Cosecretion of peptide histidine methionine (PHM) and vasoactive intestinal peptide (VIP) in patients with VIP-producing tumors

The relative importance of vasoactive intestinal peptide and peptide histidine isoleucine as physiological regulators of prolactin in the domestic turkey

In mammals, prolactin (PRL) secretion is regulated by vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI). In birds, however, VIP is considered a PRL-releasing factor (PRF), while the role of PHI is unknown. The purpose of this study was to compare the effects of turkey PHI (tPHI) and turkey VIP (tVIP) on PRL secretion in vitro, and to study their physiological significance in vivo through active immunization against tPHI and tVIP. In vitro studies were conducted using pituitary cell cultures from female turkeys. In the in vivo study, female turkeys were immunized with keyhole limpet hemocyanin (KLH; control), synthetic tPHI conjugate (KLH-tPHI), or synthetic tVIP conjugate (KLH-tVIP). Both tVIP and tPHI stimulated PRL secretion from anterior pituitary cells in a dose response manner. However, tPHI was 100-fold less potent than tVIP in stimulating maximum PRL secretion in vitro. In addition, the highest dose (10(-4) M) of tPHI inhibited its own PRL-releasing activity as well as that of VIP-stimulated PRL release. Whereas, circulating PRL levels and nesting activity remained low and unchanged during the photo-induced reproductive cycle (i.e., experimental period) in tVIP-immunized birds, control and tPHI-immunized turkeys showed a significant increase in plasma PRL levels and in the incidence of incubation behavior over time following photostimulation. These findings, taken together with earlier results, indicate that VIP is the sole physiological PRF in the turkey (avian species).

Gastroenteropancreatic tumours and prohormones

The structures and post-translational maturation of pancreatic and gastrointestinal prohormones are reviewed with emphasis on Danish contributions to today's knowledge. The review describes general, cell-specific, and tumour-specific prohormone-processing patterns. Since prohormone-processing in endocrine tumours is often attenuated, conventional assays that measure only the phenotypic endpoint of hormone gene expression (i.e. the bioactive hormone) do not quantitate tumour activity accurately. In contrast, measurements that include also prohormones and processing intermediates provide more accurate data on hormone synthesis in gastroenteropancreatic endocrine tumours. In order to comply with such demands we have developed a new analytical principle (processing-independent analysis (PIA)) which quantitates the entire translation product irrespective of the degree of processing. The significance of PIA in routine diagnostics awaits prospective evaluation. We hope that the present review illustrates how the tumour biology of endocrine cells in the pancreas and the gut has been an essential research area in Danish gastroenterology and endocrinology--one purpose being improvement of early diagnosis of endocrine tumours in the gut and the pancreas.

Effect of thyroid hormones on vasoactive intestinal polypeptide gene expression in the rat cerebral cortex and anterior pituitary

We report here data on the expression of the various sequences derived from the prepro-vasoactive intestinal polypeptide (VIP) precursor and VIP mRNA in the anterior pituitary gland and cerebral cortex of hypothyroid and hyperthyroid rats. Using specific antisera to each of the prepro-VIP sequences we demonstrated an increase of all prepro-VIP derived sequences, and accordingly, found that the number of cells expressing each of these sequences were markedly augmented in the anterior pituitary of the hypothyroid rats. This was accompanied by a marked increase in VIP mRNA. In the cerebral cortex of the hypothyroid rats no changes were observed. In the pituitary of hyperthyroid animals a significant decrease was seen for prepro-VIP 22-79, VIP and prepro-VIP 156-170, whereas in the cerebral cortex a significant increase was observed for prepro-VIP 22-79, PHI and VIP. We were not able to demonstrate any changes in VIP mRNA in the cerebral cortex or pituitary of the hyperthyroid rats. Gel permeation chromatography and reverse-phase HPLC of extracts from cerebral cortex showed elution profiles identical to the synthetic counterparts. The reported data provide further evidence of a tissue-specific expression and regulation of the VIP gene products.

All prepro-VIP-derived peptides, except PHI/PHV, are expressed in the female rat anterior pituitary and increased by estrogen

The expression of VIP precursor products: prepro-VIP(22-79), peptide histidine isoleucine (PHI), peptide histidine valine (PHV), prepro-VIP(111-122), VIP, prepro-VIP(156-170), and prepro-VIP mRNA in the anterior pituitary of estrogen-treated, ovariectomized rats, of ovariectomized controls, and of sham-operated controls was examined. Using radioimmunoassays based on antisera against each of the prepro-VIP sequences, we found that all sequences were expressed and markedly induced by estrogen, except PHI and PHV, which both were undetectable. By immunohistochemistry, it appeared that the number of cells immunoreactive for each of these sequences was increased in the estrogen-treated animals. However, PHI/PHV-immunoreactive cells could not be detected, despite the use of four different PHI antisera with different specificities. Estrogen treatment increased the prepro-VIP mRNA as judged by Northern blotting. In situ hybridization signals for both VIP mRNA and PHI mRNA were observed in few pituitary cells from control animals whereas strong positive signals were observed in a larger number of cells after estrogen treatment. The findings show that estrogen causes activation of the VIP gene expression in anterior pituitary cells, and that the absence of PHI and PHV probably is due to translational or posttranslational events.

Peptide histidine valine (PHV) is present and biologically active in the human female genital tract

The occurrence of vasoactive intestinal polypeptide (VIP), peptide histidine methionine (PHM) and peptide histidine valine (PHV) in the human female genital tract was studied by means of radioimmunoassay in combination with gel chromatography. In addition, the effect of PHV on genital smooth muscle activity was investigated in vitro and compared to that of VIP. Immunoreactive VIP, PHM and PHV were present in all regions of the human female genital tract, the highest concentrations being measured in the vagina and the uterine cervix. The peptides displayed similar regional distribution and as expected from the structure of the VIP precursor molecule in which the examined peptides are contained, the molar ratio of VIP to the total PHM/PHV immunoreactivity was close to 1:1. In all regions PHV constituted 50-70% of the total PHM/PHV immunoreactivity indicating that the dibasic conversion site after PHM was uncleaved. VIP and PHV were found to be equipotent relaxants of the smooth muscle from the Fallopian tube and the myometrium. The present study indicates that PHV like PHM and VIP may act as a neurotransmitter in the human female genital tract and thus participate in the local nervous control of the reproductive functions.

Vasoactive intestinal polypeptide (VIP) and peptide histidine methionine (PHM) in human penile corpus cavernosum tissue and circumflex veins: localization and in vitro effects

Localization and functional effects of vasoactive intestinal polypeptide (VIP) and peptide histidine methionine (PHM), two peptides derived from a common precursor molecule, were investigated in isolated preparations from human penile corpus cavernosum (CC) and circumflex vein (CV). VIP- and PHM-immunoreactivity (IR) was demonstrated in both CC and CV. The concentrations of VIP-IR and PHM-IR in CC tissue were 54.4 +/- 15.3, and 42.0 +/- 7.5 pmol g-1 wet weight respectively with a VIP/PHM ratio of 1.5 +/- 0.4 (mean +/- SEM). The corresponding values for CV tissues were 28.0 +/- 7.7 and 9.6 +/- 2.6 pmol g-1 wet weight with a VIP/PHM ratio of 3.1 +/- 0.4. CC and CV displayed VIP- and PHM-IR confined to nerve fibres in close relation to bundles of smooth muscle cells and blood vessels in both tissues. In vitro, VIP and PHM had no effects in unstimulated tissue preparations. Both peptides concentration-dependently (10(-9)-10(-6) M) relaxed CC and CV preparations precontracted with 3 x 10(-6) M noradrenaline. In CC the maximum relaxant effect of VIP and PHM was 22 +/- 11% and 9 +/- 9% and in CV the corresponding values were 82 +/- 8% and 93 +/- 3% respectively. The present study supports the hypothesis of VIP and PHM as neurotransmitters and/or neuromodulators in the nervous control of penile erection.

Expression of preproVIP-derived peptides in the human gastrointestinal tract: a biochemical and immunocytochemical study

In order to study biosynthetic processing of the precursor for vasoactive intestinal peptide (preproVIP) in the human gut we have developed antisera against the five functional domains of the precursor molecule: preproVIP 22-79, peptide histidine methionine (PHM), preproVIP 111-122, VIP and preproVIP 156-170. The antisera were used to quantify and characterize VIP-precursor peptides by radioimmunoassay (RIA) together with high-pressure liquid Uchromatography (HPLC) and to examine their cellular localization and colocalization by immunocytochemistry. All five peptides were expressed but not in equimolar amounts as expected from the amino acid sequence of the precursor. However, the ratios between them were fairly constant throughout the gastrointestinal tract. The only exceptions were the lower concentrations of PHM and preproVIP 111-122 in the gastric antrum which could be explained by the presence of PHV (the C-terminally extended form of PHM which includes preproVIP 111-122) in large concentrations in this region. It was also found that the C-terminal lysine residue of preproVIP is not removed during processing. Immunocytochemically all preproVIP-derived peptides were shown in neuronal elements. They had a similar distribution throughout the gut suggesting coexistence, a finding which was supported by doublestaining. The findings indicate that differences in the posttranslational processing of preproVIP exist in subpopulations of neurons in the human gut.

PreproVIP-derived peptides in tissue and plasma from patients with VIP-producing tumours

To elucidate the biosynthetic processing of the precursor for vasoactive intestinal peptide (prepro-VIP) in tumours producing VIP we have used newly developed radioimmunoassays directed against the five functional domains of the VIP precursor molecule: preproVIP 22-79, peptide histidine methionine (PHM), preproVIP 111-122, VIP and preproVIP 156-170 in combination with HPLC to identify and quantify the peptides in tumour specimen and plasma from patients with the watery diarrhoea syndrome. Elevated quantities of all the five peptides were found in the 13 tumours (nine neurogenic tumours, one pheochromocytoma, three pancreatic carcinomas) examined. The preproVIP derived peptides were expressed in non-equimolar amounts and the relative proportion of the various peptides differed markedly from tumour to tumour. The pheochromocytoma was the only tumour type which contained large amounts of preproVIP 156-170 in comparison with the other peptides. A proportion of the VIP precursor which varied from 7% to 73% followed a pathway in which the dibasic conversion site after PHM was uncleaved as evidenced by the presence of PHV, a C-terminally extended form of PHM. It was also found that unlike normal tissue a fraction of the C-terminal VIP precursor peptide, preproVIP 156-170, was having its C-terminal lysine residue removed during processing. The findings indicate that various post-translational processing pathways of preproVIP exist. All the peptide sequences produced in the tumour tissue were secreted as evidenced by their presence in plasma in elevated concentrations. The plasma levels of preproVIP 22-79, preproVIP 111-122 and PHV exceeded those of the remaining preproVIP-derived peptides suggesting that determination of these peptides in patients with VIP-secreting tumours may be better markers than VIP.

Plasma vasoactive intestinal polypeptide concentration determination in patients with diarrhea

Determination of plasma levels of vasoactive intestinal polypeptide (VIP) has been used for screening patients with chronic diarrhea to identify potential neuroendocrine tumors. This 6-year blinded study from 1981 to 1986 examines the causes of elevated VIP levels in patients. In healthy volunteers ( n = 144), VIP concentrations ranged from 14 to 76 pg/mL (mean +/- SE, 28 +/- 12), whereas in chronic renal failure, 4 of 34 patients or 12% [serum creatinine 4.5 - 9.0 mg/dL (397-795 mumols/L)] had an elevation to greater than 100 pg/mL. No patient with idiopathic hepatic cirrhosis (n = 12) had elevation of serum concentration of this peptide. Among 588 consecutive unselected patients undergoing evaluation for chronic diarrhea (n = 362; 62%) or possible neuroendocrine tumor (n = 214; 36%), 23 patients (3.9%) had concentrations greater than 76 pg/mL. In this group, 5 patients had functioning (VIP, 160-5975 pg/mL) and 5 had nonfunctioning (VIP, 80-120 pg/mL) pancreatic islet cell carcinomas: all 10 patients had hepatic metastases. Other known cases of elevated levels of VIP, ranging from 80 to 340 pg/mL, included other neurogenic tumors (n = 3), small- bowel resection (n = 2), inflammatory bowel disease (n = 2), chronic renal failure (n = 1), and prolonged fasting (n = 1). Patients with diarrhea in which VIP-secreting tumors were identified had plasma vasoactive intestinal peptide concentrations greater than 140 pg/mL. In patients with chronic diarrhea, determination of plasma vasoactive intestinal peptide levels did identify tumors secreting this peptide, but the results from this referral institution did not show identification of these tumors early in their clinical course.

Rat PHI, PHI-GLY and PHV (1-42) stimulate adenylate cyclase in six rat tissue and cell membranes

PHI and the two C-terminally extended forms PHI-GLY and PHV(1-42) coexist in rat tissues. We compared the relative potency and efficacy of these three PHI forms and of VIP to stimulate adenylate cyclase activity and, when feasible, to occupy VIP receptors in six rat tissue and cell membranes. With the exception of lung membranes, all three PHI forms were markedly less potent than VIP but all were systematically as efficacious. PHI-GLY and PHV(1-42) were never more potent than PHI itself and their relative potencies revealed four spectra, depending on the membrane preparation tested: 1) PHI = PHI-GLY = PHV(1-42) in hepatic, pulmonary and pancreatic membranes; 2) PHI greater than PHV(1-42) = PHI-GLY in membranes from circulating lymphocytes; 3) PHI = PHV(1-42) greater than PHI-GLY in membranes from the thymocyte cell line 51E; and 4) PHI greater than PHI-GLY = PHV(1-42) in anterior pituitary membranes. These results indicate that the two naturally observed C-terminal extensions of rat PHI variously affected peptide potency on 6 rat membrane preparations.

VIP- and PHI-immunoreactivity in olfactory centers of the adult cat

The purpose of the study was to determine the morphology and distribution of vasoactive intestinal polypeptide- and peptide histidine isoleucine-immunoreactive (VIP- and PHI-ir) neurons and innervation patterns in the main and accessory olfactory bulb, anterior olfactory nucleus, and piriform cortex of the adult cat. In these centers, VIP- and PHI-immunoreactive material are present in the same neuronal types, respectively, therefore summarized as VIP/PHI-ir neurons. In the main olfactory bulb, the majority of VIP/PHI-ir neurons are localized in the external plexiform layer. These neurons give rise to two or more locally branching axons. They form boutons on mitral and external tufted cell bodies. According to the morphology and location, we have classified these neurons as Van Gehuchten cells. Some VIP/PHI-ir neurons are present in the glomerular layer. They have small somata and give rise to dendrites branching exclusively into glomeruli. We have classified these neurons as periglomerular cells. In the granule cell layer, neurons with long apical dendrites and one locally projecting axon are present. In the accessory olfactory bulb, VIP/PHI-ir neurons are localized in the mixed external/mitral/internal plexiform layer. They represent Van Gehuchten cells. In the anterior olfactory nucleus and piriform cortex, VIP/PHI-ir bipolar basket neurons are present. They are localized mainly in layers II/III. These neurons are characterized by a bipolar dendritic pattern and by locally projecting axons forming basket terminals on large immunonegative cell somata. Because of their common morphological features, we summarize them as the retrobulbar VIP/PHI-ir interneuron population. The PHI-ir neurons display the same morphology as the VIP-ir cells. However, they are significantly lower in number with a ratio of VIP-ir to PHI-ir cells about 2:1 in the main and accessory olfactory bulb and in the anterior olfactory nucleus. By contrast, in the piriform cortex the ratio is about 1:1.

Effects of preprovasoactive intestinal polypeptide-derived peptides on ileal output

Tumors associated with the Verner Morrison syndrome secrete peptide histidine methionine, its C-terminally extended variant peptide histidine valine, and vasoactive intestinal peptide. There is evidence that vasoactive intestinal peptide mediates diarrhea, but recent evidence suggested that peptide histidine methionine and peptide histidine valine may be at least as important. Infusion of vasoactive intestinal peptide, peptide histidine methionine, and peptide histidine valine into patients with ileostomies produced mean plateau plasma levels of 163, 1301, and 2106 pM, respectively, which are within the range seen in the Verner Morrison syndrome. Vasoactive intestinal peptide produced an integrated ileal output of 174 (53) g (mean [SEM]), compared with only 20 (7) g with peptide histidine methionine and 10 (3) g with peptide histidine valine. These results suggest that vasoactive intestinal peptide is substantially more important than peptide histidine methionine or peptide histidine valine in mediating diarrhea in the Verner Morrison syndrome.

Characterization and regional distribution of peptides derived from the vasoactive intestinal peptide precursor in the normal human brain

To study the biosynthetic processing of the precursor for vasoactive intestinal peptide (prepro-VIP) in the human brain, we have developed antisera against the five functional domains of the precursor molecule: prepro-VIP 22-79, peptide histidine methionine (PHM), prepro-VIP 111-122, VIP, and prepro-VIP 156-170. The antisera were used in radioimmunoassays in combination with HPLC to identify and quantify the peptides in regions of the human brain. All five peptides were expressed, but mainly in nonequimolar ratios. In only three regions were the same amounts of VIP and PHM found; in the remaining areas the concentration of PHM was two-thirds that of VIP. The concentrations of prepro-VIP 22-79, prepro-VIP 111-122, and prepro-VIP 156-170 were considerably lower than the corresponding VIP concentrations, and the relative concentration of prepro-VIP 111-122 differed between cortical and subcortical areas. A small proportion of the VIP precursor followed a pathway in which the dibasic conversion site after PHM is not cleaved, as evidenced by the presence of a C-terminally extended form of PHM. Finally, it was found that the C-terminal lysine residue of prepro-VIP is not removed during processing. The findings indicate that differences in the posttranslational processing of prepro-VIP exist in subpopulations of neurons in the human brain.

Early postnatal development of vasoactive intestinal polypeptide- and peptide histidine isoleucine-immunoreactive structures in the cat visual cortex

The early postnatal development of neurons containing vasoactive intestinal polypeptide (VIP) and peptide histidine isoleucine (PHI) has been analyzed in visual areas 17 and 18 of cats aged from postnatal day (P) 0 to adulthood. Neuronal types are established mainly by axonal criteria. Both peptides occur in the same neuronal types and display the same postnatal chronology of appearance. Several cell types are transient, which means that they are present in the cortex only for a limited period of development. According to their chronology of appearance the VIP/PHI-immunoreactive (ir) cell types are grouped into three neuronal populations. The first population comprises six cell types which appear early in postnatal life. The pseudohorsetail cells of layer I possess a vertically descending axon which initially gives rise to recurrent collaterals, then forms a bundle passing layers III to V, and finally, horizontal terminal fibers in layer VI. The neurons differentiate at P 4 and disappear by degeneration around P 30. The neurons with columnar dendritic fields of layers IV/V are characterized by a vertical arrangement of long dendrites ascending or descending parallel to each other, thus forming an up to 600 microns long dendritic column. Their axons always descend and terminate in broad fields in layer VI. The neurons appear at P 7 and are present until P 20. The multipolar neurons of layer VI occur in isolated positions and have broad axonal territories. The neurons differentiate at P 7 and persist into adulthood. Bitufted to multipolar neurons of layers II/III have axons descending as a single fiber to layer VI, where they terminate. The neurons appear at P 12 and persist into adulthood. The four cell types described above issue a vertically oriented fiber architecture in layers II-V and a horizontal terminal plexus in layer VI which is dense during the second, third and fourth week. Concurrent with the disappearance of the two transient types the number of descending axonal bundles and the density of the layer VI plexus is reduced, but the latter is maintained during adulthood by the two persisting cell types. Two further cell types belong to the first population: The transient bipolar cells of layers IV, V, and VI have long dendrites which extend through the entire cortical width. Their axons always descend, leave the gray matter, and apparently terminate in the upper white matter. The neurons differentiate concurrently with the pseudohorsetail cells at P 4, are very frequent during the following weeks, and eventually disappear at P 30.(ABSTRACT TRUNCATED AT 400 WORDS)

Expression of membrane receptors and (proto)oncogenes during the ontogenic development and neoplastic transformation of the intestinal mucosa

The functional relationship between membrane receptors involved in signal transduction and (proto) oncogene expression has been explored during the ontogenic development and differentiation of the intestinal mucosa in man and rat. The present review develops detailed picture of the current understanding of some mechanisms underlying growth and function of normal, immortalized and cancerous intestinal epithelial cells.

Peptide histidine methionine (PHM) increases ileostomy output

The human vasoactive intestinal peptide (VIP) gene also encodes peptides histidine methionine (PHM) which has substantial sequence homology with VIP. Both are present in nerve fibers in the human ileum and circulate in greatly increased concentrations in patients with the watery diarrhoea syndrome. We have infused PHM (23 pmol/kg/min) into 5 patients with ileostomies to determine the effect of PHM on human ileal output. Plasma PHM levels rose from 22 +/- 6 to 6013 +/- 874 pM (mean +/- S.E.M.) during PHM infusions and ileal output rose from 16 +/- 3 to 177 +/- 27 g/30 min (P less than 0.0001). PHM infusions also produced a significant fall in the percentage of solid material and a rise in the concentration of chloride in the ileal effluent. Mean plasma PHM concentrations during PHM infusions were equal to the highest levels seen in patients with the watery diarrhoea syndrome, so PHM may contribute to diarrhoea in this condition. Neuronal PHM may exert physiological control over ileal transport of water and electrolytes.

Survey of distribution of substance P, vasoactive intestinal polypeptide, cholecystokinin, neurotensin, Met-enkephalin, bombesin and PHI in the spinal cord of cat, dog, sloth and monkey

Levels of substance P (sP), peptide-histidine-isoleucine (PHI), vasoactive intestinal polypeptide (VIP), cholecystokinin (CCK), neurotensin (NT), bombesin (BOM) and methionine-enkephalin (Met-Enk) like immunoreactivity were measured in cat, dog, primate and sloth cervical, thoracic, lumbar and sacral dorsal and ventral horns and dorsal root ganglia. The levels of peptides in the cat sacral cord and the principal peaks of immunoreactivity on a 10-60% acetonitrile gradient on a C18 reverse phase high performance liquid chromatography (HPLC) were sP (sP1-11: 369 ng/g), PHI (PHI: 271 ng/g), VIP (VIP1-28: 210 ng/g), Met-Enk (Met1-5 and extended forms: 257 ng/g), BOM (BOM1-10 and GRP1-27: 20 ng/g), CCK (CCK-8: 15 ng/g) and NT (NT1-13: 10 ng/g). Consideration of the rostrocaudal levels revealed an approximately even distribution with the exception of VIP and PHI which showed sacral/cervical ratios of 79 and 63. For sP, Met-Enk and BOM dorsal/ventral ratios were greater than 1 at all spinal levels. For VIP, PHI and CCK these ratios were greater than 1 only in the sacral cord. Dorsal root ganglion (DRG) levels of sP, VIP, PHI were readily measurable in single ganglia and covaried with the respective levels in the dorsal cord. Pooled samples of spinal ganglia and the trigeminal ganglia revealed that the relative levels of peptide immunoreactivity were: sP (25 ng/g); VIP (26 ng/g); PHI (28 ng/g); Met-Enk (6 ng/g); CCK (2 ng/g); NT (1 ng/g); and BOM (1 ng/g).