Porcine Vasoactive Intestinal Peptide Research Articles

Membrane currents elicited by porcine vasoactive intestinal peptide (VIP) in follicle-enclosed Xenopus oocytes

Membrane currents were recorded from voltage-clamped Xenopus laevis oocytes, surrounded by their enveloping follicular and epithelial cells. Porcine vasoactive intestinal peptide (VIP) generated a membrane current due to an increase in membrane conductance to K+. The VIP current was mimicked by the adenylate cyclase activator forskolin and was potentiated by phosphodiesterase inhibitors, suggesting that adenosine 3',5'-cyclic monophosphate (cyclic AMP) plays a role in mediating the response. Though resembling the follicle's responses to catecholamines and adenosine in ionic basis and apparent mechanism, the response to VIP was not blocked by catecholaminergic or purinergic antagonists, indicating the presence of a specific VIP receptor in the follicle. Among the VIP related peptides, PHM-27 generated similar but smaller K+ currents and porcine secretin and glucagon neither elicited a response nor blocked that to VIP. After treating follicles with collagenase to remove the epithelial and follicular cells the responses to VIP were either substantially reduced or abolished, suggesting that the VIP receptors and K+ channels are both located in the follicular cells.

Effect of synthetic chicken and porcine vasoactive intestinal peptide on pancreatic blood flow in dogs

Studies were conducted in dogs to determine the effect of synthetic chicken and porcine vasoactive intestinal peptide on blood flow and exocrine secretion of the pancreas and on systemic arterial pressure. The stimulatory effect of synthetic chicken vasoactive intestinal peptide on blood flow and exocrine secretion of the pancreas was almost similar to that observed after synthetic porcine vasoactive intestinal peptide stimulation, whereas, synthetic chicken vasoactive intestinal peptide retained only approximately two thirds of the potency of synthetic porcine vasoactive intestinal peptide in its effect on lowering systemic arterial pressure. This study suggests that an increase in exocrine pancreatic secretion may be related to an increase in pancreatic blood flow in response to vasoactive intestinal peptide. This study leads us to speculate that total amounts of splanchnic organ blood flow increased in response to porcine vasoactive intestinal peptide are much more greater than those after chicken vasoactive intestinal peptide stimulation, although we cannot exclude the possibility that porcine vasoactive intestinal peptide may be much more potent in its effect on vasodilatations in peripheral systemic vessels in comparison with chicken vasoactive intestinal peptide.

Molecular forms of peptide histidine isoleucine-like immunoreactivity in the gastrointestinal tract: Nonequimolar levels of peptide histidine isoleucine and vasoactive intestinal peptide in the stomach explained by the presence of a big peptide histidine isoleucine-like molecule

Regional specific antibodies and chromatography were used to analyze the distributions and molecular forms of peptide histidine isoleucine (PHI) and vasoactive intestinal peptide (VIP) in the porcine intestine. Both peptides were present along the entire length of the intestine, the highest concentrations occurring in the colon. Concentrations of PHI immunoreactivity, measured with three different antisera, and VIP immunoreactivity were approximately equal in all parts of the gastrointestinal tract except in the stomach. In the stomach, the concentration of PHI immunoreactivity, measured with the N-terminally directed antibody R8403, although equal to the corresponding VIP concentration, was two to four times higher than the PHI immunoreactivity detected with the two C-terminally directed PHI antisera T33 and T41. Chromatographic analysis on Sephadex G-50 superfine of gastric extracts revealed only one VIP immunoreactive peak that eluted in the same position as the porcine VIP standard, at Kav 0.53. A PHI immunoreactive peak was also detected with the C-terminally directed PHI antisera in the same position as porcine PHI standard. However, with the N-terminally directed PHI antiserum R8403, an additional PHI immunoreactive peak was detected in gastric extracts constituting the predominant form present, and this peak eluted earlier at Kav 0.37. The PHI immunoreactive material that eluted earlier was present in the rest of the intestine in only small amounts. As VIP and PHI are believed to be derived from a common precursor, it is suggested that in the stomach the posttranslational enzymic processing of the precursor is different from that in the other parts of the intestine.

Vasoactive intestinal peptide: a novel stimulator of steroidogenesis by cultured rat granulosa cells.

Vasoactive intestinal peptide (VIP) and VIPergic nerve fibers are present in the ovaries of several mammalian species, suggesting a possible ovarian action of VIP. We have investigated the direct effects of synthetic porcine VIP on rat granulosa cell steroidogenesis in vitro. The cells were obtained from immature, hypophysectomized, estrogen-primed rats, and cultured in a serum-free medium for 24 h in the absence or presence of varying amounts of VIP. Medium steroids were then determined by specific radioimmunoassay. Vasoactive intestinal peptide dose-dependently stimulated progesterone, 20 alpha-hydroxypregn-4-ene-3-one (20 alpha-OH-progesterone), and estrogen production with an approximate ED50 value of 3 X 10(-8) M. Maximum steroid production induced by VIP ranged from 15% to 28% of that seen with maximal follicle-stimulating hormone (FSH) stimulation. In contrast to the ability of FSH to induce luteinizing hormone (LH) receptor formation, treatment with VIP did not increase [125I]iodo-human chorionic gonadotropin (hCG) binding to granulosa cells. The ability of several gastrointestinal peptides, having 17-44% sequence identity to VIP, to stimulate granulosa cell steroidogenesis was also tested. The most closely related peptide, PHM-27 was less effective than VIP, and the least closely related, secretin and glucagon, were ineffective at 10(-6) M. Vasoactive intestinal peptide seems to act at least partly through cyclic 3',5'-adenosine monophosphate (cAMP)-dependent processes: addition of a phosphodiesterase inhibitor significantly potentiated the VIP stimulation of granulosa cell steroidogenesis, and VIP was capable of producing a dose- and time-dependent increase in both intracellular and medium cAMP levels. Vasoactive intestinal peptide stimulation of estrogen production seemed to be a result of increased aromatase activity. The increased progesterone production was associated with increased pregnenolone production, increased rate of conversion of pregnenolone to progesterone via 3 beta-hydroxysteroid dehydrogenase, and decreased metabolism of progesterone via 20 alpha-hydroxysteroid dehydrogenase. These results indicate that VIP exerts a specific action on granulosa cells to increase estrogen and progestin production. The observed direct effects of VIP, coupled with its identification in the ovary, suggest that VIP may be a physiologically important regulator of ovarian activity.

Vasoactive intestinal peptide is a physiological mediator of prolactin release in the rat.

To determine whether VIP functions as a physiological PRL-releasing factor, the effects of immunoneutralization of endogenous vasoactive intestinal peptide (VIP) on the PRL secretory response to suckling and ether stress were assessed. Using a porcine VIP-thyroglobulin conjugate as antigen, a peptide-specific antiserum was generated in a rabbit which bound porcine VIP with a Kd of 5.1 X 10(-11) M and a maximum binding capacity of 1830 ng/ml. In a RIA, this antiserum demonstrated immunoreactive VIP in tissue extracts of various regions of the brain and gastrointestinal tract. IR VIP in extracts of cerebral cortex and hypothalamus coeluted with synthetic porcine VIP on Bio-Gel P-30 column chromatography. Using chronically implanted right atrial catheters for blood sampling to avoid effects of stress and anesthesia, PRL blood levels in normal controls began to rise almost immediately after initiation of suckling from basal values of 3.0 +/- 0.9 ng/ml to reach a plateau of 158.1 +/- 33.5 ng/ml after 40 min. When the VIP antiserum was administered immediately before initiation of suckling, the onset of the PRL response was delayed by 40 min, but PRL levels then rose at a slower rate to reach the plateau level of normal animals approximately 80 min later. When VIP antiserum was administered to rats who had been suckling for at least 1 h, PRL levels fell from a mean basal elevated level of 152.7 +/- 16.0 ng/ml to a nadir of 50.4 +/- 9.1 ng/ml 80 min after injection and then gradually returned to basal levels. The effect of VIP antiserum was studied in rats in whom PRL secretion was increased by exposure to ether, a stimulus that acts on the release phase of PRL secretion. In rats in whom the depletion-transformation of PRL was induced by a prior brief period of suckling, subsequent exposure to ether caused a rise in serum PRL levels. The response was completely blocked in rats given VIP antiserum, whereas animals given nonimmune serum showed a significant increase in serum PRL to 38.6 +/- 17.3 ng/ml. We conclude from these studies that VIP mediates the acute PRL response to suckling and is required for maintenance of PRL levels in continuously suckling animals but is not the only factor causing PRL elevation. Complete abolition by the VIP antiserum of the PRL response to ether indicates that the effect of the anesthetic is mediated entirely by the release of VIP. These findings are consistent with the view that VIP is a physiological PRL-releasing factor in the rat.

Vasoactive intestinal peptide: Expression of the prohormone in bacterial cells

A complementary DNA (cDNA) to the messenger RNA for the preprohormone of human vasoactive intestinal peptide (VIP) has been isolated and characterized. This cDNA extends from 65 bases 5′ of the AUG translation start codon through the entire 3′ untranslated region. Using this cDNA we have constructed expression plasmids which allow the synthesis of 120 out of the 150 amino acids of the prohormone in E. coli. This portion of the prohormone gene was either fused to a segment of a bacteriophage structural gene or expressed alone. When expression was induced the fusion protein constituted 15% of the total bacterial cell protein while the prohormone alone was 5%. Both proteins are recognized by antiserum raised against porcine VIP. They provide protein to study the precursor-product relationship of the hormone plus the possibility of identifying cryptic regulatory peptides contained within the prohormone.

Vip binding to epithelial cell membranes of rat ventral prostate: Effect of guanine nucleotides

1. 1.|Specific binding of vasoactive intestinal peptide (VIP) to epithelial cell membranes of rat ventral prostate was reversible, saturable and dependent on time and temperature. 2. 2.|The data suggested the presence of two classes of VIP receptors: a class with high affinity ( K d = 1.7 nM) and low binding capacity (0.5 pmol VIP/mg protein), and another class with low affinity ( K d = 36.2 nM) and high binding capacity (7.5 pmol VIP/mg protein). 3. 3.|Chicken VIP and porcine secretin recognized VIP receptors but exhibited a 10-fold higher and a 40-fold lower affinity than porcine VIP, respectively. However, glucagon, somatostatin, Met-enkephalin and cholecystokinin were ineffective. 4. 4.|GTP inhibited markedly the interaction of VIP with membranes by increasing the rate of dissociation of peptide bound to its receptors. GDP and Gpp(NH)p behaved as GTP but other purine nucleotides and nucleosides did not show any effect.

The isolation and sequence analysis of vasoactive intestinal peptide from a ganglioneuroblastoma.

A ganglioneuroblastoma was excised at surgery from a 1-yr-old girl with severe watery diarrhea. The tumor, weighing 1 g, was extracted in trifluoracetic acid and contained 8.3 nmol immunoreactive vasoactive intestinal peptide. The peptide was isolated by affinity chromatography and high pressure liquid chromatography and was found to be identical to porcine vasoactive intestinal peptide by amino acid analysis and microsequence analysis.

Effects of vasoactive intestinal peptide on canine prostatic contraction and secretion.

Vasoactive intestinal peptide (VIP)-like immunoreactivity was found in intrinsic autonomic ganglion cells and nerve fibers located at the surface and within the canine prostate. In anesthetized dogs, porcine VIP (100-3,000 ng/kg iv) decreased arterial pressure and increased heart rate but did not result in the release of fluid from the prostate, indicating that VIP neither contracted glandular smooth muscle to expel fluid nor provoked secretion. Intravenous infusions of VIP at 10, 50, 100, and/or 200 ng X kg-1 X min-1 produced dose-related decreases in arterial pressure, increases in heart rate, and potentiation of the secretory response to the intravenous administration of pilocarpine and to electrical stimulation of the hypogastric nerves at 2 but not at 20 Hz. VIP at 1 microgram/ml neither contracted isolated strips of prostate nor modified their contraction by norepinephrine. It is unlikely that VIP mediates hypogastric nerve-induced prostatic contraction or secretion in the dog, but VIP may serve as a neuromodulator of nerve-induced secretion.

Self‐association and solubility of peptides.

Self‐associated species of the protected C‐terminal tetrapeptide segment of porcine vasoactive intestinal peptide and related short sequences in methylene chloride have been disrupted by adding increasing amounts of dimethylsulphoxide. This structural transition has been monitored following the disappearance of the amide I carbonyl stretching band assigned to strongly intermolecularly hydrogen‐bonded molecules (1655–1633 cm‐1) in the infrared absorption spectra. A scale for the propensity of the various peptides to aggregate has been established. Substitution of the asparagine residue by a β‐tert.‐butylaspartic acid residue in the tripeptide drastically reduces the extent of self‐association. The increasing tendency to aggregate shown by these peptides is paralleled by a decrease in their solubility. The impact of these results on the strategy of synthesis of porcine vasoactive intestinal peptide is briefly outlined.

Vasoactive intestinal peptide in cerebrospinal fluid

Immunoreactive vasoactive intestinal peptide (VIP) was measured in lumbar and ventricular cerebrospinal fluid (CSF) from patients with various neurological disorders and in 2 hour aliquots of cisternal fluid removed continuously from rhesus monkeys. Although most of the VIP in concentrated pools of human ventricular fluid and of monkey cisternal fluid co-eluted with synthetic porcine VIP 28 on a column of Sephadex G-25 superfine, there was evidence that smaller immunoreactive fragments were also present. A circadian pattern of CSF VIP concentration was observed in 2 of the 3 monkeys studied, with highest levels occurring at night and lowest during the day. Ventricular fluid VIP levels were highest in hydrocephalic children and lowest in patients with multiple sclerosis or epilepsy, while VIP was not detectable in ventricular fluid from patients in coma following a severe head injury. There were no significant differences in VIP concentrations in CSF from patients with dystonia, Parkinson's disease, or Alzheimer's disease, suggesting that VIP containing neurons are not affected in these disorders. Lumbar fluid VIP levels were low in patients undergoing aneurysm surgery. Since VIP is a potent vasodilator, these findings may have important implications in relation to the development of vasospasm following subarachnoid hemorrhage.

Receptors for vasoactive intestinal peptide on isolated epithelial cells of rat ventral prostate

Receptors for porcine vasoactive intestinal peptide have been characterized in isolated epithelial cells of rat ventral prostate. The interaction of 125I-labelled VIP with cells was rapid, reversible, specific, saturable and dependent on temperature. Degradation of peptide and receptors was minimized at 15°C. At apparent equilibrium, the binding of 125I-labelled peptide was competitively inhibited by native VIP in the 1·10 −10−10 −7 M range concentration. The binding data were compatible with the existence of two classes of receptors: a high-affinity class with a K d = 4.0 nM and a low binding capacity (0.12 pmol VIP/mg cell protein), and a low-affinity class with a K d = 17.8 nM and a high binding capacity (1.6 pmol VIP/mg cell protein). Chicken VIP and porcine secretin exhibited a 7-fold higher and a 7-fold lower affinity than porcine VIP for binding sites, respectively. Glucagon, Leu-enkephalin, Met-enkephalin and somatostatin were ineffective. The presence of high-affinity receptors for VIP together with previous reports on the occurrence of VIP-containing neurones innervating the male genitourinary tract strongly suggest that this peptide may be important in the physiological regulation of the functions of prostatic epithelium.

Cyclic AMP-stimulating effect of vasoactive intestinal peptide in isolated epithelial cells of rat ventral prostate

Vasoactive intestinal peptide (VIP) has been shown to increase cyclic AMP content in isolated epithelial cells of rat ventral prostate. The stimulatory effect of VIP was dependent on time and temperature and was potentiated by a phosphodiesterase inhibitor. At 15°C, the response occurred in the 1·10 −10−10 −7 M range of VIP concentrations. Half-maximal stimulation of cellular cyclic AMP was obtained at 1.4 nM and maximal stimulation (3-fold basal level) at about 100 nM VIP. Chicken VIP and porcine secretin were agonists of porcine VIP but exhibited a 2-times higher and a 170-times lower potency, respectively. A high concentration (1·10 −6 M) of glucagon, somatostatin, neurotensin, substance P, Met-enkephalin or Leu-enkephalin did not modify cAMP levels. The finding of a VIP-stimulated cAMP system in rat prostatic epithelial cells together with the previous characterization of high-affinity receptors for VIP in the same cell preparation, as well as the presence of VIP-containing neurones innervating the male genitourinary tract, strongly suggest that VIP may be involved in prostatic growth regulation and function.

Co-localization of vasoactive intestinal peptide (VIP) and enkephalins in chromaffin cells of the adrenal gland of amphibia. Stimulation of corticosteroid production by VIP

Recent studies have shown that biologically active peptides and monoaminergic neurotransmitters coexist in certain neuronal cell populations. Using the immunofluorescence technique, we have examined the localization of enkephalins, vasoactive intestinal peptide (VIP) and tyrosine hydroxylase in the adrenal gland of the frog Rana ridibunda . Most chromaffin cells which stained for tyrosine hydroxylase contained VIP-like immunoreactivity, whereas methionine- (Met-) and leucine- (Leu-) enkephalin-like immunoreactivity was detected in about 40% of the cells revealed by the anti-tyrosine hydroxylase serum. No VIP- or enkephalin-like immunoreactive nerve fibres were observed. Since in the frog, the chromaffin cells are in close contact with the adrenocortical (interrenal) tissue, a possible action of VIP and opiates on corticosteroidogenesis has been investigated. At doses 10 −6 and 10 −5M, 20-min infusions of synthetic porcine or chicken VIP elicited a significant increase in corticosterone and aldosterone production by perifused frog adrenals, in a dose-dependent manner. As compared to ACTH, VIP was several orders of magnitude less effective in stimulating corticosteroid production. Morphine, Met- and Leu-enkephalins (10 −5M) had no effect on spontaneous secretion of corticosteroids. In addition, Met- and Leu-enkephalins (10 −5M) did not alter the production of corticosterone induced by ACTH. These results suggest that VIP contained in the chromaffin cells of the frog adrenal gland may exert a local action in stimulating corticosteroid production by the interrenal tissue.

Effect of Vasoactive Intestinal Peptide on Gastric Secretion in the Cat

The effects of porcine vasoactive intestinal peptide on the acid and pepsin secretions from denervated gastric pouches and innervated stomach were studied in conscious cats both in basal conditions and after stimulation with pentagastrin, histamine, or a liver meal. In contrast with the well-known inhibitory effect of vasoactive intestinal peptide on acid and pepsin secretions in dogs, the peptide induced in cats an increase of the acid and pepsin responses to pentagastrin and an increase of the gastric mucosal blood flow as determined by aminopyrine clearance. Vasoactive intestinal peptide similarly enhanced the acid and pepsin responses to a liver meal in spite of a significant inhibition of the postprandial release of gastrin. The peptide increased the pepsin response but slightly decreased the acid response to histamine. Thus in cats, porcine vasoactive intestinal peptide consistently stimulates pepsin secretion and potentiates the meal- and pentagastrin-induced acid responses.

A new solid-phase synthesis of porcine vasoactive intestinal peptide using Nα-9-fluorenylmethyloxycarbonyl amino acids

The solid-phase synthesis of an octacosapeptide amide corresponding to the amino acid sequence of porcine vasoactive intestinal peptide (VIP) is described. No final treatment with strong, anhydrous acid was employed, since the use of base-labile 9-fluorenylmethyloxycarbonyl amino acids bearing tert-butyl based side chain protection enabled the peptide chain assembly to be performed on p-benzyloxybenzyl amine resin, which was cleaved from the whole peptide amide at the end of the synthesis by diluted trifluoroacetic acid.

Synthesis, biological and immunochemical properties of analogues of secretin and vasoactive intestinal peptide (VIP): The vasectrins

Three analogues of porcine secretin were synthesized with altered amino acid residues present in positions corresponding to those in porcine vasoactive intestinal peptide (VIP). We call these analogues vasectrins (VS). Problems in the syntheses of secretin and VIP are discussed. The biological and immunochemical behaviour of the analogues was studied. This allowed some conclusions about structure-activity relationships in the secretin/VIP family.

Characterization of vasoactive intestinal peptide receptors in human colonic epithelial cells.

Receptors, i.e. specific binding sites for vasoactive intestinal peptide (VIP), have been characterized in human colonic epithelial cells isolated by EDTA treatment using 125I-labeled porcine VIP. The binding was time and temperature dependent. Conditions of apparent equilibrium were obtained at 15 C after 45 min of incubation in the presence of 2.1-7.4 micrograms cell DNA-ml; these conditions minimized the degradation of the peptide and the binding sites. Native VIP competitively inhibited the binding of [125I]VIP in the range of 3 x 10(-11)-10(-7) M, and half-maximal inhibition was observed at 2 x 10(-9) M VIP. Scatchard analysis of these data was consistent with the existence of two classes of binding sites: 7.8 x 10(-9) high affinity sites/microgram DNA with a dissociation constant (Kd) of 1.4 x 10(-9) M, and 12.0 x 10(10) low affinity sites/microgram DNA with a Kd of 46 x 10(-9) M. Among the natural hormones structurally related to VIP, gastric inhibitory polypeptide (GIP) and glucagon had no effect on the binding of labeled porcine VIP. Porcine secretin inhibited [125I]VIP binding, but at doses 1000 times higher than those of porcine VIP. Studies of the coupling between the binding of VIP and the stimulation of cAMP formation indicated a nonlinear relationship between the two processes, with full activation of the cAMP-producing system with occupancy of only a limited number of the binding sites. The presence of binding sites with high affinity for VIP coupled with the cAMP production in human colonic epithelial cells support the concept that this peptide may contribute to the physiological regulation of the functions of the human colonic epithelium in normal and pathological conditions.

Effects of vasoactive intestinal peptide and pancreatic polypeptide in rabbit intestine.

The effects of porcine vasoactive intestinal peptide (VIP) and bovine pancreatic polypeptide (PP) on jejunal, ileal, and colonic fluid transport were studied in the rabbit. VIP produced secretion in the small intestine (jejunum greater than ileum) but did not affect absorption in the colon. PP had no secretory effects in jejunum, ileum, or colon. The small intestinal secretion induced by VIP was not associated with raised cAMP concentrations in the mucosa; this suggests that the secretory effects of VIP in vivo are mediated by a mechanism other than stimulation of adenylate cyclase.

Quantitative studies of vasoactive intestinal peptide (VIP) binding sites and VIP-induced adenosine 3':5'-monophosphate production in epithelial cells from duodenum, jejunum, ileum, cecum, colon and rectum in the rat.

The binding of vasoactive intestinal peptide (VIP) and its effect on adenosine 3':5'-monophosphate (cyclic AMP) production were measured in isolated rat intestinal epithelial cells from duodenum, jejunum ileum, cecum, colon and rectum. In every segment tested, VIP binding and VIP-induced cyclic AMP production exhibited a similar pattern with two populations of VIP binding sites and similar magnitude of cyclic AMP production. Continuous displacement of the binding of 125I-labelled VIP and stimulation of cyclic AMP production were observed in the range of 10(-10)--10(-7) M VIP concentrations. Fifty per cent inhibition of the initial binding of tracer was obtained with 2.2 to 3.2 nM VIP. The Km of stimulation of cyclic AMP production was 1.2 to 2.6 nM VIP. Chicken VIP and porcine secretin showed a 4-fold higher and a 100-fold lower affinity than porcine VIP for binding sites, respectively. The same was true for the stimulation of cyclic AMP production. The existence of receptors highly sensitive to VIP in the separate segments of the bowel corresponds to the presence of high concentration of VIP at the vicinity of epithelial cells and strongly suggests that VIP is active in regulating different intestinal functions.