Ghrelin, a recently discovered peptide hormone, is primarily produced by endocrine cells in the oxyntic mucosa of rat and human stomachs  and . Ghrelin has also been found in the small intestine, pancreas, liver, kidney, placenta, testis, ovary, pituitary gland and hypothalamus in both humans and rodents  and . Ghrelin is the natural ligand for the growth hormone secretagogue receptor (GHSR) and its receptor is found all over the body including in the bowel, pancreas, stomach, heart, lungs and brain ,  and . Besides stimulating growth hormone secretion, studies show that ghrelin exerts a number of central and peripheral actions such as regulation of food intake, control of energy balance, glucose metabolism and insulin release, cardiovascular actions, stimulation of gastric Pyronaridine Tetraphosphate secretion, and motility , , ,  and . Because of the presence of ghrelin and its receptors in the stomach, it would be reasonable to expect its participation to gastric function. In fact, a number of studies have provided evidence of a close relationship between ghrelin and gastric motility , ,  and . Recent studies have indicated that ghrelin (5 μg/kg–50 μg/kg) enhances gastric motility and gastric emptying in rodents and dogs, stimulates small intestinal transit, and reverses postoperative gastric ileus ,  and . However, it has been also reported that ghrelin has no effect on gastric emptying in humans  and does not stimulate gastrointestinal motility in the dog . In addition, Masuda et al.  reported that the increasing effect of ghrelin (0.8–20 μg/kg i.v.) on gastric motility was completely eliminated by pretreatment with atropine or by bilateral cervical vagotomy. Interestingly, a recent study demonstrated that intravenous administration of ghrelin (0.1–10 μg/kg) induced fasting-like motor activity in both the stomach and the duodenum in vagotomised rats . It is known that gastric motility is regulated by gastric myoelectrical activity (GMA), which consists of gastric slow wave and spike potential . Electrogastrography (EGG) is a technique for recording gastric myoelectrical activity, which can be measured using one of three methods: cutaneous electrodes, intraluminal electrodes, or serosal electrodes. Serosal electrodes give the most reliable recording, which reflects detailed information on GMA. However, this is suitable only for experimental studies on animal models . Chen and McCallum  reported that normal slow wave frequency in the EGG was related to normal gastric motility and that abnormal slow wave frequencies were associated with motility disorders. It is clear that the mechanism of ghrelin-induced changes in gastrointestinal motility has not been fully understood. Therefore, the principal objective of this study was to investigate the pharmacological role of ghrelin on gastric myoelectrical activity in rats. A secondary objective was to study the role of ghrelin on the gastric emptying rate of a non-caloric liquid meal in conscious rats. In addition, atropine sulfate was administered subcutaneously before the ghrelin injection to investigate whether cholinergic activity is involved in the effect of ghrelin.
Previous studies revealed the importance of the third intracellular loop of glucagon-like peptide-1 Biotin NHS (GLP-1R) in coupling to Gs and Gi1 proteins. In order to further study the signaling mechanisms of GLP-1R, we tested three peptides, corresponding to the sequences of the first (IC1), the second (IC2), and the third (IC3) intracellular loop of GLP-1R, for their interactions with heterotrimeric G-proteins of different types (Gαs, Gαo, Gαi1, and Gα11 plus Gβ1γ2) overexpressed in sf9 cells. IC3 peptide powerfully stimulates all types of tested G-proteins, whereas IC1 and IC2 peptides show differential effects on G-proteins. Both IC1 and IC2 peptides activate Gs and cooperate with IC3 peptide in its stimulation. Go is not affected by IC1 and IC2. Gi1 and G11 are not affected by IC1, but are activated by IC2, which in activation cooperates with IC3. We suggest that GLP-1R is not coupled only to Gs and Gi1, as shown previously, but also to Go and G11. IC3 loop is the main switch that mediates signaling via GLP-1R to G-proteins, while IC1 and IC2 loops are important in discrimination between different types of G-proteins.
Recently, a potential therapeutic role for GLP-2, based on its intestinotrophic effects, was demonstrated in patients with short bowel syndrome  and this pharmacologic potential of the peptide has increased interest in its pharmacokinetics of GLP-2. In vivo, intact GLP-2 (1–33) is degraded from its NH2-terminal by cleavage of two Pepstatin A by the widely distributed serine protease dipeptidyl peptidase IV (DPP-IV), producing the truncated fragment GLP-2 (3–33) ,  and . This cleavage of a dipeptide from GLP-2 (1–33) might be crucial for the peptide’s biologic activities, since previous studies with GLP-2 and other members of the proglucagon-derived peptides (PGDPs), i.e. GLP-1, have suggested that the NH2-terminal is important for signal transduction, whereas the C-terminus seems to be more important for the correct folding of the peptide ,  and . Concordant with this, recent data have indicated that the truncated fragment, GLP-2 (3–33), interacts with the GLP-2 receptor  and , but it remains unclear whether GLP-2 (3–33) possesses in vivo activity per se or has any influence on the biologic activity of GLP-2 (1–33), e.g. by competitive interaction.
1 × 106 MΦ/well were incubated in the dark with 10 μM 2′,7′-dichlorofluorescein diacetate (DCF-DA) in serum-free medium for 30 min at 37 °C. DCF-DA diffuses through the cell membrane and is hydrolyzed by intracellular esterases to nonfluorescent DCF deacetylated, which is then rapidly oxidized to highly fluorescent DCF in the presence of ROS. The DCF fluorescence intensity is proportional to the amount of intracellular ROS formed . After the incubation with the fluorescent dye, S peptide tag were then harvested and the medium containing the unincorporated dye was eliminated by centrifugation. Cells were then stimulated in serum-free medium with different BNP concentrations (10− 8–10− 10 M) for different experimental times (3–9 h). In those experiments involving diphenylene iodinium (DPI), a NADPH oxidase inhibitor, cells were incubated with 10− 8 M DPI for 30 min before BNP addition. At each timepoint, cells were harvested, resuspended in phosphate buffered-saline (PBS), and assessed for changes in fluorescence using a background-controlling computer-aided LS-50b fluorescence spectrometer (Perkin Elmer) with excitation wavelength set at 485 nm and emission wavelength set at 530 nm, using 5 and 10 nm slits for each light path, respectively. Results were expressed as fluorescence intensity, reported as Fluorescence Units (F.U.), in respect to cells loaded with only DCF-DA (C).
Abstract Keywords Parathyroid hormone-related protein; LoVo (colon cancer cells); Extracellular matrix; Proliferation; Adhesion; Integrins 1. Introduction It was originally thought that PTHrP was only produced by certain cancers associated with HHM. More recently, the protein was found to be distributed in most fetal and adult tissues, including the gut mucosal epithelium ,  and . PTHrP is also expressed by cancer 3X FLAG not typically associated with hypercalcemia, such as those of the colon and prostate , , , , , ,  and , and has been shown to play a role in cancer cell proliferation, survival, extracellular matrix (ECM) adhesion, migration and invasion , ,  and . Widespread expression of PTHrP and PTH/PTHrP receptor genes and proteins has been found in gut villus epithelium  and , suggesting a local regulatory role for PTHrP acting via an autocrine/paracrine mechanism. In addition, endogenous overexpression of PTHrP in the IEC-6 rat intestinal crypt cell line significantly enhanced cell growth via an intracrine pathway .
The local ethics committee for animal experimentation in northern Stockholm, Sweden, approved the experimental protocol. Data are presented as mean±S.E.M. or mean±S.D. as indicated. The Epoxomicin and pharmacokinetic parameters were computed by non-compartmental analysis using the WinNonlin 4.1 software (Pharsight, Mountain View, CA, USA). The plasma peptide concentration–time profile was calculated according to a third-degree polynomial. The area under the curve (AUC) was calculated by the linear trapezoidal rule from top concentration to the last detectable concentration C (t60) at time 60 min. Plasma peak drug concentration (Cmax) and time to reach Cmax (tmax) were obtained directly from the experimental data. The terminal elimination rate constant (k) was derived by the slope of the linear regression curve obtained by fitting the natural logarithms of the terminal concentration values versus time. The terminal elimination half-life (t1/2) was calculated as ln 2/k. The apparent total body clearance CL/F was calculated using the formula D/AUC and the volume of distribution Vd/F using the formula D/AUCk. Statistical evaluation was carried out using the non-parametric Friedman’s test for comparisons between multiple groups, or the Mann–Whitney U test for comparisons between two groups. P<0.05 was considered statistically significant.
3.2. The medulla (levels 2–15) 3.3. The pons and caudal midbrain (levels 16–32) 4. Discussion The results of this study suggest that NPY cell bodies were distributed in discrete areas of the brainstem. The topographic patterns of the NPY mRNA localization include the following: (1) the nSG/nNV (levels 1–7), (2) the dorsal ventral tegmentum of the medulla, including the nTS complex (levels 4–14), (3) the ventral lateral tegmentum of the medulla, including the nRL and reticular formation (levels 6–14), (4) the LC and nR (levels 21–26) and (5) the lateral tegmentum of mesencephalon, including the periaqueductal grey and nDR (levels 28–31). The role of NPY Z-VEID-FMK in the nTS and nRL is largely unknown. However, the colocalization of NPY and catecholamines in these areas suggests that NPY may modulate the activity of these catecholaminergic neurons. Numerous studies have shown that NPY has similar effects in the central nervous system as norepinephrine 9 and 13and may alter the activity of alpha-2 adrenergic receptors . Moreover, the neural projections of the nTS and nRL to the hypothalamus and other brain areas have been well established in the rat 2, 3 and 8. The nTS/nRL-hypothalamic connections are believed to be a major pathway by which NPY and norepinephrine regulate the release of reproductive hormones 29 and 30. The nTS also receives projections from the hypothalamus, basal nucleus of striatum and amygdala ; these projections may constitute a feedback circuit between the brainstem and the forebrain.
Pig ovary was obtained from slaughter house and was kept in physiologic saline at 4 °C. Granulosa Hexa His and follicular fluid from medium-sized follicles (1–3 mm) were gently collected into a small bottle kept at 4 °C through 23G needle connected with vacuum pump. Granulosa cells were separated from follicular fluid by centrifugation at 200×g for 10 min at 4 °C and washed twice with HEPES buffer. After cell counting, granulosa cells were reconstituted with warm HEPES buffer up to 8×107 cells/ml. The composition of the HEPES buffer solution was as follows: 118 mM NaCl, 4.7 mM KCl, 2.5 mM CaCl2, 1.2 mM MgSO4, 25 mM NaHCO3, 10 mM HEPES, 10 mM glucose and 0.1% bovine serum albumin (BSA). Three hundreds microliters of cell suspension was divided into each well (8×6 well plate), and various concentrations of natriuretic peptides were added. After incubation for 20 min at 37 °C, incubation medium was centrifuged at 10,000×g for 10 min at 4 °C. The amount of ANP secreted from granulosa cells and the cGMP production in granulosa cells were measured by radioimmunoassay (RIA), as described below. All experiments were performed in triplicate.
The role of particular NPY Y receptors in the 3X FLAG Peptide and in the periphery was extensively investigated during the last two decades, and is still a subject of controversy. However, a specific involvement of various NPY Y receptors in clearly characterized physiological systems by PP-fold protein family members could be outlined. The NPY Y1 receptor intercedes appetitive behavior in the brain  whereas it mediates vasoconstriction in the periphery . The NPY Y2 receptor is involved in suppression of transmitter release  and  and feeding behavior , while the NPY Y2 receptor in the gut mediates antisecretory activity . The NPY Y3 receptor or other additional Y receptors are likely to be involved in mediating the effects of NPY on heart and adrenal glands ; the Y4 receptor has been related to the regulation of the secretion and motility of the gut , and brain Y5 receptors to feeding, epileptogenesis and anxiety behavior  and . Apart from the proposed dose-, time- and receptor-specific effects of NPY on macrophage functions, the selective cleavage of NPY by peptidases  most likely represents another level of regulation within the NPY-macrophage interplay . Dipeptidyl-peptidase IV (DPIV, CD26, EC 126.96.36.199), a serine ectoprotease that is upregulated on activated T cells, other immunocytes , as well as endothelial cells  and , converts NPY to the biologically active Y2 and Y5 receptor agonist NPY3-36. In line with this physiological role of DPIV, we have shown recently that the inhibitor Ile-thiazolidide  potentiated the NPY Y1 receptor mediated pro-inflammatory action of NPY in vivo in the rat  indicating a prolonged in vivo action of the full-length NPY peptide.
Although direct transport across the BBB was prematurely ruled out, other mechanisms were added to the list of ways in which the CNS and GI tract can communicate. Substances can reach parts of the x-press tag where the blood vessels do not form barriers, but are leaky as is typical of peripheral capillary beds. These circumventricular organs act as emetic centers and regulators of thirst  and . Additionally, amylin exerts its anorectic effects  through one of the circumventricular organs, the area postrema . Other GI peptide hormones, such as CCK ghrelin, and adiponectin, may also act in part through circumventricular organs. However, most work in this area agrees that a layer of cells forms a barrier between the circumventricular organs and the adjacent brain parenchyma, thus preventing substances entering the circumventricular organs from leaking into other brain regions. Circulating substances can also affect brain function indirectly by altering the blood level of a second substance which could cross the BBB. For example, insulin by lowering blood glucose levels and ACTH by elevating serum glucocorticoids can each affect a variety of CNS functions.