Vasoactive intestinal peptide stimulates rat adrenal glucocorticoid secretion, through an ACTH receptor-dependent activation of the adenylate cyclase signaling pathway

Vasoactive intestinal peptide (VIP) concentration-dependently enhanced corticosterone and cyclic-AMP release by dispersed rat inner adrenocortical cells. A VIP-receptor antagonist and the ACTH-receptor antagonist corticotropin-inhibiting peptide annulled both adrenocortical-cell responses to VIP, while the protein kinase (PKA) inhibitor H-89 blocked only corticosterone response. Collectively, these findings suggest that VIP stimulates glucocorticoid secretion of rat adrenals, through the aspecific activation of ACTH receptors coupled with the adenylate cyclase/PKA-dependent signaling pathway.     

Vasoactive intestinal peptide stimulation of human trabecular meshwork cell growth

PURPOSE: To demonstrate that vasoactive intestinal peptide (VIP), a 28-amino acid neuropeptide, is a growth factor of human trabecular meshwork (TM) cells in culture and in a corneoscleral explant organ culture treated with laser trabeculoplasty (LTP). METHODS: Proliferating human TM cells in cell cultures were incubated with VIP for 20 hours, followed by total cell number determination, using a Coulter counter. The percentage of proliferating TM cells was assessed, using an antibody against the proliferating cell nuclear antigen (PCNA). To test the growth effect of VIP on TM cells in situ, corneoscleral explants in organ cultures were first treated with argon LTP to initiate TM-cell proliferation and then were exposed to VIP for 48 hours. The mitotic TM cells were demonstrated immunocytochemically, using anti-PCNA in paraffin sections of the explants; and the total number of TM cells was determined after paraffin sections were counterstained by hematoxylin. RESULTS: Vasoactive intestinal peptide dose-dependently stimulated the proliferation of TM cells in cell culture. Treatment with 5 x 10(-10) M VIP resulted in a maximal increase of 40% in cell number. The effect of VIP was blocked by a VIP antagonist. The number of PCNA-stained TM cells and the total cell number in the TM in LTP-treated corneoscleral explants were increased by VIP. CONCLUSIONS: Exogenously applied VIP stimulated the proliferation of human TM cells in subconfluent cultures and in LTP-treated corneoscleral explants. In that LTP has been shown to increase the number of TM cells in situ, the growth stimulatory effect of VIP may help enhance this therapy.     

Vasoactive intestinal peptide and epidermal growth factor: co-mitogens or inhibitors of keratinocyte proliferation in vitro?

Adenosine myocardial perfusion single-photon emission computed tomography (SPECT) is now increasingly used for risk stratification of patients with known or suspected coronary artery disease. However, the incremental prognostic value of this test over clinical and historical information in a large series of women has not been examined. Thus, we studied 923 consecutive women who underwent adenosine technetium (Tc)-99m sestamibi myocardial perfusion SPECT and were followed-up for a mean period of 26+/-8 months. During the follow-up period, 77 hard events (46 cardiac deaths and 31 nonfatal myocardial infarctions) occurred. The results of the perfusion scan significantly risk stratified the population; patients with normal scans had a low rate of nonfatal myocardial infarction and cardiac death (< 1%/year of follow up). Patients with mildly abnormal scans had low cardiac death rates (0.9%/year of follow up); these rates increased as a function of scan abnormality (4.1% and 7.5% mortality per year of follow up in moderate and severely abnormal scans). Cox proportional hazards analysis demonstrated that after adjusting for prior myocardial infarction and diabetes mellitus (the most predictive individual clinical variables [global chi-square=22.5, p <0.001]), as well as heart rate at rest (the most predictive physiologic variable [chi-square=3.8; p=0.05]), the most predictive nuclear variable (summed stress score [chi-square=48.5; p <0.0001]) added significant incremental prognostic information (global chi-square increased from 22.5 to 56.2 [p <0.0001]). In conclusion, adenosine myocardial perfusion SPECT added significant incremental prognostic information to clinical and physiologic variables in women. Normal scans were associated with an excellent prognosis. In contrast, patients with moderately to severely abnormal scans were at a higher risk for future cardiac events.     

Vasoactive intestinal peptide and somatostatin receptor scintigraphy for differential diagnosis of hepatic carcinoid metastasis

We report a case of a hepatic carcinoid metastasis mimicking a hemangioma on ultrasound and on CT. Indium-111-DTPA-D-Phe-1-octreotide (111In-OCT) and 123I-vasoactive intestinal peptide (123I-VIP) receptor images suggested a carcinoid metastasis of the liver. The final diagnosis was established histopathologically. The differential diagnosis of liver lesions is discussed.     

Vasoactive intestinal peptide, but not pituitary adenylate cyclase-activating peptide, modulates the responsiveness of the gonadotroph to LHRH in man

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP) are hypothalamic peptides sharing considerable sequence homology which are postulated to be hypophysiotrophic releasing factors. When infused into man, PACAP has no effect on anterior pituitary hormone levels, while VIP causes a significant increase in circulating prolactin concentrations. However, PACAP has recently been shown to augment the release of LH and FSH in response to LHRH in rat anterior pituitary cell culture. In order to ascertain if either peptide has a similar effect in man, PACAP and VIP were infused at 3.6 pmol/kg per min into six healthy male volunteers, and an LHRH test was performed 30 min after the infusion was commenced. Infusion of PACAP did not alter the gonadotrophin response to LHRH significantly. However, VIP augmented the release of LH significantly, both during the infusion and for 30 min thereafter, although there was no effect on FSH release. Thus VIP, but not PACAP, potentiates the release of LH after LHRH injection in man.     

Control of human luteal steroidogenesis: role of growth hormone-releasing hormone, vasoactive intestinal peptide, and pituitary adenylate cyclase-activating peptide

OBJECTIVE: To examine the possible effect of growth hormone-releasing hormone (GHRH), vasoactive intestinal peptide, and pituitary adenylate cyclase-activating peptide on basal and hCG-stimulated P production by human luteal cells. DESIGN: Cultures of human luteal cells from the early and midluteal phase. SETTING: All corpora lutea were obtained from the Obstetrics and Gynecology Department of the Università Cattolica, a public care center. PATIENT(S): Ten nonpregnant women between 35 and 47 years of age underwent surgery for various nonendocrine disorders, such as leiomyomatosis. INTERVENTION(S): Corpora lutea were obtained at the time of hysterectomy. MAIN OUTCOME MEASURE(S): Luteal cells were incubated with GHRH, vasoactive intestinal peptide, and pituitary adenylate cyclase-activating peptide with or without hCG at different concentrations. RESULT(S): Pituitary adenylate cyclase-activating peptide stimulated P production in a dose- and time-dependent manner, whereas GHRH and vasoactive intestinal peptide did not affect luteal steroidogenesis. None of the three peptides were found to synergize with hCG. CONCLUSION(S): Pituitary adenylate cyclase-activating peptide can influence human luteal steroidogenesis.     

The rat dermorphin-like immunoreactivity is supported by an aminopeptidase resistant peptide

Site-directed antibodies against synthetic related dermorphin peptides were previously produced and characterized. One of them, which specifically recognizes the crucial 'opioid message' (the N-terminal part of the dermorphin molecule (i.e. Tyr-D-Ala-Phe-Gly) was selected in order to detect and locate endogenous dermorphin-like molecules in rat, mouse and guinea pig tissues. Dermorphin-like peptides were found to be present in tissues known to contain peptides such as neurons in the central nervous system, nerve fibers in the gut and B and T immune cells. With all the tissues assayed, the HPLC profile obtained on the immunoreactive material showed the same main peak eluted at a retention time of 32 +/- 1 min. The results of biochemical experiments in which enzymatic treatments were performed on the dermorphin-like immunoreactivity indicate the immunoreactivity is a peptide resistant to aminopeptidase hydrolysis. This finding suggests the presence of a residue conferring resistance to proteolytic processes of this kind, which is likely to be a D-amino acid residue.     

K+ is an endothelium-derived hyperpolarizing factor in rat arteries

In arteries, muscarinic agonists such as acetylcholine release an unidentified, endothelium-derived hyperpolarizing factor (EDHF) which is neither prostacyclin nor nitric oxide. Here we show that EDHF-induced hyperpolarization of smooth muscle and relaxation of small resistance arteries are inhibited by ouabain plus Ba2+; ouabain is a blocker of Na+/K+ ATPase and Ba2+ blocks inwardly rectifying K+ channels. Small increases in the amount of extracellular K+ mimic these effects of EDHF in a ouabain- and Ba2+-sensitive, but endothelium-independent, manner. Acetylcholine hyperpolarizes endothelial cells and increases the K+ concentration in the myoendothelial space; these effects are abolished by charbdotoxin plus apamin. Hyperpolarization of smooth muscle by EDHF is also abolished by this toxin combination, but these toxins do not affect the hyperpolarizaiton of smooth muscle by added K+. These data show that EDHF is K+ that effluxes through charybdotoxin- and apamin-sensitive K+ channels on endothelial cells. The resulting increase in myoendothelial K+ concentration hyperpolarizes and relaxes adjacent smooth-muscle cells by activating Ba2+-sensitive K+ channels and Na+/K+ ATPase. These results show that fluctuations in K+ levels originating within the blood vessel itself are important in regulating mammalian blood pressure and flow.     

Vasoactive intestinal polypeptide (VIP) innervation of rat spleen, thymus, and lymph nodes

In the thymus, VIP-positive (+) fibers were found in the capsular/septal system, cortex, and medulla. In the spleen, VIP+ nerves coursed along large arteries and central arterioles, and in the white pulp, venous/trabecular system, and red pulp. Splenic VIP innervation was more robust in Long-Evans hooded rats than in Fischer 344 rats. VIP+ nerves in mesenteric lymph nodes were found in the cortex, and along the cortical vasculature and medullary cords. No VIP innervation was observed in popliteal lymph nodes. Immunocytes also were VIP+, suggesting that both neural and cellular synthesis of VIP contributes to VIP concentration in lymphoid organs. Surgical sympathectomy did not alter splenic or thymic VIP content, respectively, and VIP innervation of these organs was not altered, suggesting an origin for VIP+ nerves other than the sympathetic nervous system.     

Distribution of cells expressing vasoactive intestinal peptide/peptide histidine isoleucine-amide precursor messenger RNA in the rat brain

The distribution of cells expressing vasoactive intestinal peptide/peptide histidine isoleucine-amide precursor messenger RNA was investigated in the rat brain and pituitary by in situ hybridization using a synthetic 35S-labeled oligonucleotide probe. Detection of labeled neurons by light-microscopic radioautography revealed a selective repartition of the messenger RNA-expressing cells. Several major vasoactive intestinal peptide/peptide histidine isoleucine-amide messenger RNA-containing cell groups were demonstrated including layers II-VI of the cerebral cortex, the suprachiasmatic nucleus and various thalamic structures such as the ventrolateral, posterior, lateral reticular, paracentralis and gelatinosus nuclei. Positive cells, to a lesser extent, were also found in the limbic system, medial preoptic area, superior and inferior colliculi as well as in the central gray matter. They were totally absent in the pituitary and the pineal gland of normal rats. The results of the present study provide a detailed mapping of neurons expressing vasoactive intestinal peptide/peptide histidine isoleucine-amide messenger RNA in the adult rat brain. The predominance of vasoactive intestinal peptide/peptide histidine isoleucine-amide messenger RNA-containing neurons in the cerebral cortex, suprachiasmatic nucleus and thalamus suggest that vasoactive intestinal peptide is mainly involved in the control of cortical informations, circadian rhythms and sensory perception in agreement with several physiological data.     

Biosynthesis of growth hormone-releasing factor by fetal rat cerebrocortical and hypothalamic cells

The biosynthesis of growth hormone-releasing factor (GRF) by cerebrocortical tissue is controversial. Although several reports have indicated its presence in certain rat cortical areas and in cultured rat hypothalamic cells, no data exist demonstrating its biosynthesis in these areas. In this study, we have investigated the capacity of fetal rat cerebrocortical and hypothalamic cells in culture for synthesizing GRF. Fetal cerebrocortical and hypothalamic cells were exposed to [3H]Arg for 48 h. Medium and cell extracts were processed and [3H]Arg-IR-rGRF was isolated by affinity chromatography and characterized by HPLC. Intracellular [3H]Arg-IR-rGRF from both hypothalamic and cerebrocortical cells exhibited four major peaks, one of them coeluting with synthetic rGRF. In cerebrocortical cultures, newly synthesized and released [3H]Arg-IR-rGRF showed a similar pattern to the cell content. However, in media from hypothalamic cells, higher hydrophobicity molecular forms were absent. The data demonstrated that fetal cerebrocortical and hypothalamic cells in primary culture synthesize GRF with similar posttranslational processing, but with different molecular patterns of secretion.     

Is reperfusion injury an important cause of mucosal damage after porcine intestinal ischemia?

BACKGROUND: Intestinal ischemic injury is exacerbated by reperfusion in rodent and feline models because of xanthine oxidase-initiated reactive oxygen metabolite formation and neutrophil infiltration. Studies were conducted to determine the relevance of reperfusion injury in the juvenile pig, whose low levels of xanthine oxidase are similar to those of the human being. METHODS: Ischemia was induced by means of complete mesenteric arterial occlusion, volvulus, or hemorrhagic shock. Injury was assessed by means of histologic examination and measurement of lipid peroxidation. In addition, myeloperoxidase, as a marker of neutrophil infiltration, and xanthine oxidase-xanthine dehydrogenase were measured. RESULTS: Significant ischemic injury was evident after 0.5 to 3 hours of complete mesenteric occlusion or 2 hours of shock or volvulus. In none of these models was the ischemic injury worsened by reperfusion. To maximize superoxide production, pigs were ventilated on 100% O2, but only limited reperfusion injury (1.2-fold increase in histologic grade) was noted. Xanthine oxidase-xanthine dehydrogenase levels were negligible (0.4 +/- 0.4 mU/gm). CONCLUSIONS: Reperfusion injury may not play an important role in intestinal injury under conditions of complete mesenteric ischemia and low-flow states in the pig. This may result from low xanthine oxidase-xanthine dehydrogenase levels, which are similar to those found in the human being.     

Lack of effect of three putative vasoactive intestinal peptide receptor antagonists on vasoactive intestinal peptide-induced secretory responses in rat colon

A simple, rapid and efficient method for the preparation of a potential brain blood-flow agent, N-[11C-methyl]-chlorphentermine ([11C]NMCP), is described. Optimization of the radiochemical yield of [11C]NMCP was accomplished by a Gabriel-like reaction which permits the transformation of a primary amine to a secondary amine through a sequence of acylation, deprotonation, monomethylation and saponification. This method precludes the formation of polymethylated by-products which can reduce radiochemical yields, particularly with low specific activity 11CO2.