis was inhibited by EGFR-tyrosine kinase inhibitors (AG1478, PD153035), metallo-endopeptidase inhibitor phosphoramidon and by heparin, but not by neutralizing anti-EGF antibody. Thus, transactivation of EGFR by NT involved heparin-binding EGF (HB-EGF or amphiregulin) rather than EGF. The effects of NT on EGFR/ERK/Akt activation and DNA synthesis were attenuated by PLC-inhibitor (U73122), PKC-inhibitors (bisindolylmaleimide, staurosporine, rottlerin), MEK inhibitor (U0126) and PI3 kinase inhibitors (wortmannin, LY 294002). We conclude that NT stimulated mitogenesis in PC3 cells by a PKC-dependent ligand-mediated transactivation of EGFR, which led to stimulation of the Raf-MEK-ERK pathway in a PI3 kinase-dependent manner.

Involvement of mast cells in basal and neurotensin-induced intestinal absorption of taurocholate in rats

Neurotensin (NT), a hormone released from intestine by ingested fat, facilitates lipid digestion by stimulating pancreatic secretion and slowing the movement of chyme. In addition, NT can contract the gall bladder and enhance the enterohepatic circulation (EHC) of bile acids to promote micelle formation. Our recent finding that NT enhanced and an NT antagonist inhibited [(3)H]taurocholate ([(3)H]TC) absorption from proximal rat small intestine indicated a role for endogenous NT in the regulation of EHC. Here, we postulate the involvement of intestinal mast cells in the TC uptake process and in the stimulatory effect of NT. In anesthetized rats with the bile duct cannulated for bile collection, infusion of NT (10 pmol.kg(-1).min(-1)) enhanced the [(3)H]TC recovery rate from duodenojejunum by 2.2-fold. This response was abolished by pretreatment with mast cell stabilizers (cromoglycate, doxantrazole) and inhibitors of mast cell mediators (diphenhydramine, metergoline, zileuton). In contrast, mast cell degranulators (compound 48/80, substance P) and mast cell mediators (histamine, leukotriene C(4)) reproduced the effect of NT. N(G)-nitro-l-arginine methyl ester enhanced and l-arginine inhibited basal and NT-induced TC uptake, consistent with the known inhibitory effect of nitric oxide (NO) on mast cell reactivity. These results argue that basal and NT-stimulated TC uptake in rat jejunum are similarly dependent on mast cells, are largely mediated by release of mast cell mediators, and are subject to regulation by NO.

Metalloproteinase-dependent transforming growth factor-alpha release mediates neurotensin-stimulated MAP kinase activation in human colonic epithelial cells

Expression of the neuropeptide neurotensin (NT) and its high affinity receptor (NTR1) is increased during the course of Clostridium difficile toxin A-induced acute colitis, and NTR1 antagonism attenuates the severity of toxin A-induced inflammation. We recently demonstrated in non-transformed human colonic epithelial NCM460 cells that NT treatment caused activation of a Ras-mediated MAP kinase pathway that significantly contributes to NT-induced interleukin-8 (IL-8) secretion. Here we used NCM460 cells, which normally express low levels of NTR1, and NCM460 cells stably transfected with NTR1 to identify the upstream signaling molecules involved in NT-NTR1-mediated MAP kinase activation. We found that inhibition of the epidermal growth factor receptor (EGFR) by either an EGFR neutralizing antibody or by its specific inhibitor AG1478 (0.2 microm) blocked NT-induced MAP kinase activation. Moreover, NT stimulated tyrosine phosphorylation of the EGFR, and pretreatment with a broad spectrum metalloproteinase inhibitor batimastat reduced NT-induced MAP kinase activation. Using neutralizing antibodies against the EGFR ligands EGF, heparin-binding-EGF, transforming growth factor-alpha (TGFalpha), or amphiregulin we have shown that only the anti-TGFalpha antibody significantly decreases NT-induced phosphorylation of EGFR and MAP kinases. Furthermore, inhibition of the EGF receptor by AG1478 significantly reduced NT-induced IL-8 promoter activity and IL-8 secretion. This is the first report demonstrating that NT binding to NTR1 transactivates the EGFR and that this response is linked to NT-mediated proinflammatory signaling. Our findings indicate that matrix metalloproteinase-mediated release of TGFalpha and subsequent EGFR transactivation triggers a NT-mediated MAP kinase pathway that leads to IL-8 gene expression in human colonic epithelial cells.

Site-specific DNA methylation contributes to neurotensin/neuromedin N expression in colon cancers

The neurotensin/neuromedin N (NT/N) gene is expressed in fetal colon, repressed in newborn and adult colon, and reexpressed in approximately 25% of colon cancers. Our purpose was to determine the effect of gene methylation on NT/N silencing in colon cancers. We found that the NT/N gene was expressed in human colon cancer cell line KM12C but not in KM20 colon cancer cells. Bisulfite genomic sequencing demonstrated that all CpG dinucleotides in the region from -373 to +100 of the NT/N promoter, including a CpG site in a distal consensus AP-1 site, were methylated in KM20 but unmethylated in KM12C cells. Treatment of KM20 cells with demethylating agent 5-azacytidine induced NT/N expression, suggesting a role for DNA methylation in silencing of NT/N in colon cancers. To better elucidate the mechanisms responsible for NT/N repression by DNA methylation, we performed gel shift assays using an oligonucleotide probe corresponding to the distal AP-1 consensus sequence of the NT/N promoter. Methylation of the oligonucleotide probe inhibited protein binding to the distal AP-1 site of the NT/N promoter, suggesting a potential mechanism of NT/N gene repression in colon cancers. We show that DNA methylation plays a role in NT/N gene silencing in the human colon cancer KM20 and that NT/N expression in KM12C cells is associated with demethylation of the CpG sites. DNA methylation likely contributes to NT/N gene expression noted in human colon cancers.

Sequences required for induction of neurotensin receptor gene expression during neuronal differentiation of N1E-115 neuroblastoma cells

The promoter region of the mouse high affinity neurotensin receptor (Ntr-1) gene was characterized, and sequences required for expression in neuroblastoma cell lines that express high affinity NT-binding sites were characterized. Me(2)SO-induced neuronal differentiation of N1E-115 neuroblastoma cells increased both the expression of the endogenous Ntr-1 gene and reporter genes driven by NTR-1 promoter sequences by 3-4-fold. Deletion analysis revealed that an 83-base pair promoter region containing the transcriptional start site is required for Me(2)SO activation. Detailed mutational analysis of this region revealed that a CACCC box and the central region of a large GC-rich palindrome are the crucial cis-regulatory elements required for Me(2)SO induction. The CACCC box is bound by at least one factor that is induced upon Me(2)SO treatment of N1E-115 cells. The Me(2)SO effect was found to be both selective and cell type-restricted. Basal expression in the neuroblastoma cell lines required a distinct set of sequences, including an Sp1-like sequence, and a sequence resembling an NGFI-A-binding site; however, a more distal 5' sequence was found to repress basal activity in N1E-115 cells. These results provide evidence that Ntr-1 gene regulation involves both positive and negative regulatory elements located in the 5'-flanking region and that Ntr-1 gene activation involves the coordinate activation or induction of several factors, including a CACCC box binding complex.

Synergistic effects of neurotensin and beta-adrenergic agonist on 3,5-cyclic adenosine monophosphate accumulation and DNA synthesis in prostate cancer PC3 cells

Since neurotensin is often co-stored with catecholamines and since it can excite the release of dopamine and norepinephrine, responses to this peptide might depend upon the activity of catecholaminergic systems. In this study, we used prostate cancer PC3 cells, which express neurotensin receptors and 12-adrenergic receptors, to demonstrate that neurotensin can potentiate the effects of isoproterenol on 3',5'-cyclic adenosine monophosphate (cAMP) formation and on inhibition of DNA synthesis. While neurotensin had only a slight effect on basal cAMP levels, it nearly doubled the response to isoproterenol even at maximal levels without altering potency. Neurotensin increased the rate of cAMP accumulation and the steady-state level achieved. Consistent with the known antimitogenic action of dibutyryl-cAMP in PC3 cells, isoproterenol was found to inhibit DNA synthesis concentration-dependently, measured using [3H]thymidine. Neurotensin enhanced DNA synthesis when given alone. However, it inhibited DNA synthesis when given with a threshold level of isoproterenol, which by itself had no significant effect. These results, demonstrating cross-talk in the neurotensin and beta-adrenergic signaling pathways, suggest that there may be other physiologic instances of similar interactions between neurotensin and catecholamines.

Neurotensin enhances agonist-induced cAMP accumulation in PC3 cells via Ca2+ -dependent adenylyl cyclase(s)

A human prostate cancer cell line (PC3) with abundant neurotensin (NT) receptors was used to demonstrate that NT potentiated 3',5'-cyclic adenosine monophate (cAMP) accumulation in response to a variety of stimuli, including both direct forskolin (F) and indirect (prostaglandin, (PGE2), isoproterenol (ISO) and cholera toxin (CTx)) activators of adenylyl cyclase. Several mechanisms were investigated and our results indicated an effect on the rate of cAMP formation and not on degradation or extrusion. For each stimulus, NT enhanced efficacy without altering EC50. The effect of NT did not involve stimulatory G-protein (Gs)-activation or interference with a tonic inhibitory G-protein (Gi)-mediated inhibition. A similar response was obtained when NT was added with the stimulus or given as a two minute pulse which was removed prior to addition of stimulus. The potentiating activity disappeared with a t1,2 of approximately 15 min. NT transiently elevated cellular [Ca2+]i and its effects on cAMP could be mimicked by [Ca2+]i-elevating agents (uridine triphosphate (UTP), thapsigargin and ionomycin). Buffering cellular [Ca2+]i with 1,2-bis (2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA-AM) inhibited cAMP responses to ISO and F in presence and absence of NT. These data support the idea that NT potentiated cAMP formation in response to a variety of stimuli by facilitating the activation of Ca2+ -dependent adenylyl cyclases.

DNA methylation contributes to expression of the human neurotensin/neuromedin N gene

The gut and liver share a common embryological origin. The gene encoding the gut hormone neurotensin/neuromedin N (NT/N) is expressed in the adult small bowel, and NT/N is transiently expressed in the fetal liver, suppressed in the adult liver, and reexpressed in certain liver cancers. In our present study, we found that the NT/N gene was expressed at high levels in the human hepatoma cell line Hep 3B but was not expressed in Hep G2 cells. To further determine the mechanisms regulating NT/N expression, we performed Southern blotting and gene cloning techniques. Neither alteration nor mutation of the NT/N gene was responsible for this differential NT/N expression pattern. Human NT/N promoter constructs were transfected into either Hep 3B or Hep G2. Both cell lines supported NT/N transcription, indicating that the absence of NT/N expression in Hep G2 cells was due to mechanisms other than the absence of positive transcription factors. The role of DNA methylation was next assessed. Methylation of NT/N promoter constructs in vitro resulted in a 67-fold reduction in promoter activity, whereas treatment with the demethylating agent 5-azacytidine induced NT/N expression in Hep G2 cells, thus suggesting that DNA methylation plays a role in the expression of the gut endocrine gene NT/N. Defining the mechanisms regulating NT/N expression in these hepatic-derived cell lines will provide not only a better understanding of cell-specific and developmental regulation of a gut endocrine gene but also possible insight into liver cell lineage patterns and the derivation of certain hepatocellular cancers.

Distribution of neurotensin-containing neurons in the central nervous system of the pigeon and the chicken

Neurotensin is widely located in neurons of the central and peripheral nervous systems among mammalian species. To obtain a comparative evaluation, we examined the distribution of neurotensin-containing cell bodies and fibers in the central nervous system of the pigeon and the chicken. The pattern of localization of neurotensin immunoreactivity was similar in the two species. Abundant accumulations of neurotensin-containing cell bodies were found in the dorsolateral corticoid area, the piriform cortex, the parahippocampal area, the medial part of the frontal neostriatum, the lateral part of the caudal neostriatum, nucleus accumbens, the bed nucleus of the stria terminalis, ventral paleostriatum, the preoptic area, the ventromedial hypothalamic nucleus, the inferior hypothalamic nucleus, the infundibular hypothalamic nucleus, and the mammillary nuclei. Extremely dense networks of neurotensin-containing fibers were found in the pallial commissure, the lateral septal nucleus, the preoptic area, the periventricular gray around the third ventricle, the dorsalis hypothalamic area, the hypothalamic nuclei, the parabrachial nucleus, the locus ceruleus, and the dorsal vagal complex. Major differences of immunoreactivity between the two species were as follows. 1) The chicken neurohypophysis contained an extremely large accumulation of immunoreactive fibers, but there were few in the median eminence. The reverse was found in the pigeon. 2) The optic tectum in the pigeon contained immunoreactive cells and fibers in layers 2 and 4, but no immunoreactivity was seen in the chicken optic tectum. 3) The cerebellar cortex in the pigeon contained a small number of immunoreactive fibers, whereas that in the chicken did not. 4) The pigeon spinal cord contained immunoreactive neurons in the subependymal layer, but the chicken spinal cord did not. Our observations suggest the presence of a very wide network of neurotensin-containing neurons in the avian brain and spinal cord, which is also the case in mammals.

Calcium regulated chloride permeabilities in primary cultures of rabbit colonocytes

To determine if calcium-dependent secretagogues directly act on epithelial cells to elicit Cl- secretion, their effects on Cl- transport and intracellular Ca(2+) concentrations ([Ca2+]i) were determined in primary cultures of rabbit distal colonic crypt cells. The Cl- sensitive fluorescent probe, 6-methoxyquinolyl acetoethyl ester, MQAE and the Ca(2+)-sensitive fluorescent probe, fura-2AM were used to assess Cl- transport and [Ca2+]i, respectively. Basal Cl- transport (0.274 +/- 0.09 mM/sec) was inhibited significantly by the Cl- channel blocker diphenylamine-2-carboxylate (DPC, 50 microM, 0.068 +/- 0.02 mM/sec; P < 0.001) and the Na+/K+/ 2Cl- cotransport inhibitor furosemide (1 microM, 0.137 +/- 0.04 mM/sec; P < 0.01). Ion substitution studies using different halides revealed the basal influx to be l- > F- > or = Cl- > Br-. DPC inhibited l- influx by approximately 50%, F- influx by 80%, Cl-influx by 85%, and Br- influx by 90%. Furosemide significantly inhibited influx of Br- (84%) and Cl- (81%) but not of F- and l-. The effects of agents known to alter biological response by increasing [Ca2+]i in other epithelial systems were used to stimulate Cl- transport. Cl- influx in mM/second was stimulated by 1 microM histamine (0.58 +/- 0.05), 10 microM neurotensin (2.07 +/- 0.32), 1 microM serotonin (1.63 +/- 0.28), and 0.1 microM of the Ca2+ ionophore A23187 (2.05 +/- 0.40). The Cl- permeability stimulated by neurotensin, serotonin, and A23187 was partially blocked by DPC or furosemide added alone or in combination. Histamine-induced Cl- influx was significantly inhibited by only furosemide. Indomethacin blocked histamine-stimulated Cl- permeability but had no effect on the actions of the other agents. These studies, focusing on isolated colonocytes without the contribution of submucosal elements, reveal that (1) histamine stimulates Cl- transport by activating the Na+/K+/2Cl- cotransporter via a cyclooxygenase-dependent pathway; (2) neurotensin, serotonin, and A23187 activate both Cl- channels and the cotransporter, and their actions are cyclooxygenase-independent.

Fetal and neoplastic expression of the neurotensin gene in the human colon

OBJECTIVE

The authors identified various colon cancers that express the gene for the gut peptide neurotensin (NT/N). In addition, the authors sought to delineate the temporal pattern of NT/N gene expression in the human fetal colon.

SUMMARY BACKGROUND DATA

Expression of NT/N is localized to the mucosa of the adult small bowel but also has been identified in the fetal colon, which resembles the small bowel until the end of the second trimester. Ectopic NT/N expression has been shown in certain types of colon cancer, suggesting a reversion to a fetal phenotype.

METHODS

Sensitive ribonuclease protection assays were used to determine NT/N expression in colon cancers and adjacent normal mucosa as well as colon cancers established as tumor xenografts and fetal colon samples.

RESULTS

NT/N gene expression was shown in 4 of 12 (25%) human colon cancer xenografts and in 11 of 40 (28%) freshly resected colon adenocarcinomas; NT/N gene expression was not expressed in any of the samples of normal colonic mucosa adjacent to the tumors. The NT/N gene was expressed maximally in the fetal colon between 16 and 18 weeks' gestation; NT/N expression was decreased between 19 and 22 weeks and was not apparent in either the 24-week fetal colon or the adult samples.

CONCLUSIONS

The NT/N gene expression is expressed transiently in the fetal colon during a development stage that is characterized by morphologic similarity to the small bowel. In addition, NT/N is reexpressed in approximately one fourth of the human colon cancers, indicating that neoplastic transformation leads to reversion to a fetal phenotype in certain types of colon cancer. The NT/N gene will provide a useful model to further define the complex differentiation pathways in the normal gut as well as the process of fetal "dedifferentiation" in certain types of colon cancer.

Kinetics of neurotensin gene expression in the developing gut

BACKGROUND

Expression of the gene encoding neurotensin (NT/N) is regulated in a strict temporal- and spatial-specific pattern during gut development; the mechanisms (that is, transcriptional versus posttranscriptional) responsible for this expression pattern are not known. The purpose of this study was to determine whether developmental changes in NT/N expression reflect alternations in gene transcription.

METHODS

Sensitive ribonuclease protection assays were performed with a rat NT/N genomic probe containing the entire sequence of both exon 1 and intron 1 hybridized with RNA from fetal (day 19) and postnatal (days 14, 28, and 60) rat jejunum and ileum; signals were quantitated densitometrically.

RESULTS

Mature (exon 1) and precursor (exon 1 + intron 1) NT/N RNA, initially low in the fetus, increased dramatically by postnatal day 14 and attained maximal levels by day 28. NT/N RNA levels remained stable in the ileum of the 60-day-old rat but decreased in the jejunum, consistent with the typical expression pattern in the gut.

CONCLUSIONS

Concomitant changes in expression of precursor and mature NT/N RNA suggest that NT/N gene regulation occurs at the level of transcription in the gut during development. Identifying the factors that regulate NT/N gene transcription is crucial to our understanding of how neurotensin functions in the gut.

Neurotensin binding to human embryonic lung fibroblasts

Several neuropeptides have been shown to regulate the function of cells involved in immune response and inflammation. Neurotensin is a 13 amino acid neuropeptide localized primarily to the nervous system and gut. Neurotensin also stimulates mast cell degranulation and enhances phagocytic and cytolytic capability of macrophages, suggesting that this peptide regulates inflammatory and immune responses. Fibroblasts play an important role in inflammation and tissue healing, and these processes may be regulated by several neuropeptides that have been shown to bind to fibroblasts. However neurotensin receptors have not been identified on fibroblasts. Human embryonic lung fibroblasts (HELF) were examined for binding and biological effects of neurotensin. 125I-neurotensin binding to adherent and confluent human embryonic lung fibroblasts (HELF), plated in 12mm diameter wells was specific and saturable. Computer-assisted resolution of the binding data demonstrated two classes of binding sites: a high affinity, low capacity site (Kd = 1.6 x 10(-11) M, 19.5 x 10(7) sites/well), and a low- affinity, high-capacity site (Kd = 10(-8) M, 4 x 10(9) sites/well). Neurotensin stimulated immediate, transient, dose-dependent increases of cytosolic calcium in HELF (threshold dose: 10(-11) M), suggesting release of calcium from intracellular stores. The novel finding of neurotensin receptors on fibroblasts provides further support for this neuropeptide's role as a regulator of inflammatory and immune responses.

Modulatory action of neurotensin on the pituitary-adrenocortical function in rats: evidence for an acute dose-dependent biphasic effect

Adult female rats were sc injected with 0.6 or 1.2 nmol/100 g body wt of neurotensin (NT); control animals received a sc injection of saline vehicle. The plasma concentrations of ACTH, aldosterone and corticosterone were measured 1, 2 or 4 h after the injection. Our RIA estimates revealed that the lower dose of NT exerted a net stimulatory effect on the rat pituitary-adrenocortical function, that can be ascribed to the well-known NT-evoked enhancement of CRH release. Conversely, the higher dose of NT appeared to have a marked inhibitory effect on both pituitary ACTH release and adrenocortical secretion. The mechanism underlying this last action of NT remains to be elucidated.

Plasma neurotensin: lack of a differentiation and tumor marker in children with neuroblastoma

Neurotensin is a tridecapeptide with changing receptor expression in central and peripheral neural cells during ontogeny suggesting its potential use as a differentiation and tumor marker in neuroectodermal malignancies. We investigated the neurotensin levels in plasma samples of 58 patients with neuroblastoma using a sensitive radioimmunoassay. Elevated levels were found only in one stage III and in one stage IVs patient, while the neurotensin concentrations of 56 patients were in the range of control children. We conclude that plasma neurotensin reflects neither the differentiation nor the tumor status in children with neuroblastoma.

Tissue distribution and innervation pattern of peptide immunoreactivities in the rat pancreas

The distribution of calcitonin gene-related peptide (CGRP), substance P/tachykinin (SP/TK), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY) and gastrin-releasing peptide (GRP) immunreactivities (IR) in the rat pancreas was investigated using radioimmunoassay and immunohistochemistry. CGRP, NPY and VIP tissue contents are much higher than GRP and SP/TK concentrations. Peptide-containing nerves are distributed to both the exocrine and endocrine pancreas. However, differences exist in terms of density and targets of innervation for each peptidergic system. In the acini and through the stroma, fibers IR for CGRP, NPY and VIP are greater than GRP- and SP/TK-containing processes. The vasculature is supplied by a prominent NPY, CGRP and, to a lesser extent, SP/TK innervation. VIP-IR is found occasionally, and GRP-IR is never detected, in fibers associated with blood vessels. Around ducts, CGRP- and NPY-positive neurites are greater than SP/TK- greater than or equal to VIP-IR fibers, whereas GRP-containing nerves are not visualized. In the islets, the density of peptidergic nerves is: VIP-, GRP- greater than or equal to CGRP-IR greater than NPY or SP/TK. In intrapancreatic ganglia. VIP- and, to a lesser extent, NPY-IRs are found in numerous neuronal cell bodies and in nerve fibers; GRP-IR is present in numerous nerve processes and in few cell bodies; CGRP- and SP/TK-IRs are detected only in fibers wrapping around unlabeled ganglion cells. The majority of CGRP-IR fibers contain SP/TK-IR. The existence of differential patterns of peptidergic nerves suggests that peptides exert their effects on pancreatic functions via different pathways.

Neurotensin enhances plasma adrenocorticotropin concentration by stimulating corticotropin-releasing hormone secretion

The systemic administration of neurotensin (NT) dose-dependently increased plasma adrenocorticotropin (ACTH) concentration in rats, and this effect was annulled by (alpha-helical)-CRH9-41, an antagonist of corticotropin-releasing hormone (CRH). The systemic administration of [D-Trp11]-neurotensin (NT-A), a specific NT antagonist, dose-dependently reduced the basal level of circulating ACTH, and this effect was blunted by NT injection. The ACTH inhibitory action of NT-A was completely overcome by the administration of CRH. Taken together, our findings suggest that NT plays a physiologic role in rats, as ACTH secretagogue, and that the mechanism underlying this action of NT involves the stimulation of CRH release.

Effects of neurotensin on the pituitary-adrenocortical axis of intact and dexamethasone-suppressed rats

A 7-day infusion with neurotensin (NT) (10 micrograms.kg-1.day-1) stimulated adrenal growth in intact female rats, and raised ACTH blood concentration, without altering corticosterone (B) plasma level and output by adrenal homogenates. For a week dexamethasone (Dx) administration (125 micrograms.kg-1.day-1) caused a notable adrenal atrophy, a marked lowering of ACTH and B blood concentrations, and a profound depression of B output by adrenal homogenates. NT infusion reversed Dx-induced adrenal atrophy and plasma ACTH-level drop, but not the impairment in adrenal-cortex secretory activity. In vitro studies showed that NT (10(-6) mol/l) significantly reduced basal, but not ACTH-stimulated B release by isolated rat inner adrenocortical cells. These findings suggest that NT exerts a direct inhibitory effect on B production by rat adrenals, while it is able to enhance ACTH secretion and consequently adrenal growth. Moreover, they indicate that NT evokes a striking, and at present unexplained dissociation between structure and function in the adrenal cortex of Dx-suppressed rats.

Neurotensin is localized to paracrine cells in the urinary bladder of the turtle, Chrysemys picta

Urinary bladder from the painted turtle, Chrysemys picta, contains a substantial population of endocrine/paracrine cells scattered through the mucosal epithelium which immunostains using antisera directed toward mammalian neurotensin (NT). Radiommunoassay of 0.1 N HCl extracts of Chrysemys bladder indicated an immunoreactive NT (iNT) concentration of 161 +/- 39 pmol/g tissue (n = 9), an amount lower but comparable in magnitude to that found in mucosal scrapings of the intestine (926 +/- 125 pmol/g, n = 9). Bladder and intestinal iNT were indistinguishable during chromatography on Sephadex G-25 and HPLC on mu-Bondapak C18 where they eluted at the same position as avian NT. Similar results were obtained by immunocytochemistry and radioimmunoassay of urinary bladders from Pseudemys scripta scripta, P. scripta elegans, and P. floridana, three emydid species closely related to C. picta, but not from Sternotherus odoratus and Trionyx spinifer asper, representatives of the families Kinosternidae and Trionychidae, respectively, although positive results were obtained with intestinal preparations from these species. NT cells were not seen in urinary bladder from Rana pipiens, Bufo marinus, Necturus maculosus, or Anolis carolinensis. Thus, the presence of NT-containing cells in urinary bladder is not common among subavian vertebrates and may even be restricted to the Emydidae family of chelonians.

Mutually dependent response elements in the cis-regulatory region of the neurotensin/neuromedin N gene integrate environmental stimuli in PC12 cells

The expression of the gene encoding the neuroendocrine peptides neurotensin (NT) and neuromedin N is strictly dependent on simultaneous exposure to multiple inducers in PC12 pheochromocytoma cells. NT peptide and NT/N mRNA levels are synergistically induced by combinations of NGF, dexamethasone, activators of adenylate cyclase, and lithium ion. We have used transient transfection assays to delineate the rat NT/N gene sequences necessary for this complex regulation. Progressive deletions of the 5' flanking region revealed that sequences between -216 and +56 are sufficient to confer the full spectrum of responses exhibited by the endogenous gene to a reporter gene. Detailed mutational analysis of this region indicates that it is composed of an array of inducible cis-regulatory sequences, including AP-1, cAMP response, and glucocorticoid response elements. Specific mutation of either the AP-1 site or each of two cAMP response elements indicates that they are functionally interdependent. This array of response elements serves to integrate multiple environmental stimuli into a unified transcriptional response.

Synaptic organization of neurotensin immunoreactive amacrine cells in the chicken retina

Immunohistochemistry was utilized to investigate the light and electron microscopic localization of neurotensinlike immunoreactive (NT) amacrine cells in the chicken retina. The NT cells possess oval cell bodies (7 microns in diameter) that are located in either the second or third tier of cells from the border of the inner nuclear and inner plexiform layers. The processes of such cells extend into the inner plexiform layer where they ramify as a narrow plexus in sublamina 1 and as a broad plexus in sublaminas 3 and 4. Additionally, stained processes are observed occasionally within sublamina 5. At the ultrastructural level, NT-positive somas exhibit a rather dense and evenly distributed peroxidase reaction product throughout their cytoplasm. The nucleus of NT amacrine cells possess a round, unindented nuclear membrane. NT-immunoreactive processes in the inner plexiform layer interact synaptically only with non-NT cells. NT processes receive synaptic input mainly from the processes of amacrine cells and to a lesser degree from bipolar cells. The large majority of NT-stained varicosities form presynaptic contacts onto the processes of amacrine cells, but are also presynaptic to bipolar cell axon terminals. Moreover, each of the above synaptic relationships can be identified in each of sublaminas 1 and 3 to 4 of the inner plexiform layer. In addition, NT processes are presynaptic to processes devoid of synaptic vesicles that may originate from ganglion cells. Finally, NT processes occasionally form synaptic contacts onto somas situated in the most proximal row of the inner nuclear layer.

Effects of cholera toxin, Escherichia coli heat stable toxin and sodium deoxycholate on neurotensin release from the ileum in vivo

Neurotensin (NT) is a biologically active peptide found in specialized epithelial cells (N-cells) in the distal small intestine. In this study we tested the hypothesis that NT may be released by luminal secretagogues, i.e., cholera toxin, Escherichia coli heat-stable toxin and sodium deoxycholate. Cholera toxin elicited net fluid secretion in anesthetized cats. This secretion was accompanied by an increased release of NT-like immunoreactivity (NTLI) into the mesenteric vein when NTLI was measured with either a C-terminally or a N-terminally directed antibody. An increasing plasma NTLI concentration (N-terminally directed antibody) was recorded in the mesenteric vein and femoral artery in cholera experiments. These results indicate that cholera toxin releases NT from the small intestine. Since neurotensin causes intestinal fluid secretion at least in part via an activation of enteric nerves we propose that the N-cell functions as a 'receptor cell' which activates an intramural secretory reflex upon luminal stimulation by cholera toxin. This study does not support a similar role for NT in the secretion elicited by the heat stable toxin of Escherichia coli or by sodium deoxycholate since we were unable to demonstrate any intestinal release of NTLI after exposing the intestine to these secretory agents.

Distribution pattern of cell bodies and fibers with neurotensin-like immunoreactivity in the cat hypothalamus

Neurotensin is widely distributed in the central and peripheral nervous systems. Extensive radioimmunoassay and immunohistochemical studies in rats show that the neurotensin immunoreactive perikarya and fibers are most prominent in the hypothalamus. Radioimmunoassay studies have suggested that the levels of neurotensin in the hypothalamus of cats may be six times higher than that of rats. We studied the distribution pattern of neurotensin immunoreactivity within the hypothalamus of the cat by avidin-biotin modification immunohistochemical methods: (1) to define its distribution pattern within the hypothalamus, and (2) to compare our findings with the patterns that have been described in rats. Results show that neurotensin immunoreactive cell bodies and fibers are most prominent in the rostral and intermediate regions of the cat hypothalamus. Cell bodies with neurotensin-like immunoreactivity are seen maximally in the medial preoptic region, the infundibular nucleus, and the lateral hypothalamus. The neurotensin positive fibers are dense in the periventricular regions of the entire rostro-caudal extent of the hypothalamus. This pattern of distribution of neurotensin immunoreactivity is similar to that described in rats. The suprachiasmatic nuclei of the cat hypothalamus, however, contained a significant number of neurotensin immunoreactive cell bodies, an observation not noted in the rat hypothalamus. The neurotensin immunoreactive neurons were more numerous in the lateral hypothalamus than has been reported in rats, but the paraventricular nucleus of the hypothalamus in cats contained fewer neurotensin immunoreactive perikarya. The presence of neurotensin immunoreactive perikarya in the suprachiasmatic nucleus and the apparent increase in the number of neurotensin immunoreactive neurons in the lateral hypothalamus may account for the increased levels of neurotensin reported in cats. Neurotensin has been speculated to play a role in nociception, thermoregulation, and control of arterial pressure by acting as a hormone or a neurotransmitter. Details of the pattern of colocalization of neurotensin with that of other neuropeptides and neurotransmitters will aid in our understanding of its role in these functions.

Neuropeptide (neuropeptide Y, neurotensin, vasoactive intestinal polypeptide, substance P, calcitonin gene-related peptide, somatostatin) immunohistochemistry and ultrastructure of renal nerves

With the use of several region-specific antisera and the peroxidase-antiperoxidase (PAP) technique, several regulatory polypeptides were localized in nerves of the kidney. Neuropeptide Y (NPY)- immunoreactivity (IR), neurotensin (NT)-IR and vasoactive intestinal polypeptide (VIP)-IR occurred at high densities in all segments of the renal arterial system forming a perivascular plexus. Furthermore, NT-IR nerves were particularly frequent at the juxtaglomerular apparatus (JGA). Calcitonin gene-related peptide (CGRP)-IR was mainly concentrated in nerves supplying the hilus arteries and the JGA. Substance P (SP)-IR was predominantly found in large varicosities close to large renal arterial vessels and in the vicinity of the JGA. Somatostatin (SOM)-IR was only observed in single varicosities located at the media-adventitia border of large renal hilus arteries. The peptidergic nerves are correlated to their ultrastructural counterpart. In addition, the distribution patterns and the frequency of the different types of renal peptidergic nerve fibres are evaluated and compared. The functional role of these neuropeptides and their origin within the efferent branch of this part of the peripheral autonomic nervous system is discussed. Furthermore, the implication of some of the neuropeptides studied in afferent renal innervation is also substantiated.

Precursor forms of neurotensin (NT) in cat: processing with pepsin yields NT-(3-13) and NT-(4-13)

Basic proteins present in 0.1 N HCl extracts of feline CNS and intestine were found to liberate immunoreactive neurotensin (iNT) when treated with hog pepsin. These protein substrates were separated using Sephadex G-25, Sephadex G-75 and reverse-phase HPLC. In a calibrated SDS-polyacrylamide gel electrophoresis system, the major substrate from cat ileum exhibited a molecular weight of ca 16 kDa and minor substrates were observed at 30, 40 and 65 kDa. As shown previously for synthetic NT, pepsin-treatment of feline ileal NT converted it into the fully immunoreactive NT-(4-13) fragment (yield, 95%). When treated with pepsin, the partially purified ileal substrates gave rise to 4 immunoreactive peptides, one of which (ca 15% of total) eluted with the same retention time as NT-(4-13) while the major peptide formed (ca 40% of total) eluted near to the position of NT-(3-13). Both these products reacted equally well with two different antisera towards the C-terminal 5- and 8-residues of NT and were not recognized by an N-terminal antiserum. Experiments using various proteases demonstrated that the NT-related sequence(s) were located internally in each substrate and suggested that they were bounded by double basic residues. Substrate activity in isotonic homogenates of feline spinal cord, brain, adrenal and ileum cosedimented with iNT during equilibrium centrifugation, apparently in association with vesicle and/or synaptosomal particles. These findings indicate that basic proteins, colocalized with NT in vesicle-like particles of CNS, adrenals and ileum, could serve as precursors to this peptide, being liberated by pepsin-related enzyme(s).

Neurotensin in the human brain

The localization of neurotensin-immunoreactive sites in the adult human brain was investigated by the indirect immunoperoxidase method of Sternberger [Sternberger (1979) Immunocytochemistry. Wiley, New York]. Our results demonstrate a widespread, albeit uneven occurrence of neurotensin-immunoreactive cells and processes throughout the central nervous system. Immunoreactive cells are prominent in the medial hypothalamus and in various regions of the limbic system, including the amygdaloid body, septal area, bed nucleus of the stria terminalis and piriform cortex. A few cells were also found in the dorsal synencephalon, superior colliculus, periaqueductal grey and spinal trigeminal nucleus. The distribution of immunoreactive fibres corresponds well with that reported for rodents. Areas with the highest concentration of neurotensin-immunoreactive processes included all the areas where immunoreactive neurons were found and, in addition, periventricular thalamic nuclei, the sublenticular region, lateral parts of the brainstem reticular formation and the vagus-solitarius complex. Comparison mapping studies of melanin-containing neurons on sections treated with neurotensin antiserum revealed an anatomical relation between almost all the catecholaminergic cell clusters with peptide-containing fibres.

The effect of neurotensin on pure pancreatic secretion in man

The effect of neurotensin on human pancreatic secretion and its role in the control of pancreatic function are not well defined. In the present investigation I have studied the effect of low doses of neurotensin on pure pancreatic secretion in six subjects with external transduodenal drainage of the main pancreatic duct performed after biliary tract surgery. Intravenous infusion of neurotensin at doses of 0.5 and 2.5 pmol X kg-1 X min-1, administered during submaximal pancreatic stimulation with secretin and cerulein, caused a significant and dose-dependent stimulation of pancreatic secretion (volume, bicarbonate, and protein). The effect of neurotensin was rapid, persisted for the duration of neurotensin infusions, and ceased immediately when the administration of the peptide was discontinued. Compared with control values, the increase in bicarbonate output averaged 24.8% and 44.8% and the increase in protein output 29.2% and 54% for the two different doses of neurotensin used, respectively. The clear effectiveness of the small doses of neurotensin used in the present study strongly suggests that the stimulatory effect of the peptide on pancreatic secretion may be of physiologic significance.

Neurotensin-like immunoreactivity in the pituitary and hypothalamus of bony fishes

Using an antiserum raised against synthetic neurotensin (NT), the distribution of immunoreactivity in the pituitary and hypothalamus has been examined by immunocytochemistry at light and electron microscope level in a number of species of bony fishes. In most species immunoreactive perikarya were found in the preoptic region of the hypothalamus, with fibres throughout the tuberal hypothalamus and neurohypophysis (neural lobe and median eminence). In the neurohypophysis of teleosts NT-like immunoreactivity was seen in a dense band of fibres bordering the ACTH cells of the rostral pars distalis: absorption controls showed that this was due to the presence of an NT(8-13)-like or xenopsin-like sequence, which, according to electron microscopic observations, was contained in small dense cored vesicles. The antiserum also stained the pituitary ACTH cells of some species, apparently due to cross-reaction with the 17-19 sequence of ACTH. These results suggest that an NT-like peptide may have a role in control of the adenohypophysis in fishes.

Peptidergic innervation of the human and guinea pig uterus

The peptidergic innervation of the human and guinea pig uterus was studied using immunohistochemical methods. Antibodies against several peptides were applied for the PAP-technique to stain peptidergic nerves specifically. These are located in the adventitia of large uterine vessels in the myometrium and smaller vessels of the myometrium and endometrium. A differential distribution of the individual peptides was observed for VIP-IR (vasoactive intestinal polypeptide immunoreactivity), NPY-IR (neuropeptide Y), SP-IR (substance P), SOM-IR (somatostatin) and NT-IR (neurotensin) nerve fibers. Specific functional implications for these neuropeptides can be derived from their histochemical location.