Stimulating effect of bombesin on the growth of gastrointestinal tract and pancreas in suckling rats

Elevated gastrin-releasing peptide receptor mRNA expression in buccal mucosa: association with head and neck squamous cell carcinoma

BACKGROUND

Expression of gastrin-releasing peptide receptor (GRPR) is elevated in mucosa adjacent to head and neck squamous cell carcinoma (HNSCC) compared with mucosa from cancer-free controls, suggesting elevated GRPR expression may indicate presence of HNSCC.

METHODS

We measured GRPR mRNA levels in histologically normal buccal mucosa from 65 surgical patients with HNSCC and 75 cancer-free control subjects using quantitative polymerase chain reaction (PCR). We tested for association between GRPR expression and HNSCC and evaluated differences in patient progression-free survival (PFS).

RESULTS

Buccal GRPR expression was higher in cases but not controls who were active smokers (p = .04). High GRPR expression was associated with HNSCC (odds ratio [OR] = 3.55; 95% confidence interval [CI] = 1.15-10.93), even after adjustment for age, sex, tobacco use, and sample storage time. PFS did not differ between patients with HNSCC with high versus low GRPR expression (p = .22).

CONCLUSION

Elevated buccal GRPR expression was significantly associated with HNSCC independent of known risk factors but was not an indicator of disease prognosis.

Gastrin-releasing peptide receptor expression in non-cancerous bronchial epithelia is associated with lung cancer: a case-control study

Background

Normal bronchial tissue expression of GRPR, which encodes the gastrin-releasing peptide receptor, has been previously reported by us to be associated with lung cancer risk in 78 subjects, especially in females. We sought to define the contribution of GRPR expression in bronchial epithelia to lung cancer risk in a larger case-control study where adjustments could be made for tobacco exposure and sex.

Methods

We evaluated GRPR mRNA levels in histologically normal bronchial epithelial cells from 224 lung cancer patients and 107 surgical cancer-free controls. Associations with lung cancer were tested using logistic regression models.

Results

Bronchial GRPR expression was significantly associated with lung cancer (OR = 4.76; 95% CI = 2.32-9.77) in a multivariable logistic regression (MLR) model adjusted for age, sex, smoking status and pulmonary function. MLR analysis stratified by smoking status indicated that ORs were higher in never and former smokers (OR = 7.74; 95% CI = 2.96-20.25) compared to active smokers (OR = 1.69; 95% CI = 0.46-6.33). GRPR expression did not differ by subject sex, and lung cancer risk associated with GRPR expression was not modified by sex.

Conclusions

GRPR expression in non-cancerous bronchial epithelium was significantly associated with the presence of lung cancer in never and former smokers. The association in never and former smokers was found in males and females. Association with lung cancer did not differ by sex in any smoking group.

Hormonal control of pancreatic growth during fetal, neonatal and adult life

This review article has for major objective to summarize the old and latest developments on the hormonal controls of pancreatic growth. The article deals with hormonal controls during the fetal, neonatal and adult periods of pancreas development, growth and regeneration. During the fetal period, comparisons were made between studies performed with pancreatic explants and those designed in vivo. After birth, the effects of glucocorticoids, thyroxine, gastrin, bombesin, secretin, cholecystokinin alone or with secretin are reported. In the adults, similar studies were reported on hormones with addition of the effects of neuropeptides, the cell types targeted by hormones and the hormonal control after pancreatectomy and pancreatitis.

Bombesin stimulates enterocyte turnover following massive small bowel resection in a rat

Recent evidence suggests that bombesin (BBS) is involved in modulation of growth and differentiation of normal small intestine. The purpose of the present study was to evaluate the effects of BBS on enterocyte turnover after massive small bowel resection in a rat. Male Sprague-Dawley rats were divided into three experimental groups: Sham rats underwent bowel transection and re-anastomosis, short bowel syndrome (SBS) rats underwent a 75% small bowel resection, and SBS-BBS rats underwent bowel resection and were treated with BBS given subcutaneously at a dose of 20 mug/kg, once daily, from postoperative day 3 through 14. Parameters of intestinal adaptation (bowel and mucosal weights, mucosal DNA and protein, villus height and crypt depth), enterocyte proliferation and enterocyte apoptosis were determined in jejunum and ileum on day 15 following operation. RT-PCR technique was used to determine Bax and Bcl-2 gene expression in ileal mucosa. Statistical analysis was performed using the non-parametric Kruskal-Wallis ANOVA test, with P less than 0.05 considered statistically significant. Treatment with BBS resulted in a significant increase in ileal bowel and mucosal weight, ileal mucosal DNA and protein, jejunal and ileal villus height, jejunal crypt depth, and jejunal and ileal proliferation index compared to SBS-animals. SBS rats showed a significant increase in Bax and Bcl-2 expression in ileum that was accompanied by a significant increase in cell apoptosis compared to sham animals. SBS-BBS rats demonstrated a significant decrease in Bax and Bcl-2 expression in ileum and a decrease in apoptotic index compared to SBS-animals. In conclusion, in a rat model of SBS, BBS enhances enterocyte turnover and stimulates structural intestinal adaptation. Decreased Bax expression may be responsible for the inhibitory effect of BBS on enterocyte apoptosis.

Gastrin-releasing peptide and cancer

Over the past 20 years, abundant evidence has been collected to suggest that gastrin-releasing peptide (GRP) and its receptors play an important role in the development of a variety of cancers. In fact, the detection of GRP and the GRP receptor in small cell lung carcinoma (SCLC), and the demonstration that anti-GRP antibodies inhibited proliferation in SCLC cell lines, established GRP as the prototypical autocrine growth factor. All forms of GRP are generated by processing of a 125-amino acid prohormone; recent studies indicate that C-terminal amidation of GRP18-27 is not essential for bioactivity, and that peptides derived from residues 31 to 125 of the prohormone are present in normal tissue and in tumors. GRP receptors can be divided into four classes, all of which belong to the 7 transmembrane domain family and bind GRP and/or GRP analogues with affinities in the nM range. Over-expression of GRP and its receptors has been demonstrated at both the mRNA and protein level in many types of tumors including lung, prostate, breast, stomach, pancreas and colon. GRP has also been shown to act as a potent mitogen for cancer cells of diverse origin both in vitro and in animal models of carcinogenesis. Other actions of GRP relevant to carcinogenesis include effects on morphogenesis, angiogenesis, cell migration and cell adhesion. Future prospects for the use of radiolabelled and cytotoxic GRP analogues and antagonists for cancer diagnosis and therapy appear promising.

Mitogenic effects of both amidated and glycine-extended gastrin-releasing peptide in defunctioned and azoxymethane-treated rat colon in vivo

Although there is abundant evidence that gastrin-releasing peptide acts as a mitogen in various carcinoma cell lines, the effect of administration of gastrin-releasing peptide on the colorectal mucosa in vivo has not been reported. The aims of this study were to determine whether continuous infusion of gastrin-releasing peptide stimulated proliferation or accelerated carcinogenesis in the rat gastrointestinal tract and other organs. The possible requirement for C-terminal amidation for mitogenic activity in vivo was also investigated. Proliferation was measured in the colon by metaphase index and by immunostaining for the proliferation marker Ki-67, and in other tissues by immunostaining alone. Acceleration of colorectal carcinogenesis was assessed by counting aberrant crypt foci after treatment with the carcinogen azoxymethane. Defunctioning of the rectum reduced both the proliferative index and the crypt height of the rectal mucosa of untreated rats. Treatment with amidated or glycine-extended gastrin-releasing peptide for 4 weeks using implanted mini-osmotic pumps resulted in a two- to three-fold increase in proliferation, and an increase in crypt height, in the defunctioned rectal mucosa (p<0.001), with smaller but significant increases in the caecum and distal colon. No changes in proliferation were detected in lung, pancreas or gastric mucosa. The numbers of aberrant crypt foci in the mid-colon, distal colon and rectum following treatment with azoxymethane were also significantly increased by infusion with amidated or glycine-extended gastrin-releasing peptide. We conclude that administration of gastrin-releasing peptide to mature rats stimulates proliferation and accelerates carcinogenesis in the colorectal mucosa, and that C-terminal amidation is not essential for either effect. Gastrin-releasing peptides could thus potentially act as promoters of colorectal carcinogenesis.

Bombesin in short bowel syndrome

Short bowel syndrome comprises the sequel of nutrient, fluid, and weight loss that occurs subsequent to greatly reduced functional surface area of the small intestine. The aim of this study is to investigate the trophic and functional effects of bombesin on remaining gut in rats with experimentally induced short bowel syndrome. Thirty-two rats were allocated randomly and experimental short bowel syndrome was induced by 80% bowel resection in all rats. A regular enteral diet and isocaloric elemental enteral nutrition for 12 days were given in the control group and the elemental nutrition group, respectively. In the bombesin group 10 microg/kg subcutaneous bombesin (t.i.d.) for 10 days with regular enteral diet for 12 days was given. In the elemental nutrition and bombesin group the diet consisted of 10 microg/kg subcutaneous bombesin (t.i.d.) for 10 days with isocaloric elemental enteral nutrition for 12 days was given. All rats underwent physical, histological, and biochemical evaluation. Reduction in weight loss, bowel diameter, fecal fat content, and glycemia, increase in cellularity, and d-xylose absorption were observed in all treatment groups. These changes were more evident in the bombesin treatment groups. Increases in serum protein and albumin levels were seen with bombesin treatment with or without elemental diet, whereas reductions in villous height and crypt depth were observed only with bombesin treatment without elemental diet. Serum calcium, iron, and vitamin B(12) levels were not affected with any treatment. It is concluded that bombesin may be a useful trophic agent contributing to increased absorptive capacity and improved biochemical values even in the absence of elemental nutrition.

Role of gastrointestinal hormones in the proliferation of normal and neoplastic tissues

Gastrointestinal (GI) hormones are chemical messengers that regulate the physiological functions of the intestine and pancreas, including secretion, motility, absorption, and digestion. In addition to these well-defined physiological effects, GI hormones can stimulate proliferation of the nonneoplastic intestinal mucosa and pancreas. Furthermore, in an analogous fashion to breast and prostate cancer, certain GI cancers possess receptors for GI hormones; growth can be altered by administration of these hormones or by blocking their respective receptors. The GI hormones that affect proliferation, either stimulatory or inhibitory, include gastrin, cholecystokinin, gastrin-releasing peptide, neurotensin, peptide YY, glucagon-like peptide-2, and somatostatin. The effects of these peptides on normal and neoplastic GI tissues will be described. Also, future perspectives and potential therapeutic implications will be discussed.

Growth hormone effects in intestinal adaptation after massive bowel resection in the suckling rat

BACKGROUND

Massive small bowel resection provokes intestinal malabsorption that leads to diminished growth in the suckling rat. Growth hormone is one of the several factors that can enhance the adaptive response of the intestines in the adult rat; however, whether it also enhances postresection intestinal adaptation in the suckling rat, thus reducing the adverse effects of resection on growth, is still unclear.

METHODS

Seventy-four 30-day-old suckling Wistar rats underwent 80% midgut bowel resection, laparotomy (sham operation), or no surgery. They were treated with either growth hormone or saline for 15 days and studied 15 or 45 days after surgery. Body weight was monitored and samples of bone and intestinal mucosa were obtained at the end of the study period for analysis.

RESULTS

Resected rats lost body and bone weight regardless of growth hormone administration. Bowel resection provoked significant increases in the proliferation and size of the intestinal mucosa. Growth hormone significantly, but just barely, increased crypt height and mucosal mass at day 15 after surgery, but not at day 45. Lengthening of the intestines was the main effect of growth hormone.

CONCLUSIONS

The relatively small adaptive response of intestines to growth hormone is insufficient to promote body growth after intestinal resection in the suckling rat. This response is lower than that in older rats and may reflect an age-related differential response to growth hormone.

Activation of MAP kinases in growth responsive pancreatic cancer cells

The implication of MAP kinases in the proliferation control of pancreatic cancer cells is still unknown. This study was undertaken to examine the contribution of the p44/p42 and p38 MAP kinases in the mitogenic response to epidermal growth factor (EGF) and bombesin in human pancreatic cancer cells, MIA PaCa-2 and PANC-1. Data indicate that EGF and bombesin stimulated growth of both cell lines. In MIA PaCa-2 cells, EGF and bombesin stimulated the in gel activation of p38 while p44/p42 kinases exhibited high basal activity and no response to stimuli. Growth and p38 activation were inhibited by genistein, wortmannin, PD98059 and SB203580, specific inhibitors of tyrosine kinase, phosphatidylinositol 3-kinase, MEK-1 and p38 kinases, respectively. In PANC-1 cells, EGF and bombesin stimulated p42 in gel activation; p44 remained highly activated and unresponsive to stimuli and p38 did not respond. Stimulated growth and p42 activation were inhibited by genistein, wortmannin and PD98059. Estimation of MAPK activities with a specific anti-active MAP kinase antibody indicated, however, that EGF increased the intensity of the bands corresponding to p42 and p44 MAP kinases in both cell lines, indicating that the mitogenic factor can regulate MAP kinase activity. Data also pointed out that ATP is sufficient to increase MAP kinase activity within the in gel assay technique and may thus explain the discrepancies existing between the in gel assay data and those obtained with the anti-active MAP kinase antibody.

Bombesin-induced pancreatic regeneration in pigs is mediated by p46Shc/p52Shc and p42/p44 mitogen-activated protein kinase upregulation

BACKGROUND

In several animal species the pancreas has the capacity to partially regenerate in a self regulating process. A complex network of growth factors modulates this process. There is evidence that bombesin stimulates pancreatic regeneration in rodents. Whether bombesin stimulates pancreas regrowth in large mammals is unknown. Shc proteins, the target of tyrosine kinase-coupled receptors, activate p42 and p44 mitogen-activated protein (MAP) kinase and induce the transcriptional upregulation of genes involved in cell proliferation. The aims of our study were to determine whether bombesin stimulates pancreatic growth in large mammals and whether this event requires Shc-MAP kinase pathway upregulation.

METHODS

Three groups of pigs were submitted to sham operation (group 1); to subtotal (70%) distal pancreatectomy (group 2), and to subtotal pancreatectomy followed by bombesin (5 mg three times daily) for 4 weeks (group 3). After a 4-week follow-up a second laparotomy was performed, and the residual pancreas removed. p46Shc, p52Shc and p66Shc, Grb2, and p42/p44 MAP kinase expression and phosphorylation were measured either in freshly isolated pancreatic acinar cells or whole pancreatic extracts.

RESULTS

In vivo bombesin administration resulted in: 1) approximately 100% growth of pancreatic duodenal lobe; 2) rapid recovery from exocrine pancreatic failure; and 3) a threefold increase in the rate of pancreatic acinar cell proliferation. Incubating freshly isolated pancreatic acinar cells with bombesin resulted in time- and concentration-dependent stimulation of p46Shc/p52Shc phosphorylation, Shc-Grb2 complex formation, and p42/p44 MAP kinase activation. In vivo bombesin administration significantly upregulated p46Shc/p52Shc and MAP kinase expression and/or activity in whole pancreatic extracts.

CONCLUSIONS

In vivo chronic bombesin administration stimulates pancreatic regeneration after pancreatectomy in large mammals. Bombesin-stimulated pancreatic growth is associated with upregulation of the Shc-Grb2-SOS-Ras-MAP kinase pathway.

Growth stimulation of normal melanocytes and nevocellular nevus cells by gastrin releasing peptide (GRP)

In order to know the possible effects of gastrin releasing peptide (GRP) on nevus cells and melanocytes, we studied the effect of GRP on the proliferation of cultured human nevus cells and normal melanocytes. MTS assay showed that GRP stimulated the growth of viable melanocytes at 1000 ng/ml. GRP also stimulated the growth of nevus cells in a dose dependent manner and maximum stimulation was obtained at 100 ng/ml of GRP. GRP was less effective for growth stimulation of normal melanocytes than nevus cells. The cytoplasm of nevus cells were positively stained by polyclonal anti-GRP antibody. We also detected the expression of GRP and GRP receptor mRNAs in these cells by RT-PCR. These results suggest that GRP acts as an autocrine growth factor for nevus cells and normal melanocytes.

Effect of the gastrin-releasing peptide antagonist BIM 26226 and lanreotide on an acinar pancreatic carcinoma

The effects of a potent specific gastrin-releasing peptide receptor antagonist, BIM 26226 ([D-F5 Phe6, D-Ala11] bombesin (6-13) OMe), and the long-acting somatostatin analogue, lanreotide (BIM 23014), on the growth of an acinar pancreatic adenocarcinoma growing in the rat or cultured in vitro were investigated. Lewis rats bearing a pancreatic carcinoma transplanted s.c. in the scapular region, were treated with gastrin-releasing peptide (30 microg/kg per day), BIM 26226 (30 and 100 microg/kg per day) and lanreotide (100 microg/kg per day) alone or in combination for 14 successive days. Chronic administration of BIM 26226 and lanreotide significantly inhibited the growth of pancreatic tumours stimulated or not by gastrin-releasing peptide (GRP), as shown by a reduction in tumour volume, protein, ribonucleic acid, amylase and chymotrypsin contents. This effect was more pronounced with 100 microg/kg per day BIM 26226 than with 30 microg/kg per day. However, BIM 26226 and lanreotide, given together, did not exert any additive effect on GRP-treated and -untreated tumours. In cell cultures, both BIM 26226 and lanreotide (10(-6) M) inhibited [3H]thymidine incorporation in tumour cells induced or not by GRP, but no increased effect was observed after combined treatment with both agents. Binding studies showed that BIM 26226 had a high affinity for GRP receptors in tumour cell membranes (IC50 = 6 nM). These results from in vivo and in vitro experiments suggest that BIM 26226 and lanreotide are able to reduce the growth of an experimental acinar pancreatic tumour. Thus, these agents represent interesting steps toward the development of new approaches for treatment of pancreatic carcinomas.

Age-related changes of serum progastrin-releasing peptide levels during childhood

Gastrin-releasing peptide (GRP) has attracted much attention in recent years because it has become recognized as a significant tissue-specific growth factor. To investigate the physiological significance of this peptide in growing children, the time course of serum ProGRP(31-98) level, a precursor hormone of GRP, in children was assessed. A total of 118 serum samples including cord blood was examined with informed consent by using a specific enzyme-linked immunosorbent assay (ELISA) system to measure serum ProGRP(31-98). The serum ProGRP(31-98) level was highest in cord blood and neonatal samples, rapidly declined by 1 year of age and then gradually declined to the adult level by 5 years of age. This time-dependent change of serum ProGRP(31-98) level suggests the importance of GRP as a physiological growth factor in fetal and neonatal tissues.

Effects of exogenous neurotensin on intestinal postresectional growth in the suckling rat

BACKGROUND

In the suckling rat, massive bowel resection provokes intestinal malabsorption that leads to diminished growth. The object of this report was to test whether neurotensin, intestinal trophic peptide, enhances postresection intestinal adaptation, improving absorption and reducing the adverse effects of resection on growth.

METHODS

Fifty-seven 15-day-old suckling. Wistar rats were divided into four groups: 41 rats were subjected to resection of 90% of their small bowel, while the rest (n = 16) underwent laparotomy. Half of the animals, resected and laparotomized, were treated with neurotensin for 30 days. The body weight was monitored, and samples of bone and intestinal mucosa were obtained at the end of the study period for analysis. Blood was tested to determine iron, ferritin, folic acid, and vitamin B12 levels.

RESULTS

The resected animals lost body weight regardless of neurotensin administration. In the resected animals, femur weight increased significantly when they received neurotensin. Bowel resection provokes significant increases in the intestinal mucosa (crypts and villi), but after neurotensin administration, significant increases were detected only in the jejunum of the resected animals but not in the ileum of laparotomized rats. In the resected animals, significant decreases in iron, ferritin, folic acid, and vitamin B12 levels were observed. The postresection administration of neurotensin only produced a significant rise in the ferritin concentration.

CONCLUSIONS

In the suckling rat, neurotensin enhances the intestinal proliferative phenomenon but does not improve the course of medium-term postresection growth.

Regulation of colonic ion transport by GRP. I. GRP stimulates transepithelial K and Na secretion

Regulation of electrolyte transport across porcine distal colon epithelium by gastrin-releasing peptide (GRP) was examined using mucosal sheets mounted in Ussing chambers. Serosal GRP produced a biphasic response consisting of a transient increase in short-circuit current (ISC) followed by a long-lasting decrease. Indomethacin and tetrodotoxin inhibited the ISC increase without affecting the secondary decrease. Addition of GRP to the mucosal solution produced a decrease in ISC similar to that observed with serosal treatment, but no transient increase in ISC was observed. GRP and bombesin (50% effective concentrations of 26 and 30 nM, respectively) were more effective than neuromedin B in decreasing the ISC, and the GRP receptor antagonist [D-Phe(6)]bombesin(6-13)-O-methyl produced a sixfold dextral shift in the GRP concentration-response relationship. The GRP-stimulated decrease was reduced in the absence of Cl and by serosal bumetanide. Flux measurements showed that GRP increased Rb and Na secretion while having no effect on transepithelial Cl transport. Phosphoinositide turnover was increased by GRP, suggesting that the ion transport changes may be mediated by intracellular Ca concentration. The results of this study demonstrate that GRP stimulates K and Na secretion across the porcine distal colon epithelium and that these processes are dependent, in part, on a bumetanide-sensitive transport pathway located in the basolateral membrane.

Growth and propagation of normal rat intestinal epithelial cells

A combination of mild proteolytic digestion and selective growth stimulation has been used to isolate and propagate adult rat intestinal epithelial cells with a finite life span. Growth of these cells on a variety of matrices and on mesenchymal cells has resulted in the expression of brush border enzymes including sucrase-isomaltase, aminopeptidase N, and alkaline phosphatase. Examination of the cells at the electron microscopic level has revealed that although these cells express key brush border enzymes, they do not have a fully formed brush border. These findings suggest that the expression of brush border enzymes and structural proteins represent distinct stages of enterocyte differentiation that are under separate transcriptional and temporal control.

Secretion of gastrin-releasing peptide by retroperitoneal tumors

PURPOSE

Gastrin-releasing peptide (GRP) is a neuropeptide with growth factor activity in vitro for a variety of tumors including neuroblastoma. If GRP is secreted by neuroblastomas, its detection in serum might be an excellent way to both diagnose and monitor this tumor in patients.

METHODS

Small portions of resected tumor specimens were maintained in tissue culture as tumor explants for 24 hours. The tumors included: 3 ganglioneuromas, 1 neuroblastoma, 1 primitive neuroectodermal tumor, 1 Wilms' tumor, 1 rhabdoid tumor, and 1 benign brachial plexus tumor. Control flasks were maintained simultaneously under identical conditions. After 24 hours of incubation, the tumor-conditioned media and the control media were assayed in duplicate for [GRP] using a radioimmunoassay.

RESULTS

All the conditioned media from the benign tumors contained < 25 pg/mL net GRP, whereas all the malignant tumor-conditioned media contained > or = 45 pg/mL (P = 0.003).

CONCLUSIONS

These data suggest that GRP is secreted by pediatric retroperitoneal tumors and that the amount secreted varies directly with the degree of malignancy of the tumor. This study suggests that GRP may be a candidate tumor marker for pediatric retroperitoneal tumors.

Developmental expression of transforming growth factor-alpha and epidermal growth factor receptor proteins in the human pancreas and digestive tract

This study was designed to localize transforming growth factor alpha (TGF-alpha) and epidermal growth factor receptor (EGFR) expression in the developing human gastrointestinal tract and pancreas. Immunohistochemical techniques using specific antibodies against human TGF-alpha and EGFR were performed on digestive tissues of fetuses from 9 to 10 to 24 weeks of gestation, children and adults. In fetuses, TGF-alpha and EGFR proteins were expressed in all epithelial tissues studied with a good correlation and from an age as early as 9 to 10 weeks of gestation, except for TGF-alpha in the esophagus. The strongest TGF-alpha immunostaining was noted in the stomach and the proximal colon. Unexpectedly, immunoreactive gut endocrine cells were observed with the two antibodies used. Relatively numerous in fetuses, they decreased in number with age and were rare in adults particularly along the colon. Enteroglucagonsecreting cells were shown to express TGF-alpha, while some gastrin, somatostatin and pancreatic glucagon cells were immunostained with EGFR antibodies. The presence of TGF-alpha and its receptor in digestive tract epithelium and pancreatic tissues early in fetal life suggests a functional role for TGF-alpha during the developmental process of the digestive system. We demonstrate that TGF-alpha is also produced by endocrine cells and might have an additional mode of action other than paracrine, at least during fetal life.

Bombesin improves survival from methotrexate-induced enterocolitis

OBJECTIVE

The authors determined whether bombesin could improve survival from methotrexate (MTX)-induced enterocolitis.

SUMMARY BACKGROUND DATA

Bombesin prevents gut mucosal atrophy, which is produced by feeding rats an elemental diet. Administration of MTX produces a lethal enterocolitis in rats fed an elemental diet.

METHODS

On treatment day 0, 60 rats were divided randomly into three groups and fed an elemental diet (Vivonex TEN, Sandoz, Minneapolis, MN) as the only source of nutrition. Groups were subdivided further to receive either saline or bombesin (10 micrograms/kg, subcutaneously, three times a day) beginning either on day 0 or day 14. Methotrexate (20 mg/kg, intraperitoneally) was given to all rats 14 days after the start of an elemental diet.

RESULTS

Bombesin prevented the mucosal atrophy in the ileum produced by the elemental diet and significantly decreased mortality in rats given MTX (whether given as a pretreatment or at the time of MTX administration).

CONCLUSION

Bombesin significantly improved survival in a lethal model of MTX-induced enterocolitis, possibly by maintaining gut mucosal structure. Administration of bombesin to patients receiving chemotherapy may be clinically useful in preventing the severe enterocolitis induced by various chemotherapeutic agents.

Gut hormones, growth and malignancy

There is now clear-cut evidence that polypeptide growth factors control the proliferation of the normal gastrointestinal mucosa. Epidermal growth factor (EGF) stimulates normal growth throughout the gastrointestinal tract, and accelerates the healing of ulcerated epithelium. While the effects of gastrin were at first thought to be similarly widespread, the gastrin target now appears to be restricted to the enterochromaffin-like cells in the stomach. Isolated reports suggest that several other hormones, including fibroblast growth factor and the insulin-like growth factors, have similar proliferative effects. In contrast, indirect evidence suggests that somatostatin and transforming growth factor-beta inhibit the growth of the gastrointestinal mucosa. The same growth factors profoundly affect the growth of some gastrointestinal carcinomas. Prolonged hypergastrinaemia increases the risk of development of gastric endocrine tumours, but has no effect on the incidence of gastric adenocarcinoma. Gastrin also stimulates the in vivo growth of 50% of gastric and colorectal carcinoma xenografts, but has no consistent effect on the growth of carcinoma cell lines in vitro. EGF, on the other hand, significantly stimulates proliferation of many gastrointestinal cell lines in culture. Interest has recently focused on autocrine stimulation of gastrointestinal carcinoma growth. Elevated levels of EGF receptor, and of EGF or related mRNAs, have been demonstrated in gastric carcinomas, and the growth of some gastrointestinal cell lines is inhibited by antibodies against EGF, and by antisense oligonucleotides based on EGF mRNA. Similarly gastrin/cholecystokinin antagonists inhibit the growth of several colon carcinoma cell lines, although the spectrum of antagonist potencies suggests that classical gastrin and cholecystokinin receptors are not necessarily involved. Continued research on antagonists may therefore lead to novel therapies for gastrointestinal cancers.

Trophic effects of neurotensin in massive bowel resection in the rat

The trophic effect of the administration of exogenous neurotensin on the intestinal mucosa was studied in rats following an 80% bowel resection. Villus length and mucosal DNA content were assessed in the jejunal and ileal mucosa of the remnant intestine 14 days after resection. The data obtained in an 80% resected control group (80% group) and an experimental group receiving an infusion of neurotensin (300 micrograms/kg/day) for 14 days subcutaneously (80% + NT group) were compared. The results indicate that the administration of exogenous neurotensin (80% + NT) increases villus length (jejunum: 920 +/- 77 vs 861 +/- 25 microns and ileum length: 975 +/- 23 vs 875 +/- 99 microns) to an extent greater than that observed in the 80% resected group not receiving exogenous neurotensin. The levels of mucosal DNA per milligram of protein increased significantly in both groups but was paradoxically less in the 80% + NT group than in the 80% resection group (jejunum: 8.12 +/- 0.56 vs 10.18 +/- 0.80; ileum: 8.63 +/- 0.43 vs 10.05 +/- 0.46). These data suggest that the administration of exogenous neurotensin to the rat potentiates the growth of intestinal villi and accelerates the intestinal trophic response seen following massive bowel resection. The increase in circulating enteroglucagon levels noted after neurotensin administration (80% + NT: 547 +/- 48 pg/ml vs 80%: 341 +/- 41 pg/ml) suggests that some of the trophic effects of neurotensin may be mediated, at least in part, by enteroglucagon. These data also suggest a potential role for the use of neurotensin in the initial treatment of individuals with short bowel syndrome.

Humoral regulation of intestinal adaptation

After the loss of small bowel through disease or surgery the residual bowel adapts by increasing its functional capacity. This process of adaptation involves dilatation, hypertrophy and mucosal hyperplasia, particularly distal to the area of bowel loss or disease. The response of the residual bowel is mediated by a complex interplay of factors including luminal nutrition, pancreaticobiliary secretions, luminal or local growth factors and also humoral or endocrine factors. The experimental model commonly used to characterize the adaptive response, massive small bowel resection (MSBR), involves 80% resection of the small bowel in the rat. Of the various putative humoral factors, most work has focused on the products of the ileal L cells: enteroglucagon and peptide YY. Plasma levels of both hormones are increased after MSBR and indeed their mRNA levels are also increased as a result of an increase in the amount of message per L cell. Whilst PYY probably serves as an 'ileal brake' to slow the movement of the luminal contents and hence increase their mucosal contact time, the role of the enteroglucagon is unresolved. The molecular cloning of the proglucagon gene has revealed, firstly, that there are a number of biologically active peptides which derive from the propeptide and, secondly, that tissue-specific differential processing occurs. Most studies do not clearly define which of these products of proglucagon is being measured and is termed as glucagon-like or enteroglucagon immunoreactivity. The insulin-like growth factors (IGF) have a potent mitogenic action on the bowel. Their role after MSBR is likely to be largely paracrine. Though IGF-I mRNA levels do not increase after MSBR, the precipitous and early fall in ileal IGF-binding protein-3 (IGFBP-3) mRNA levels suggests a fall in IGFBP-3 levels may increase local IGF-I bioactivity. Polyamine synthesis is a critical component of the adaptive response, although the stimulus to their dramatic increase in synthesis after MSBR remains to be elucidated. Other humoral factors such as cholecystokinin, neurotensin and bombesin probably have minor indirect roles in the adaptive response. Components of the epidermal growth factor/transforming growth factor alpha response pathway family of growth factors may be involved as paracrine regulators. There is thus strong evidence that humoral factors play an important role in intestinal adaptation; characterization of the nature of the humoral factors and their relationship with other influences such as luminal nutrition and pancreatic biliary secretions may facilitate the development of new therapeutic strategies for the short bowel syndromes.

The effect of prolactin and bombesin on the growth of meningioma-derived cells in monolayer culture

Meningioma growth is thought to be stimulated by the sex hormones progesterone and possibly estrogen. We report here stimulation of growth of meningioma-derived cells in culture by prolactin. Fourteen human tumors taken from surgery were initially grown in Ham's medium F10 with 15% fetal calf serum. The tumors were then trypsinized and resuspended in medium in a multi-well plate with either prolactin or bombesin; the cells were incubated for 1 week, washed, and resuspended for cell counting. The growth-stimulating effect of prolactin at 10 and 200 micrograms/ml was compared with bombesin at 5 mM/ml or 15 mM/ml. A growth index compared cell count in the experimental well to the control well; growth at the rate of the control well was given an index of 1.0. The tumors included 7 meningiomas and 7 other neoplasms (3 astrocytomas, an ependymoma, a pineoblastoma, a hemangiopericytoma, and a metastatic adenocarcinoma). For meningiomas incubated in 10 micrograms/ml prolactin, the growth index was 3.08; for those incubated in 200 micrograms/ml prolactin, it was 2.28. Bombesin indices were 1.7 and 1.2 at 5 mM/ml and 15 mM/ml, respectively. By 2-tailed t-testing both prolactin concentrations stimulated the growth of meningiomas significantly (P < or = 0.02), while bombesin did not. Neither peptide enhanced the growth of the other tumors tested.

Somatostatin inhibition of phosphoinositides turnover in isolated rat acinar pancreatic cells: interaction with bombesin

The effects of somatostatin-14 and bombesin on [3H]inositol phosphate accumulation were studied in 24 h myo-[3H]inositol-prelabeled cultured rat acinar cells. Bombesin, 10 nM, stimulated basal formation of phosphatidyl monophosphate (InsP1), phosphatidyl 4,5-biphosphate (InsP2) and inositol 1,4,5-triphosphate (InsP3) by 128 +/- 5.2%, 147 +/- 10% and 155 +/- 5%, respectively. At 5 s, the ED50 value for InsP3 stimulation was 0.70 +/- 0.2 nM. This stimulation was partly blocked (64 +/- 0.04% inhibition) by 10 ng/ml Bordetella pertussis toxin. In contrast to bombesin, somatostatin, 10 nM, inhibited basal InsP1, InsP2 and InsP3 formation. At 5 s, the inhibition degree for InsP3 was 18 +/- 2.5% and the IC50s values 1 +/- 0.09 nM, 1 +/- 0.12 nM and 0.07 +/- 0.005 nM for InsP1, InsP2 and InsP3, respectively. Bombesin-stimulated InsP3 formation was also inhibited by somatostatin. At 5 s, the inhibition degree was 85 +/- 3.5% at 10 nM and the IC50 value, 0.10 +/- 0.05 nM. Furthermore, somatostatin inhibition of bombesin stimulation was partly blocked (66 +/- 4% inhibition) by Bordetella pertussis toxin. These data therefore suggest that the acinar pancreatic cells contain a somatostatin receptor exerting a negative control on basal and bombesin receptor-stimulated phosphatidyl inositol turnover.

Direct effect of bombesin on pancreatic and gastric growth in suckling rats

Bombesin stimulates growth of the stomach and pancreas in adult rats. Part of this effect is thought to be through the release of CCK following bombesin treatment. We studied the effect of long term administration of bombesin on the pancreas and stomach in suckling rats and examined the action of bombesin using specific CCK antagonist (CR-1409) and bombesin antagonists (GRP19-26, D-Phe19, Leu26CH2NHCOCH3 = cpd 17; L-686,095-001C002 = cpd 23). Rat pups (7-days-old) were given bombesin (20 micrograms/kg body wt. twice a day) or vehicle (1% gelatin) for 9 days. Bombesin stimulated pancreatic and gastric growth (tissue weight, total protein and DNA content all increased). Pancreatic trypsinogen concentration and content showed a 2-3-fold increase. CR-1409 at 6 mg/kg body wt., a dose that blocked the trophic action of CCK-33 when given to pups at similar ages, did not affect the bombesin-stimulated growth of the pancreas or the increase in trypsinogen level. At 2.4 mg/kg body wt., cpd 17 partially blocked and cpd 23 completely blocked the trophic effect of bombesin on the pancreas and stomach and the increase in trypsinogen level in the pancreas. RU-486, a type II glucocorticoid receptor antagonist, given at a dose sufficient to block the physiological action of glucocorticoid, had no effect on bombesin-stimulated growth of the pancreas. Thus, in vivo, bombesin acts directly on the neonatal pancreas and stomach.

Multiple organ failure. Pathophysiology and potential future therapy

Multiple organ failure (MOF) has reached epidemic proportions in most intensive care units and is fast becoming the most common cause of death in the surgical intensive care unit. Furthermore, in spite of the development of successive generations of new and more powerful antibiotics and increasing sophisticated techniques of organ support, our ability to salvage patients once MOF has become established has not appreciably improved over the last two decades. Clearly, new therapeutic strategies aimed at preventing or limiting the development of the physiologic abnormalities that induce organ failure are needed to improve survival in these critically ill patients. Based on our rapidly increasing knowledge of the mechanisms of MOF and the fruits of molecular biology, a number of new therapeutic approaches are in various stages of development. To effectively use these new therapeutic options as they become available, it is necessary to have a clear understanding of the pathophysiology of MOF. Thus, the goals of this review are to integrate the vast amount of new information on the basic biology of MOF and to focus special attention on the potential therapeutic consequences of these recent advances in our understanding of this complex and perplexing syndrome.

Pre- and post-natal ontogeny of neutral endopeptidase 24-11 ('enkephalinase') studied by in vitro autoradiography in the rat

Neutral endopeptidase (NEP, enkephalinase, CALLA) which is present in various neural and non-neural tissues, is able to cleave a variety of regulatory peptides. The distribution of NEP has been studied during rat pre- and post-natal development by autoradiography after in vitro binding of the tritiated inhibitor [3H]HACBO-Gly to whole-body and organ sections. In the central nervous system (CNS), where the presence of NEP has been related to the termination of the action of enkephalins, the external layer of the olfactory bulbs is the only structure prominently labeled before birth. Other CNS structures rich in NEP in the adult, such as the nigrostriatal tract, are progressively labeled after birth. Outside the CNS, the progressive appearance of NEP in the kidney, the lungs and the salivary glands suggests its concomitant involvement in adult physiological functions, including fluid balance control, possibly by cleaving the atrial natriuretic peptide (ANP) and other peptides. On the other hand, transient or enhanced expression of NEP is observed during the development of several organs such as the sensory organs, the heart and the major blood vessels, the intestine, the bones and the genital tubercle. In addition to the still incompletely known physiological functions of the enzyme, the developmental pattern of its expression in several tissues strongly suggests a modulatory role for NEP in the ontogeny of a large number of organs.

Hyperplasia of bombesin-immunoreactive pulmonary neuroendocrine cells and neuroepithelial bodies in sudden infant death syndrome

The distribution and frequency of bombesin immunoreactive neuroendocrine (NE) cells including neuroepithelial bodies (NEB) was analyzed morphometrically in lung sections from 25 infants who died of sudden infant death syndrome (SIDS) and 25 control infants. The control group included infants age-matched to those with SIDS, as well as subjects ranging in age from early to late infancy, to define the postnatal development of pulmonary NE-cell system. Quantitative analysis was performed on lung sections immunostained with monoclonal antibody against bombesin and the contents of bombesin-like peptide in lung extracts were measured by a specific radioimmunoassay (RIA). In control infants, the frequency of NE cells was high at birth but decreased dramatically during the first year of life. In SIDS infants, the frequency of NE cells, the size of NEB, and the mean concentration of bombesin-like peptide detected by RIA were significantly increased compared to those values for age-matched controls. These findings suggest hyperplasia of bombesin-immunoreactive NE-cell system in the lungs of SIDS infants. Since NEB are thought to function as hypoxia-sensitive airway chemoreceptors and since these cells are prominent in the neonates but decline postnatally, we speculate that chronic hypoxia and/or developmental delay may be responsible for this alteration in the lungs of SIDS victims. Potential dysfunction of pulmonary NE-cell system, compounded by other abnormalities in the autonomic regulation of respiration may be of importance in the pathogenesis of SIDS.

Isolation of a gastrin releasing peptide receptor from normal rat pancreas

The presence of a putative GRP receptor on rat pancreatic particulate membranes was demonstrated by covalent cross-linking to 125I-gastrin releasing peptide (GRP), which revealed a radioactive band with Mr = 80-90 kDa on reduced SDS-PAGE. Fresh rat pancreatic membranes contained a GRP receptor which was solubilized with Triton X-100 as assessed by its failure to sediment at 100,000 x g for one hour and its ability to pass through a 0.22 mu filter. When 125I-GRP binding was studied using Sephadex G50 gel filtration chromatography to separate bound from unbound ligand, substantial amounts of 125I-GRP binding were observed in rat crude solubilized pancreatic membranes, but essentially no specific binding was observed until the crude solubilized membranes were fractionated by ammonium sulfate precipitation. Specific 125I-GRP binding was 500, 700 and 1400 fmol/mg protein, respectively, in the 0-25%, 25-50% and 50-80% saturated ammonium sulfate fractions (125I-GRP concentration = 1 nM). Specific binding was temperature dependent, saturable and of high affinity, (KD = 2.3 nM). A unique 70 kDa band was visualized by silver staining of the SDS-PAGE of eluates of GRP(14-27) affinity gel compared with eluates of control affinity gels incubated with the 25-50% (NH4)2SO4 fraction. The lower Mr than that observed with covalent cross-linking may represent the binding subunit of a larger receptor protein. This ligand-affinity isolated protein is thus a good candidate for the GRP receptor, or the binding subunit of it, from normal rat pancreas.

Effect of secretin on growth of stomach, small intestine, and pancreas of developing rats

Secretin is present in the intestine of a number of developing species, and plasma secretin levels are elevated in newborn pigs and humans. Secretin stimulates the growth and affects the enzymatic composition of the stomach, small intestine, and pancreas in adult rats. This suggests a possible role for secretin in the rapid postnatal growth of these organs. We investigated this hypothesis by injecting rats subcutaneously with secretin (100 micrograms/kg) every 12 hr for seven days beginning on postnatal day 3, 6, 13, or 24. Growth parameters (weight, content of protein, DNA) as well as the composition of organ-specific enzymes of the stomach, small intestine, and pancreas were measured. Secretin increased growth parameters of the stomach and small intestine in a similar pattern, and in a quantitatively different fashion from that observed in the pancreas. Secretin's effects were also dependent on postnatal age for all organs studied. These data demonstrate that secretin can influence organ growth and enzyme composition of the stomach, small intestine, and pancreas of developing rats and may be one factor regulating growth and development of these organs.

Promoting effect of bombesin on the cell proliferation in the rat endocrine pancreas during the early postnatal period

The present work investigated whether orally administered bombesin influences cell proliferation in the endocrine pancreatic islets of rats during the suckling period and after weaning. Four series of pups were given bombesin diluted in milk (20 micrograms/kg, 3 times daily) or milk alone for 5 days during either the first, second, third or fourth postnatal week of life. Oral administration was used because bombesin-like peptides have been identified in the breast milk of mammals. 45 min before death, animals were given a single [3H]thymidine pulse injection. Tissue sections were processed for radioautography; DNA labeling and mitotic indices were estimated after counting at least 1000 endocrine cells per rat pancreas. In control rats, the labeling and mitotic indices in pancreatic islets dropped regularly from the first week to the fourth week of life (3.6% +/- 0.2% versus 1.9% +/- 0.1% and 0.46% +/- 0.09% versus 0.08% +/- 0.02%, respectively). Orogastric bombesin administration significantly increased the DNA labeling and mitotic indices at the end of the first week (+20% and +62%, respectively) and second week of life (+37.5% and +49%, respectively) (P less than 0.05 to P less than 0.005), but did not modify these parameters for the third and subsequent weeks of life. Therefore, this study provides evidence that bombesin stimulates DNA synthesis and cell division in pancreatic endocrine cells during the developmental period.

Pulmonary neuroendocrine cells. Their secretory products and their potential roles in health and chronic lung disease in infancy

Pulmonary neuroendocrine cells (PNEC) are granulated epithelial cells distributed throughout conducting airways. Among the bioactive products identified within the secretory granules of these cells are potent mitogens and bronchoactive and vasoactive agents. The secretory status of these cells, which are in greatest number in the fetus and newborn, is modulated by neural reflexes and by changes in airway gas composition. The aggregate data suggest roles for PNEC in airway "chemoception" and/or regulation of airway epithelial differentiation. Marked increases in PNEC are observed in bronchopulmonary dysplasia, where airway and alveolar fibrosis, epithelial metaplasia, and airway and vascular smooth muscle hypertrophy contribute to marked pathophysiologic changes in lung function. Considering the biologic effects of PNEC secretory products, particularly gastrin-releasing peptide on airway epithelial cell and fibroblast proliferation, we propose that an increase in PNEC secretory products in the regenerating airway epithelium may contribute to the development of the pathologic alterations in lung structure seen in bronchopulmonary dysplasia. In this proposed scheme, secretion of abnormally large amounts of bronchoactive and vasoactive agents from PNEC (e.g., serotonin, gastrin-releasing peptide) in response to airway hypoxia and hypercapnia may be partially responsible in the genesis of reactive airway disease and pulmonary hypertension seen in this disease.

Bombesin: an activator of specific Aeromonas antibody secretion in rat intestine

The effect of bombesin (BBS) in modulating the secretion of specific Aeromonas antibodies in rat intestine was determined. Rats were immunized with the culture supernatant of Aeromonas hydrophila, isolate SSU. This culture supernatant contained a number of toxins that may be considered virulence factors. After 24 days of immunization, rats were anesthetized and a 10-cm intestinal segment was perfused with phosphate-buffered saline. The effluents were collected for measurement of IgA and IgG by the enzyme-linked immunosorbent assay. When compared with the effect of intravenous administration of normal saline in the control group, intravenous injection of BBS (20 micrograms/kg) in the experimental group caused a significant increase in rat intestinal IgA and IgG in perfusates. The stimulatory effects of BBS on the presence of IgA and IgG were depressed partially by proglumide, a receptor antagonist of cholecystokinin (CCK) and gastrin. Treatment with pentagastrin (250 micrograms/kg) accelerated intestinal secretion of IgA, but failed to stimulate intestinal IgG secretion. In addition, intravenous injection of CCK-8 (120 ng/kg) evoked the intestinal secretion of either IgA or IgG. These findings demonstrated that BBS, gastrin, and CCK can stimulate antibody secretion in rat intestine and the stimulatory effect of BBS may be mediated partially via release of CCK and gastrin. These results suggest that neuropeptides such as BBS and gastrointestinal hormones, eg, CCK and gastrin, may participate in the regulation of intestinal secretion of IgA and IgG antibodies, respectively, in rats.

Enzyme immunoassay of gastrin releasing peptide (GRP)-like immunoreactivity in milk

A sensitive and specific enzyme immunoassay (EIA) for gastrin releasing peptide (GRP)-like immunoreactivity was developed using enzyme-labeled antigen. The synthetic carboxy-terminal fragment of human GRP(12-27) was conjugated with beta-D-galactosidase for EIA. The minimum amount of GRP-like immunoreactivity detectable by this method was 0.24 femtomol/well (6 picomol/liter). The level of GRP-like immunoreactive substance in bovine foremilk was about 150 nanomol/liter, the level of which was more than hundredfold higher than that in normal milk or calf serum.

Cholecystokinin receptor antagonism by peptidergic and non-peptidergic agents in rat pancreas

1. Graded doses of bombesin infused I.V. into conscious rats with chronic pancreatic fistulae induced a dose-dependent stimulation of protein secretion, similar to that obtained with caerulein. This stimulation does not appear to be mediated by cholecystokinin (CCK) receptors because peptidergic (CR-1409) and non-peptidergic (L-364718) CCK antagonists failed to affect protein secretion at a dose range which caused almost complete suppression of caerulein-induced pancreatic secretion. 2. Studies in vitro on isolated rat pancreatic acini revealed that caerulein, pentagastrin and bombesin all showed the same efficacy in their ability to stimulate amylase release. In contrast, CCK antagonists competitively inhibited amylase release induced by caerulein and pentagastrin but not by bombesin or urecholine, indicating that the latter two agents act directly on acinar cells via receptors which are separate from those involved in stimulation induced by caerulein and pentagastrin. 3. DNA synthesis, measured by the incorporation of [3H]thymidine into DNA, was significantly stimulated by caerulein, soybean trypsin inhibitor (FOY 305), pentagastrin and by bombesin in a dose-dependent manner. CCK receptor antagonists prevented stimulation of DNA synthesis induced by caerulein, FOY 305 and pentagastrin but not by bombesin. 4. This study indicates that bombesin strongly stimulates pancreatic enzyme secretion, with an efficacy similar to that of caerulein, and also exerts a potent growth-promoting action on the pancreas, both effects appearing to be mediated by mechanisms independent of the CCK receptors.

Study into the role of cholecystokinin in bombesin-stimulated pancreatic growth in rats and hamsters

The effects of cholecystokinin and bombesin on growth of the exocrine pancreas have been studied extensively in rats but not in hamsters. Since hamsters are frequently used for studying pancreatic carcinogenesis it seems highly relevant to determine the effects of these peptides on growth of the hamster pancreas as well. In order to determine whether or not bombesin stimulates pancreatic growth in hamsters and to investigate the role of cholecystokinin in mediating this effect, we conducted a 2-week experiment in which cholecystokinin and bombesin were administered to both rats and hamsters, either with or without lorglumide (CR-1409; a specific cholecystokinin receptor antagonist). Rats were included in the study for comparison. Cholecystokinin and bombesin were found to stimulate pancreatic growth and DNA synthesis in both species. Lorglumide did not significantly influence the effect of bombesin on pancreatic weight but did significantly inhibit DNA synthesis in both species. The effect of cholecystokinin on pancreatic weight was greater in hamsters than in rats. This effect was significantly inhibited by lorglumide in hamsters but not in rats, whereas a significant decrease in DNA content was attained in both species. Thus, this study shows marked differences between rats and hamsters in the pancreatic growth response to cholecystokinin and bombesin.

Influence of cholecystokinin antagonist on the effects of cholecystokinin and bombesin on azaserine-induced lesions in rat pancreas

Both cholecystokinin and bombesin have been shown to promote pancreatic carcinogenesis in the azaserine-rat model. The present study was undertaken to discriminate between the effects of cholecystokinin and bombesin and to establish the modulating properties of the specific cholecystokinin receptor antagonist CR-1409 on pancreatic carcinogenesis. After initiation with 30 mg/kg of azaserine, six groups of 15 Wistar rats were treated for 16 wk with cholecystokinin, bombesin, or gelatin (control), some in combination with CR-1409. Doses of cholecystokinin (2.5 micrograms/kg) and bombesin (10 micrograms/kg) were chosen that rendered approximately equal plasma cholecystokinin levels. Both cholecystokinin and bombesin were found to stimulate pancreatic growth, whereas CR-1409 only inhibited the growth-promoting effect of cholecystokinin significantly. Furthermore, both peptides stimulated the development of putative preneoplastic lesions, whereas CR-1409 only inhibited the effect of cholecystokinin significantly. It is concluded that (a) CR-1409 inhibits the promoting effect of cholecystokinin on pancreatic growth and azaserine-induced early pancreatic lesions and (b) the effects of bombesin cannot be fully ascribed to stimulation of the secretion of endogenous cholecystokinin.

Influence of bombesin on gastrointestinal and pancreatic cell growth in adult and suckling animals

Chronic administration of bombesin in the adult rat affects cell growth and enzyme activities in the pancreas. It also induces hyperplasia of the fundic mucosa, increases antral gastrin content, and stimulates gastrin cell proliferation in the antral mucosa. These effects could be explained by the release of hormones such as gastrin and CCK, whose trophic roles on the digestive tract are well proven. Some arguments raise the possibility that bombesin may also act directly on these organs (i.e., the presence of specific receptors for bombesin, pancreatic changes induced by bombesin and not blocked by a potent, specific CCK receptor antagonist). It may well be that both mechanisms exist simultaneously. In addition, bombesin has a growth-promoting effect on the gastric mucosa and pancreas of suckling rats when administered either subcutaneously or orogastrically. Keeping in mind that the maternal milk contains a bombesin-like immunoreactant peptide, we consider that the latter finding raises questions about the possible physiological role of such a peptide in the regulation of the postnatal development of the gastrointestinal tract.

Oral administration of epidermal growth factor in suckling rats stimulates cell DNA synthesis in fundic and antral gastric mucosae as well as in intestinal mucosa and pancreas

The effect of orogastrically given epidermal growth factor (EGF) on the on the development of the digestive system was examined in suckling rats. In particular, DNA synthesis in progenitor cells of the fundic, antral and ileal mucosae and of the exocrine pancreas was analyzed through tritiated thymidine injection and histoautoradiographic study. EGF (10 or 100 micrograms/kg, 3 times daily) was instilled in pups between the 11th and the 13th day of life. Controls received distilled water in a similar manner. All rats were killed 14th after the last orogastric instillation and 45 min after one pulse injection of tritiated thymidine. The highest dose of EGF increased the antral mucosal height (P less than 0.005), the mean number of epithelial cells per crypt column in ileal mucosa, as well as the cell labeling indices of fundic, antral, ileal mucosae and of pancreatic acinar tissue (P less than 0.001) as compared with controls. The lowest dose of EGF increased the cell labeling indices of antral and ileal mucosae and of the exocrine pancreas (P less than 0.001) but did not modify that of fundic mucosa as compared with controls. It is concluded that (a) orally given EGF stimulates cell proliferation in the digestive system of suckling rats, (b) antral mucosa is more sensitive to EGF than fundic mucosa, (c) it is likely that EGF is absorbed and acts systemically on the pancreas. It remains to be determined whether EGF acts systemically or by activation of luminal receptors, on fundic, antral and ileal mucosae.

Transient elevation of messenger RNA encoding gastrin-releasing peptide, a putative pulmonary growth factor in human fetal lung

Gastrin-releasing peptide (GRP), the mammalian homologue of the amphibian peptide bombesin, is present in pulmonary neuroendocrine cells and appears to be a growth factor for both normal and neoplastic pulmonary cells. Previously we have reported the cloning of the messenger RNAs (mRNAs) and gene that encode human GRP. We now report that GRP mRNAs are markedly elevated in human fetal lung during the canalicular phase of pulmonary development (from approximately 16 to 30 wk gestation). By RNA blot and in situ hybridization analyses, GRP mRNAs were first detectable in fetal lung at 9-10 wk, plateaued at levels 25-fold higher than in adult lungs from 16 to approximately 30 wk and then declined to near adult levels by 34 wk gestation. By contrast, GRP peptide levels remain elevated until several months after birth. Consistent with this, in situ hybridization and immunohistochemical studies showed that GRP mRNA and peptide consistently colocalized in early gestation lung but that in neonatal lung, many cells that contained GRP peptide no longer contained GRP mRNA. The transient expression of high levels of GRP mRNAs during an approximately 12-wk phase of fetal lung development suggests that the secretion of GRP or its COOH-terminal peptides from pulmonary neuroendocrine cells may play a role in normal lung development.