Optimisation of isolation of richly pure and homogeneous primary human colonic smooth muscle cells

BACKGROUND

Inherent properties of gastrointestinal smooth muscle can be assessed using isolated cell suspensions. Currently available isolation techniques, based on short 2-h enzymatic digestion, however, present the disadvantage of low cellular yield with brief viability. These features are an important limiting factor especially in studies in humans in which tissue may not be available daily and mixing of samples is not recommended.

AIMS

To optimise the isolation procedure of cells from human colon to obtain a richly pure primary smooth muscle cell preparation.

METHODS

Slices of circular muscle layer, obtained from surgical specimens of human colon, were incubated overnight in Dulbecco's modified eagle's medium supplemented with antibiotics, foetal bovine serum, an ATP-regenerating system and collagenase. On the following day, digested muscle strips were suspended in HEPES buffer, and spontaneously dissociated smooth muscle cells were harvested and used either immediately or maintained in suspension for up to 72 h. Cell yield, purity, viability, contractile responses, associated intracellular calcium signals and RNA and protein extraction were evaluated and compared to cell suspensions obtained with the current short digestion protocol.

RESULTS AND CONCLUSION

The overnight isolation protocol offers the advantage of obtaining a pure, homogeneous, long-life viable cell suspension that maintains a fully differentiated smooth muscle phenotype unchanged for at least 72 h and that allows multiple functional/biochemical studies and efficient RNA extraction from a single human specimen.

Utility of combined use of plasma levels of chromogranin A and pancreatic polypeptide in the diagnosis of gastrointestinal and pancreatic endocrine tumors

BACKGROUND

Chromogranin A (CgA) is considered the most accurate marker in the diagnosis of gastro-entero-pancreatic (GEP) endocrine tumors. Pancreatic polypeptide (PP) has also been proposed to play this role, but then not used due to its low sensitivity. The aim of the present study was to determine whether the assessment of PP would improve the diagnostic reliability of CgA in patients with GEP tumors.

PATIENTS AND METHODS

Both markers were assessed in 68 patients [28 functioning (F), 40 non functioning (NF)]. Twenty-seven patients disease-free (DF) after surgery, and 24 with non-endocrine tumors (non-ETs) were used as control groups.

RESULTS

CgA sensitivity was: 96% in F, 75% in NF, 74% in pancreatic, and 91% in gastrointestinal (GI) tumors. Specificity was 89% vs DF, and 63% vs non-ETs. PP sensitivity was: 54% in F, 57% in NF, 63% in pancreatic, and 53% in GI tumors. Specificity was 81% vs DF, and 67% vs non-ETs. By combining the two markers a significant gain in sensitivity vs CgA alone was obtained: overall in GEP tumors (96% vs 84%, p = 0.04), in NF (95% vs 75%, p = 0.02), and in pancreatic (94% vs 74%, p = 0.04). More specifically, a 25% gain of sensitivity was obtained in the subgroup of NF pancreatic tumors (93% vs 68%, p = 0.04).

CONCLUSION

The combined assessment of PP and CgA leads to a significant increase in sensitivity in the diagnosis of GEP tumors, particularly in pancreatic NF.

Contribution of NK3 tachykinin receptors to propulsion in the rabbit isolated distal colon

The role of NK3 receptors in rabbit colonic propulsion has been investigated in vitro with the selective agonist, senktide, and two selective antagonists, SR142801 and SB222200. Peristalsis was elicited by distending a rubber balloon with 0.3 and 1.0 mL of water leading to a velocity of 2.2 and 2.8 mm s-1, respectively. At concentrations of 1 nM, senktide inhibited propulsion evoked by both distensions (range 25-40%), whereas at 6 and 60 nmol L-1 facilitated 'submaximal' propulsion by 30%. In the presence of Nomega-nitro-L-arginine (L-NNA, 200 micromol L-1), which per se caused a slight prokinetic effect, 1 nmol L-1 senktide markedly accelerated propulsion (range 35-50%). Hexamethonium (200 micromol L-1) had minor effects on propulsion. In its presence, 60 nmol L-1 senktide significantly inhibited propulsion induced by both stimuli (range 20-50%). SR142801 (0.3, 3 nmol L-1) and SB222200 (30, 300 nmol L-1) facilitated 'submaximal' propulsion (range 20-40%). Conversely, higher antagonist concentrations (SR142801: 30, 300 nM; SB222200: 1, 10 micromol L-1) inhibited propulsion to both distensions by 20%. A combination of SR142801 (300 nmol L-1) plus hexamethonium (200 micromol L-1) induced an approximately four-fold greater inhibition of propulsion than that induced by SR142801 alone. In conclusion, in the rabbit-isolated distal colon, a subset of NK3 receptors located on descending pathways mediates an inhibitory effect on propulsion by activating a NO-dependent mechanism. Another subset of NK3 receptors, located on ascending pathways mediates a facilitative effect involving a synergistic interaction with cholinergic nicotinic receptors.

Efficacy of gluten-free diet alone on recovery from iron deficiency anemia in adult celiac patients

OBJECTIVE

Iron deficiency anemia has been reported as the most frequent extraintestinal symptom in adult celiac disease. Prospective studies on the effect of gluten-free diet on recovery from iron deficiency anemia are lacking. The aim of this study was to verify in adult patients with celiac disease the efficacy of and the time course of recovery from iron deficiency anemia by a gluten-free diet alone.

METHODS

We studied 190 consecutive adult patients with iron deficiency anemia, screened for celiac disease by duodenal biopsies. New diagnosed celiac patients were invited to follow a gluten-free diet alone without iron supplementation. After 6 months of diet, duodenal biopsies were performed and hematological tests were repeated at 6, 12, and 24 months.

RESULTS

Celiac disease was diagnosed in 26 (24 women, 2 men; 13.7%) adult patients. After 6 months of gluten-free diet 14 of 18 (77.8%) female patients recovered from anemia, but only 5 of 18 (27.8%) reversed from iron deficiency. At 12-month control all but one patient (94.4%) recovered from anemia and 9 patients (50%) from iron deficiency. After 24 months of diet, only the patient who did not recover from anemia at 12-month control was still anemic, whereas 10 patients (55.5%) reversed from iron deficiency. A significant inverse correlation (r = -0.7141, p = 0.0003) between increase of Hb concentrations and decrease of individual histological scores of duodenitis was observed.

CONCLUSIONS

A screening for celiac disease should be carried out in adult patients with iron deficiency anemia. Recovery from anemia occurs between 6 and 12 months on a gluten-free diet alone as a consequence of normalization of histological alterations of the intestinal mucosa.

Regional differences in signalling transduction pathways among smooth muscle cells from rabbit colon

Smooth muscle cells (SMC) from the circular muscle layer of rabbit colon, taken from the proximal and distal regions that are known to have different physiological and motor activities, were used to highlight distinct regional intrinsic myogenic properties and to investigate the correlations between receptor and signalling transduction pathways. Contractile agonists were shown to be more potent on proximal than on distal SMC in inducing contraction and intracellular Ca(2+) increase. Concentration-response curves of agonists-induced Ca(2+) increase were constantly shifted to the right, though remaining parallel, with respect to contraction curves, independently of the region analysed. Using agents activating different steps of cAMP-or cGMP-mediated intracellular cascades, main regional differences were revealed as far as relaxation was concerned. Relaxation of proximal SMC was found to be essentially cGMP mediated, while that of distal SMC was cAMP mediated. In conclusion, the motor patterns of the two regions appear to be influenced by distinct regional biochemical characteristics that are intrinsic to colonic SMC.

Progression from homologous to heterologous desensitization of contraction in gastric smooth muscle cells

Acute desensitization of contraction and its relative mechanisms have been studied in smooth muscle cells isolated from guinea pig stomach. Desensitization was induced by pre-exposure of the cells to one of the excitatory neuropeptides linked to the phospholipase C intracellular cascade, i.e., cholecystokinin (CCK), gastrin-releasing peptide, and Substance P. Desensitization was homologous after a 30-s pre-exposure and heterologous if pre-exposure lasted for 5 min or longer. Homologous desensitization was studied in a more detailed way after pre-exposure to CCK. Preincubation with increasing concentrations of CCK (10 pM-1 microM) induced a progressive rightward shift of the dose-response curves associated with both a decrease in potency (ED50 4.5 pM-2.2 nM) and a maximum response that were not related to a modification of response kinetics. After brief pre-exposure to 1 nM CCK (Dmax), an inhibition of contraction was observed in response to an identical dose of CCK (45.1 +/- 8.6%), the decreased response being associated with an inhibition of inositol phosphates and [Ca++]i mobilization. Both inositol trisphosphate (InsP3)-induced contraction and [Ca++]i mobilization were inhibited to a lesser extent than CCK-induced responses. Any longer pre-exposure of cells to one of the above-mentioned neuropeptides caused heterologous desensitization, with an observed inhibition of contraction in response to all tested agonists (CCK, 60.3 +/- 5.9%; gastrin-releasing peptide: 56.7 +/- 3. 5%; Substance P, 60.6 +/- 6.5%). A similar decrease was observed in InsP3-induced contractions resulting in a desensitization of the InsP3 response as well. Full recovery of contractile responses appeared within 30 min from the end of preincubation, thus indicating that degradation of membrane receptors did not occur. Although pre-exposure of the cells to protein kinase C inhibitor GF109203X did not modify CCK-induced homologous desensitization, it blocked CCK-induced heterologous desensitization. This study demonstrates that excitatory phospholipase C-coupled enteric neuropeptides induce a time-dependent homologous as well as heterologous desensitization of smooth muscle contraction occurring at receptor and postreceptor levels.

Human circular colonic smooth muscle cells possess active somatostatin receptors

BACKGROUND & AIMS

Somatostatin alters in vivo colonic motility in different species including humans. Few data are available on a cellular basis that could explain the effects of somatostatin on human colon motility. To address these issues we studied the effects of somatostatin on isolated human circular colonic smooth muscle cells to establish whether its actions are directly or neurally mediated.

METHODS

Circular smooth muscle cells were prepared by enzymatic digestion from surgical specimens of human colon (Sigma) and resuspended in HEPES buffer containing protease inhibitors.

RESULTS

Cholecystokinin (1 nM), carbachol (30 nM) and KCl (20 mM) each caused a contraction of 17%, 16.5% and 15%, respectively. 1 microM of either somatostatin-14, somatostatin-28 or SMS 201-995 alone were able to produce a contraction of 5.1%, 5.7%, and 6.8%, respectively. When smooth muscle cells were preincubated with each of the above-mentioned somatostatin analogs, cholecystokinin-mediated contraction was dose-dependently inhibited only in the presence of antiproteases. The half-maximal effective concentration (EC50) for somatostatin-14, somatostatin-28 and SMS 201-995 were similar (3.5, 5.6, 3.2 nM, respectively).

CONCLUSIONS

Somatostatin acts directly on human circular colonic smooth muscle cells through specific somatostatin receptors. SMS 201-995, a somatostatin receptor subtype-2 preferring analogue, shows a high affinity in inhibiting cholecystokinin-mediated contraction, suggesting the presence of somatostatin receptor subtype-2 on human circular colonic smooth muscle cells.

Colonic smooth muscle cells possess a different subtype of somatostatin receptor from gastric smooth muscle cells

Somatostatin (SS) alters colonic motility. To investigate whether SS has a direct effect on colonic smooth muscle cells, we prepared isolated muscle cells from the descending guinea pig colon and compared the effects of SS with those on isolated gastric smooth muscle cells. In gastric cells, SS had no effect on carbachol-induced contraction, whereas in colonic cells it caused inhibition. In colonic muscle cells, SS-28 caused >85% inhibition of contraction by cholecystokinin octapeptide (CCK-8), bombesin, 12-O-tetradecanoylphorbol-13-acetate, and ionomycin, whereas it had no effect on contraction by these agents in gastric cells. In gastric cells, SS inhibited relaxation. Three synthetic SS analogs had different relative affinities for causing effects in gastric and colonic cells. Pertussis toxin inhibited the action of SS-28 in each muscle cell type by 50-75%. SS-28 alone had a small contractile effect on cells from the circular layer of the colon. SS-28 inhibited carbachol-induced contraction in colonic cells from both the longitudinal and circular layers. These results demonstrate that the action of SS differs in colonic and gastric smooth muscle cells. SS inhibits contractants in colonic cells and relaxants in gastric cells. In colonic cells, SS has a weak contractile effect due to an effect on circular muscle cells and an inhibitory effect on cells from both longitudinal and circular layers. A different SS receptor subtype mediates the actions of SS in colonic and gastric muscle cells. In both cell types, the actions of SS are mediated by pertussis toxin-sensitive and -insensitive G proteins.

Modulation of cholecystokinin activity by albumin

We found that a variety of cholecystokinin (CCK) receptor ligands bind to bovine serum albumin (BSA). This binding was rapid, fully reversible, temperature independent, of low affinity, and specific for BSA; it depended on the concentration of BSA, the chemical structure of the ligand, and the chemical composition of the incubation medium. BSA also decreased the binding of 125I-labeled CCK octapeptide (125I-CCK-8) to CCK receptors on pancreatic acini and membranes but increased the potency with which CCK-8 inhibited binding of 125I-CCK-8. These counterintuitive findings appeared to result from BSA altering the affinities of CCK-8 for different affinity states of the pancreatic CCK receptor. An alternate hypothesis is that BSA increased the efficacy of CCK-8 such that it bound to receptors and also caused biochemical changes in other receptors that reduced their ability to bind 125I-CCK-8. BSA enhanced the ability of CCK-8 to stimulate amylase secretion from pancreatic acini and to cause contraction of dispersed gastric smooth muscle cells. Thus, CCK can bind to BSA, and the BSA-CCK complex has substantially different activities from the free, uncomplexed hormone.

Intracavitary cisplatin (CDDP) in the treatment of metastatic pericardial involvement from breast and lung cancer

Seven patients with lung cancer and two with breast cancer developed a symptomatic pericardial effusion and were treated with intrapericardial cisplatin (CDDP). In all of the patients, cytological confirmation of metastatic effusion was achieved. A single cycle with 10 mg of cisplatin diluted in 20 ml of normal saline was administered for five consecutive days via an intrapericardial catheter. Control of recurrent effusions was obtained in eight of the nine patients. No significant side-effects were observed.

Inhibition of IP3 and IP3-dependent Ca2+ mobilization by cyclic nucleotides in isolated gastric muscle cells

The mechanisms by which cAMP and cGMP and agents that stimulate one (isoproterenol and nitroprusside) or both cyclic nucleotides (VIP) decrease cytosolic free Ca2+ ([Ca2+]i) and inhibit contraction were examined in dispersed, intact, and saponin-permeabilized gastric muscle cells. In these cells, the [Ca2+]i transient responsible for initial contraction is mediated by inositol 1,4,5-trisphosphate (IP3)-dependent Ca2+ release (K. N. Bitar, P. G. Bradford, J. W. Putney, Jr., and G. M. Makhlouf, Science Wash. DC 232: 1143-1145, 1986, and J. Biol. Chem. 261: 16591-16596, 1986). In intact muscle cells, dibutyryl cAMP and all three relaxant agents inhibited contraction, [Ca2+]i, and net Ca2+ efflux (i.e., Ca2+ release) in a concentration-dependent fashion. In permeabilized muscle cells, cAMP, cGMP, and all three relaxant agents 1) inhibited cholecystokinin (CCK)-induced IP3 production (maximal 38-48%), 2) inhibited CCK- and IP3-induced Ca2+ efflux (maximal 55-59%) and contraction (maximal 59-66%), and 3) stimulated Ca2+ uptake (maximal 25-30%), in a concentration-dependent fashion. cAMP and cGMP were equipotent inhibitors of IP3 production and of CCK- and IP3-induced Ca2+ efflux and contraction, whereas cGMP was distinctly more potent as a stimulant of Ca2+ uptake. For all functions, maximal effects induced by cAMP and cGMP were similar to those induced by the three relaxant agents. Inhibition of Ca2+ release was the main determinant of inhibition of contraction; stimulation of Ca2+ uptake was relatively minor (< 5% of Ca2+ efflux). Decrease in IP3 production did not contribute to inhibition of Ca2+ efflux and contraction since inhibition of IP3-induced Ca2+ efflux was similar to inhibition of CCK-induced IP3-dependent Ca2+ efflux.(ABSTRACT TRUNCATED AT 250 WORDS)

Different receptors mediate the action of bombesin-related peptides on gastric smooth muscle cells

Recent studies suggest that different subtypes of receptors may mediate the action of various bombesin-related peptides in different tissues. In the present study the ability of bombesin and its structurally related peptides [litorin, gastrin-releasing peptide (GRP), GRP18-27, neuromedin B, [Leu8]litorin, and bombesin nonapeptide BN(6-14)] to interact with smooth muscle cells isolated from guinea pig stomach was investigated. Each peptide induced a specific contractile response with potencies (D50 in pM) of [Leu8]litorin (0.7) greater than bombesin (1.2) greater than litorin (3) greater than neuromedin B (3.5) = GRP (3.8) = GRP18-27 (3.9) greater than BN(6-14) (70.9). The specific bombesin receptor antagonist psi 13,14-bombesin differed in its potency for inhibiting equipotent concentrations of bombesin, GRP, or neuromedin B, was equipotent for bombesin or GRP (IC50 12.7 and 22.1 nM), and was 11 times less potent for neuromedin B (IC50 234.5 nM), suggesting the presence of subtypes of receptors mediating the action of bombesin-related peptides. To further investigate this possibility, a technique of receptor protection that enables selective preservation of one receptor type was used. GRP or bombesin protected completely the response to GRP or bombesin but abolished the subsequent contractile response to neuromedin B. Neuromedin B, instead, protected only the response to neuromedin B. These results demonstrate that gastric smooth muscle cells possess specific receptors that interact with bombesin-related peptides and that two receptor subtypes mediate the contractile response to these peptides: one subtype is selective for bombesin or GRP, the other for neuromedin B.

Pharmacological characterization of [Leu-13-psi-CH2NH-Leu14]-bombesin as a specific bombesin receptor antagonist on isolated smooth muscle cells

Isolated smooth muscle cells from guinea pig stomach were used to study the pharmacological characteristics of a newly synthetized bombesin analog, [Leu13-psi-CH2NH-Leu14]-bombesin (psi 13,14-BN) to function as antagonist of bombesin-induced contractile response. The antagonism caused by this new analog was compared to that obtained with the substance P analog [D-Arg1,D-Pro2,D-Trp7,9,Leu11]Substance P [( APTTL]SP), which has been used until now to characterize bombesin receptors on smooth muscle cells. psi 13,14-BN resulted to be more potent than [APTTL]SP as antagonist of bombesin action on smooth muscle. Comparing the IC50, psi 13,14-BN (IC50 70 nM) was 8 times more potent than [APTTL]SP (IC50 600 nM). In contrast to [APTTL] SP, the action of psi 13,14-BN was shown to be specific toward bombesin receptors in that it does not interfere with receptors for other agents (i.e., cholecystokinin, acetylcholine or substance P). The antagonism induced by both compounds was competitive inasmuch as the slope of the regression lines obtained by Schild plot analysis were not significantly different from the unity. The apparent affinity for the bombesin receptor was 0.8 nM for psi 13,14-BN and 7.8 nM for [APTTL]SP. These results indicate that psi 13,14-BN acts on isolated gastric smooth muscle cells as a competitive bombesin receptor antagonist, with a higher affinity and specificity than the substance P analog used previously.

Functional gradients in muscle cells isolated from gallbladder, cystic duct, and common bile duct

The existence of a gradient inherent to muscle cells of the biliary tract was examined in muscle cells isolated separately from the fundus of the gallbladder, cystic duct, and common bile duct of the dog. Muscle cells, measured in suspension or as single perfused cells, exhibited a proximal-to-distal gradient expressed by the magnitude of response and the sensitivity to hormonal cholecystokinin octapeptide and neural (acetylcholine and methionine-enkephalin) contractile agonists. Measurements in suspensions showed that cells from the fundus 1) were 7-40 times more sensitive to contractile agonists than cells from the cystic duct and 13-200 times more sensitive than cells from the common bile duct and 2) generated greater maximal contraction. The latter was expressed by the ratio of maximal responses (fundus: cystic duct cells, 1.90 +/- 0.12, P less than 0.001; fundus: common bile duct cells, 1.50 +/- 0.07 P less than 0.001), which was independent of sensitivity to agonists. Similar results were obtained in measurements on single cells with respect to relative sensitivity and to ratio of maximal responses (fundus: cystic duct cells, 1.80 +/- 0.08, P less than 0.001; fundus: common bile duct cells, 1.49 +/- 0.06, P less than 0.001). The ratio of responses to low concentrations of agonists was even higher (three- to fourfold), reflecting both the greater sensitivity and the greater contraction of muscle cells of the fundus. We conclude that a proximal-to-distal biliary gradient exists that is an inherent property of muscle cells from various regions of the biliary tract; the gradient would act to facilitate gallbladder emptying in response to hormonal and neural stimulation.

Identification of separate bombesin and substance P receptors on isolated muscle cells from canine gallbladder

Smooth muscle cells were isolated from the dog gallbladder and used to examine whether bombesin-14 and substance P cause direct contraction and whether this effect is mediated by the same or different receptors. Both peptides caused concentration-dependent contraction that was inhibited by two substance P derivatives, [D-Pro2,D-Trp7,9]SP ([PTT]SP) and [D-Arg1,D-Pro2,D-Trp7,9,Leu11]SP ([APTTL]SP). In nonmuscle cells, these substance P derivatives exhibit preferential antagonism of responses to substance P and bombesin, respectively; accordingly, these properties were used to demonstrate the presence of separate bombesin and substance P receptors. Estimates of the apparent Ki showed that [PTT]SP was 40 times more potent than [APTTL]SP as an antagonist of the response to substance P, whereas [APTTL]SP was 85 times more potent than [PTT]SP as an antagonist of the response to bombesin-14. Estimates of median inhibitory concentration obtained from inhibition curves for the effect of various concentrations of each antagonist on the responses to substance P and bombesin-14 confirmed that [PTT]SP was a preferential antagonist of the response to substance P and [APTTL]SP, a preferential antagonist of the response to bombesin-14. The results demonstrate the presence of separate bombesin and substance P receptors mediating contraction of smooth muscle cells of the dog gallbladder.

Characterization of opioid receptors on isolated canine gallbladder smooth muscle cells

Smooth muscle cells were isolated from the fundus of the canine gallbladder and examined for the presence of opioid receptors. The cells contracted in a concentration-dependent manner in response to three opioid peptides (Met-enkephalin, dynorphin1-13 and Leu-enkephalin), which are known derivatives of opioid precursors present in myenteric neurons of the gut. The order of potency was Met-enkephalin greater than dynorphin1-13 greater than Leu-enkephalin. The contractile response to opioid agonists was selectively inhibited by opioid antagonists (naloxone and Mr2266) but not by muscarinic, CCK/gastrin or tachykinin antagonists. Equivalent responses to the three opioid peptides exhibited differential sensitivity to preferential antagonists of mu (naloxone) and kappa (Mr2266) opioid receptors consistent with the presence of the three main types of opioid receptors (mu, delta and kappa) on canine gallbladder muscle cells.

Gastric acid and pancreatic polypeptide responses to modified sham feeding: indication of an increased basal vagal tone in a subgroup of duodenal ulcer patients

The effect of sham feeding upon gastric acid secretion and pancreatic polypeptide release was investigated in 28 patients with duodenal ulcer in order to evaluate whether high basal vagal activity is the cause of basal acid hypersecretion in patients with duodenal ulcer and basal secretion higher than 30% of their peak acid output. The patients were divided into two groups based on the ratio of basal/pentagastrin stimulated peak acid output (BAO/PAO) was higher or lower than 0.30: group A n = 19 (BAO/PAO less than or equal to 0.30) and group B n = 9 (BAO/PAO greater than 0.30). Gastric acid response to sham feeding (SAO) was significantly higher than basal level in group A (SAO: 11.4 mEq/h (2.5-20.1) vs BAO: 5.2 mEq/h (0.8-22.9), p less than 0.01, median (range)) while in group B the acid secretion did not increase with sham feeding (SAO: 9.6 mEq/h (4.5-13.6) vs BAO: 8.8 mEq/h (6.3-13.8) ns, median (range)). A negative correlation (r= -0.6118226, p less than 0.01) was found between acid increase expressed as basal subtracted sham feeding response (SAO-BAO) and BAO/PAO ratio of the entire group of duodenal ulcer patients (n = 28) suggesting that the greater is basal acid secretory capacity the smaller is acid increase in response to residual vagal activation. Pancreatic polypeptide response to sham feeding was higher in group A than in group B but no correlation (r = 0.20, n = 28) nor individual covariation was found between acid and pancreatic polypeptide secretions during vagal stimulation. sham feeding did not change serum gastrin. It is concluded that an increased vagal stimulation seems to be the cause of basal hypersecretion in a subgroup of patients with duodenal ulcer. The lact of correlation between the pancreatic polypeptide and acid responses to vagal stimulation interferes with the reliability of pancreatic polypeptide as indicator of vagal tone on gastric parietal cells.

Evidence that bombesin releases extragastric gastrin in man

Bombesin-induced gastrin release from extragastric sources has been investigated in two groups of patients without gastric antrum: 11 patients with total gastrectomy and 11 patients with subtotal (Billroth II) gastrectomy. A 30-min bombesin infusion (5 ng . kg-1 . min-1) caused a prompt significant gastrin increase (P less than 0.05) in both groups of patients. The gastrin response to bombesin was significantly (P less than 0.005) lower in patients without antral tissue than in the control group (n = 7). The individual peak gastrin responses, in totally (TG) and subtotally (SG) gastrectomized patients, were significantly over basal levels (TG: peak 100.3 +/- 12 vs. basal 62.8 +/- 9.1, P less than 0.005; SG: peak 96.9 +/- 9.4 vs. basal 72.4 +/- 6.8, P less than 0.001; pg/ml, mean +/- S.E.M.). These data indicate that bombesin acts not only on antral G cells, but on all gastrin cells in the gastrointestinal tract.

Bombesin effects on human GI functions

In this article some of the actions of amphibian skin peptide Bombesin (BBS) on human gastrointestinal and pancreatic functions are reviewed. BBS causes increases of lower esophageal sphincter pressure, delay of gastric emptying, inhibition of mechanical activity of duodenum and jejunum and gallbladder emptying. BBS also releases in man gastrin and stimulates gastric acid secretion. BBS administration induces release of insulin, glucagon and pancreatic polypeptide from human Islet of Langerhans and causes secretion of pancreatic bicarbonates and enzymes in duodenal juice and release of pancreatic enzymes in blood stream.

Effect of bombesin on plasma insulin, pancreatic glucagon, and gut glucagon in man

The effect of bombesin on insulin, pancreatic glucagon, and gut glucagon was investigated in eight healthy volunteers and two pancreatectomized patients. Bombesin, infused iv at the constant rate of 5 ng kg-1 min-1, produced a sharp and statistically significant rise in the plasma insulin concentration. The peak was reached at 5 min (26 +/- 2.17 microU/ml; P less than 0.005 vs. basal values), followed by a prolonged and statistically significant (P less than 0.05) decrease in blood glucose. Pancreatic glucagon rapidly rose to a maximal value of 80.5 +/- 7.6 pmol/liter (P less than 0.005 vs. basal values). In contrast with the prompt increase in insulin and glucagon plasma levels, the peak in gut glucagon concentration (55.8 +/- 4.6 pmol/liter; P less than 0.005 vs. basal values) was reached 30 min after bombesin infusion was discontinued. In the two pancreatectomized patients, bombesin induced an increase in gut glucagon concentrations only. The results presented indicate that bombesin acts directly on the A and B cells of the pancreas, influencing glucose homeostasis; however, more complex mechanisms seem to be involved in gut glucagon secretion.