Nitric oxide has tonic inhibitory effect, but is not involved in the vagal control or VIP effects on motility of the porcine antrum.

BACKGROUND: The involvement of nitric oxide (NO) in vagal control and vasoactive intestinal polypeptide (VIP)-induced effects on antral motility was studied using isolated perfused preparations of porcine gastric antrum with intact vagal innervation. METHODS: The presence of NO and VIP-producing neurons was studied using immunohistochemistry and histochemical techniques. Widespread, but not total, co-localization of NO and VIP immunoreactivity was found in the submucosa and in the muscle layers. RESULTS: Electrical stimulation of the vagus nerves for 5 min (8 Hz, 10 mA, 4 msec) increased the motility index from 2.47 = 0.44 to 11.50 +/- 2.02 (n = 5). This effect was not influenced by the two NO synthase inhibitors N-nitro-L-arginine methyl ester (10(-4) M) and NG-nitro-L-arginine (10(-5) M). However, infusion of inhibitors increased the spontaneous motility index from 2.40 +/- 0.08 to 5.36 +/- 1.08 (P < 0.05) and 3.05 +/- 1.10 to 4.14 +/- 1.04 (P < 0.05), respectively. The addition of L-arginine reversed this effect. Infusion of VIP 2 x 10(-9)M decreased the motility index from 2.32 +/- 0.43 to 1.32 +/- 0.27 (P < 0.05), an effect that was preserved during NO synthase inhibition. Electrical vagus stimulation increased the release of VIP to the venous effluent, an effect that persisted during NO synthase inhibitors. CONCLUSION: We conclude that NO-producing nerves seem to have a tonic inhibitory action on the porcine antral motility, but are not involved in the motor effects of vagal stimulation or VIP infusion.

Effects of topical ropivacaine on eicosanoids and neurotransmitters in the rectum of patients with distal ulcerative colitis.

BACKGROUND: Topical administration of lidocaine has been suggested to have beneficial clinical effects in patients with active ulcerative colitis, but the mechanism of action, if any, remains obscure. As local anaesthetics may exert anti-inflammatory actions through their inhibition of nervous reflexes, we have studied the local effects of a single rectal dose of ropivacaine gel on rectal concentrations of eicosanoids and neurotransmittors in patients with relapsing ulcerative colitis. METHODS: In a randomized, double-blind, placebo-controlled study, concentrations of leukotriene B4, thromboxane B2 and prostaglandin E2 in rectal dialysates and concentrations of substance P, neurokinin A, somatostatin, vasoactive intestinal polypeptide and calcitonin gene-related peptide in rectal biopsies from 19 patients with active, distally located, ulcerative colitis were measured before and after rectal administration of a 200-mg dose of ropivacaine- or placebo-gel by use of radioimmunoassays. For comparison with normal conditions, concentrations of neuropeptides were measured in another 19 patients with relapsing ulcerative colitis and 14 controls with non-inflamed colon. RESULTS: No significant changes in concentrations of eicosanoids or neuropeptides were observed after ropivacaine or placebo administration. Baseline concentrations of all neuropeptides, except somatostatin, were significantly lower in active ulcerative colitis than in controls with non-inflamed colon. CONCLUSIONS: These findings reveal no evidence of anti-inflammatory actions by ropivacaine in active ulcerative colitis and thus provide no rationale for topical treatment with local anaesthetics.

Effect of calcitonin gene-related peptide (CGRP) on motility and on the release of substance P, neurokinin A, somatostatin and gastrin in the isolated perfused porcine antrum.

We studied the effect of porcine CGRP (pCGRP) in concentrations from 10(-10) to 10(-8) mol L(-1) on the motility and on the release of substance P, neurokinin A, somatostatin and gastrin in the antrum using the isolated perfused porcine antrum as experimental model. In addition, we studied the localization of CGRP by immunohistochemistry in the porcine antrum. CGRP-immunoreactive nerve fibres were found mainly in the submucous layer and in the external muscle coat, where they were seen in all layers, and in the ganglia of the myenteric nervous plexus. The frequency of contraction was significantly and dose-dependently increased from a basal level of 11.8 +/- 0.5 contractions per 5 min to 24.4 +/- 3.6 contractions per 5 min at pCGRP 10(-8) mol L(-1). At this dose, the release of substance P and neurokinin A was significantly increased to 470 +/- 149% and 217 +/- 26%, respectively, compared to basal release. The effect of pCGRP was unaffected by the addition of the nonpeptide antagonists for the NK-1 (CP-99994) and NK-2 receptors (SR48968), both at 10(-6) mol L(-1), whereas atropine (10(-6) mol L(-1)) completely abolished the motor effect of pCGRP. The release of somatostatin was significantly increased by 154 +/- 15% in response to CGRP at 10(-8) mol L(-1). The release of gastrin was unaffected by pCGRP. In conclusion, pCGRP increases contractile activity in the porcine antrum, an effect that involves cholinergic mechanisms but is independent of the release of substance P and neurokinin A. in addition, pCGRP increases the release of somatostatin but has no effect on gastrin release in the isolated perfused porcine antrum.

Localisation and neural control of the release of calcitonin gene-related peptide (CGRP) from the isolated perfused porcine ileum.

By immunohistochemistry, CGRP-like immunoreactive (CGRP-LI) nerve fibres were found in the lamina propria along small vessels and in the lamina muscularis mucosae in the porcine ileum. Immunoreactive nerve cell bodies were found in the submucous and myenteric plexus. Upon HPLC-analysis of ileal extracts, CGRP-LI corresponded entirely to porcine CGRP plus smaller amounts of oxidised CGRP. Using isolated vascularly perfused segments of the ileum, we studied the release of CGRP-LI in response to electrical stimulation of the mixed extrinsic periarterial nerves and to infusion of different neuroblockers. In addition, the effect of infusion of capsaicin was studied. The basal output of CGRP-LI was 2.9+/-0.7 pmol/5 min (mean+/-S.D.). Electrical nerve stimulation (8 Hz) significantly increased the release of CGRP-LI to 167+/-16% (mean+/-S.E.M.) of the basal output (n=13). This response was unaffected by the addition of atropine (10(-6) M). Nerve stimulation during infusion of phentolamine (10(-5) M) with and without additional infusion of atropine resulted in a significant further increase in the release of CGRP-LI to 261+/-134% (n=5) and 240+/-80% (n=9), respectively. This response was abolished by infusion of hexamethonium (3x10(-5) M). Infusion of capsaicin (10(-5) M) caused a significant increase in the release of CGRP-LI to 485+/-82% of basal output (n=5). Our results suggest a dual origin of CGRP innervation of the porcine ileum (intrinsic and extrinsic). The intrinsic CGRP neurons receive excitatory input by parasympathetic, possibly vagal, preganglionic fibres, via release of acetylcholine acting on nicotinic receptors. The stimulatory effect of capsaicin suggests that CGRP is also released from extrinsic sensory neurons.

Tachykinins in the porcine pancreas: potent exocrine and endocrine effects via NK-1 receptors.

The localization, release, and effects of substance P and neurokinin A were studied in the porcine pancreas and the localization of substance P immunoreactive nerve fibers was examined by immunohistochemistry. The effects of electrical vagus stimulation and capsaicin infusion on tachykinin release and the effects of substance P and neurokinin A infusion on insulin, glucagon, somatostatin, and exocrine secretion were studied using the isolated perfused porcine pancreas with intact vagal innervation. NK-1 and NK-2 receptor antagonists were used to investigate receptor involvement. Substance P immunoreactive nerve fibers were localized to islets of Langerhans, acini, ducts, and blood vessels. Vagus stimulation had no effect on substance P and neurokinin A release, whereas capsaicin infusion stimulated release of both. Substance P and neurokinin A infusion increased release of insulin, glucagon, and exocrine secretion, whereas somatostatin secretion was unaffected. The effect of substance P on insulin, glucagon, and exocrine secretion was blocked by the NK-1 receptor antagonist. The effect of electrical stimulation of vagus nerves on insulin and exocrine secretion was not influenced by tachykinin receptor antagonists. We conclude that tachykinins stimulate both endocrine and exocrine pancreatic functions through NK-1 receptors. Tachykinins are not involved in vagal regulation of pancreatic secretion in pigs but could constitute part of an alternative stimulatory system.

Fast acting nervous regulation of immunoglobulin A secretion from isolated perfused porcine ileum.

BACKGROUND: The intestinal mucosa harbours a large number of nerve fibres and also plasma cells, providing the anatomical basis for studies of neuroimmune interactions. AIMS: To study the effect of different neurotransmitters and electrical stimulation of the extrinsic intestinal nerves on secretion of immunoglobulin A (IgA). METHODS: IgA was measured, using a specific ELISA, in the luminal and venous effluent from isolated vascularly perfused porcine ileal segments with preserved extrinsic nerve supply. RESULTS: Infusion of several neuropeptides stimulated IgA output. Somatostatin (10(-8) M) stimulated IgA secretion in the luminal effluent from 46.6 (14.3) to 79.3 (19.0) microg/5 min and increased the venous output to 148.3 (23.0)% (n=6) of basal output, whereas noradrenaline (10(-6) M) inhibited the secretion (to 49.2 (6.5)% of basal output, n=6). Electrical stimulation of the mixed extrinsic nerves supplying the intestinal segment had no effect by itself. However, electrical stimulation during infusion of alpha adrenergic blockers or coinfusion of both alpha adrenergic and muscarinic blockers resulted in an immediate and significant increase in IgA, an effect that was abolished by nicotinic blockade. CONCLUSION: The extrinsic nerve supply to the intestine could be involved in fast acting regulation of mucosal immune functions.

Tachykinins stimulate acid and pepsinogen secretion in the isolated porcine stomach.

The precise role of tachykinins in regulation of acid and pepsinogen secretion has not been established. Tachykininergic effects on acid and pepsinogen secretion could be mediated either directly in the proximal stomach or through other indirect mechanisms, i.e. gastrin secretion. We studied the effects of the two tachykinins, substance P and neurokinin A, and of capsaicin, on acid and pepsinogen output, in isolated porcine non-antral stomach preparation. The release of substance P and neurokinin A was studied during electrical stimulation of the vagal nerves, and during capsaicin infusion. Substance P infusion (10-8 M) increased acid secretion from 30 +/- 8 to 68 +/- 17 fmol min-1 (n=6, P < 0.05) and pepsinogen output from 46 +/- 12 to 160 +/- 47 units of pepsin min-1 (n=9, P < 0.05). Neurokinin A also stimulated both acid and pepsinogen secretion, while capsaicin had no effect on either parameter. Electrical stimulation of the vagal nerves increased the release of both peptides. We conclude that tachykinins may be involved in regulation of acid and pepsinogen secretion.

Isolation and molecular characterization of porcine calcitonin gene-related peptide (CGRP) and its endocrine effects in the porcine pancreas.

The aim of this study was to investigate the possible role of porcine calcitonin gene-related peptide (CGRP) in the regulation of the endocrine porcine pancreas. Initially, we isolated and purified CGRP from extracts of porcine adrenal glands and pancreases. A single molecular form of the peptide was found in the two tissues. The adrenal peptide was sequenced and found to differ from human alpha-CGRP at six positions and from human beta-CGRP at three positions. By immunohistochemistry, CGRP was found in nerve fibers in the pancreatic ganglia. A synthetic replica of the porcine peptide was infused at different dose levels (10(-10), 10(-9), and 10(-8) M) into isolated perfused porcine pancreata. With 5 mmol/L glucose in the perfusate. CGRP at 10(-10) and 10(-9) M increased insulin and glucagon secretion, whereas significant decreases were observed with 10(-8) M. Somatostatin secretion was increased significantly by 10(-8) M CGRP. In immunoneutralization studies (n = 6) using a high-affinity somatostatin antibody, the inhibitory effect of CGRP at 10(-8) M was reversed to a significant stimulation of insulin and glucagon secretion. Insulin secretion in response to square-wave increases in glucose concentration to 11 mM was inhibited dose dependently by CGRP; at 10(-8) M the insulin output decreased by 72+/-9% (n = 6). The present results indicate that CGRP may be involved in the regulation of insulin and glucagon secretion from the porcine pancreas.

Tachykinins may mediate capsaicin-induced, but not vagally induced motility in porcine antrum.

Tachykinins are thought to be involved in extrinsic control of motility in the gastrointestinal tract. Using the isolated perfused porcine antrum with intact vagal innervation, we studied the effects of substance P, neurokinin A and capsaicin infusion, and electrical stimulation of the vagus nerves on antral motility without or with infusion of non-peptide antagonists for NK-1 receptors (CP96345) and NK-2 receptors (SR48968). Substance P and neurokinin A stimulated antral motility in a dose-dependent manner. The effect could be inhibited by atropine or a combination of the NK-1 and NK-2 receptor antagonists. Electrical stimulation of the vagus nerves and infusion of capsaicin (10(-5) M) stimulated antral motility. Vagally induced motility was not influenced by infusion of CP96345 and SR48968, whereas the effect of capsaicin was blocked. We conclude that tachykinins may be involved in regulation of antral motility through sensory nerves in the porcine antrum, but they do not seem to be involved in vagal regulation of antral motility.

Calcitonin gene-related peptide (CGRP), a potent regulator of biliary flow.

This study was designed to investigate the effect of porcine calcitonin gene-related peptide (CGRP) on the motility of the porcine biliary tract in vivo. We measured the pressure in the gallbladder and sphincter of Oddi and, in separate experiments, the biliary flow into the duodenum during local intraarterial infusions of CGRP. To determine if the observed effect could be caused by release of cholecystokinin (CCK), we measured the CCK release. The basal pressure in the sphincter of Oddi increased dose-dependently from 5.9 +/- 0.5 mmHg to 11.5 +/- 2.1 mmHg and the motility index of phasic contractions (amplitude x frequency) from 47 +/- 8 to 347 +/- 64 mmHg s-1, at an infusion rate of 32.6 pmol kg-1 min-1. No effect was observed on the gallbladder pressure. CGRP at 6.5 pmol kg-1 min-1 significantly reduced the biliary flow into the duodenum to 47.7 +/- 6% of the basal level. Atropine, injected intravenously, completely abolished the contractile effect of CGRP. CGRP had no effect on the release of CCK. We conclude that CGRP increases biliary motility and hereby reduces bile flow, an effect which involves cholinergic but not cholecystokininergic mechanisms.

Tachykinins mediate vagal inhibition of gastrin secretion in pigs.

BACKGROUND & AIMS: Electrical vagal stimulation activates both stimulatory and inhibitory nerve fibers regulating gastrin release in the porcine antrum. The aim of this study was to examine the role of tachykinins in the inhibitory vagal control of gastrin release in the porcine antrum. METHODS: Tachykinin presence was examined by immunohistochemistry and specific radioimmunoassays. Effects of electrical vagus stimulation and capsaicin infusion on tachykinin, gastrin, and somatostatin release were studied using the isolated perfused porcine antrum with intact vagal innervation. Effects of substance P and neurokinin A on gastrin and somatostatin secretion were investigated using nonpeptide neurokinin 1 and 2 receptor antagonists and somatostatin immunoneutralization. RESULTS: Porcine antrum contained substance P and neurokinin A and did not contain neurokinin B, with immunoreactive nerves situated close to gastrin- and somatostatin-immunoreactive cells. Vagus stimulation released substance P, neurokinin A, gastrin, and somatostatin, whereas capsaicin stimulated only tachykinin release Tachykinin infusions increased somatostatin and decreased gastrin secretion, the latter being unaffected by somatostatin immunoneutralization and both being blocked by a combination of neurokinin 1 and 2 receptor antagonists, which also increased gastrin output during vagal stimulation. CONCLUSIONS: Tachykinins strongly inhibit gastrin and stimulate somatostatin secretion in porcine antrum, and tachykininergic nerves mediate inhibitory vagal regulation of gastrin release.

Calcitonin gene-related peptide (CGRP) in the nipple of the rat mammary gland.

The distribution of nerve fibres immunoreactive to calcitonin gene-related peptide (CGRP) was investigated by immunohistochemistry in nipples and mammary glands from lactating and non-lactating rats and compared to the immunoreactivity of other neuropeptides including substance P (SP), neuropeptide Y (NPY), vasoactive intestinal peptide (VIP) and somatostatin (SOM). The study revealed an extensive innervation of the mammary nipples, in which CGRP-immunoreactive (IR) nerve fibres were abundantly present in the epidermis, dermal connective tissue and intralobular connective tissue of the mammary gland parenchyma. Several of the dermal CGRP-IR fibres seemed to follow blood vessels, or formed "ringlet-like" structures. The latter were mostly observed in the dermal connective tissue of the nipple from the lactating rat and may have a mechanoreceptive function, e.g. for the suckling stimuli. The location of SP-IR appeared to be comparable to CGRP-IR, but in fewer fibres. Dense NPY-IR networks of nerve fibres were closely associated with the fascicles of smooth musculature in the core of the nipple base. In contrast, VIP-IR fibres were only sparsely present, and SOM-IR was not detected in the mammary nipples. The immunoreactive content of CGRP and SP was determined by radioimmunoassays. The total amount of immunoreactive CGRP was significantly higher in the nipples from the pregnant and the lactating rats when compared to SP. The maximum concentration of CGRP (65.9 +/- 4.0 pmol/g) measured in the nipples of the pregnant (day 10) rats exceeded almost ninefold the maximum concentration of SP (7.7 +/- 2.0 pmol/g).(ABSTRACT TRUNCATED AT 250 WORDS)

Sympathoadrenal regulation of adrenal androstenedione release.

The effects of epinephrine and of splanchnic nerve activation on adrenocortical androstenedione release were studied in intact isolated perfused pig adrenals with preserved nerve supply. In addition, long-term effects of epinephrine were characterized in bovine adrenocortical cells in primary culture. To investigate the contact zones of the androgen-producing cells of the zona reticularis with the catecholamine producing cells of the adrenal medulla, cortical cells were immunostained for cytochrome P450 side chain cleavage (P450SCC). Perfusion of the isolated adrenals with epinephrine (10(-7) to 10(-5) M) stimulated androstenedione release in a dose-dependent manner. At a concentration of 10(-6) M, epinephrine provoked an increase to 179.11 +/- 16.14% of basal secretion (p < 0.05). Electrical stimulation of the splanchnic nerves led to an increase to 151.5 +/- 9.24% of basal values (p < 0.05). Epinephrine (10(-6) M) reached 40% and activation of the splanchnic nerves 26% of the stimulatory effect of ACTH at a physiological concentration (10(-10) M). The alpha-agonist phenylephrine had no effect on androstenedione release. In cell cultures, epinephrine stimulated the release of androstenedione in a dose-dependent manner with an ED50 of 0.75 x 10(-6) M. The maximal effect was reached at 10(-5) M with 8.92 +/- 0.66 pmol androstenedione/dish/24 h; the basal secretion was 1.44 +/- 0.54 pmol/dish/24 h. The epinephrine-stimulated androstenedione release was abolished by the beta-adrenergic antagonist propranolol while the alpha-adrenergic antagonist phentolamine had no effect. Immunohistochemical staining of paraffin sections of bovine and porcine adrenals for P450SCC revealed that zona reticularis and zona medullaris are closely interwoven.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of nitric oxide in neurally induced pancreatic exocrine secretion in pigs.

Formation of NO, enzymatically catalyzed by NO synthases in both endothelial cells and autonomic nerves, seems to explain some noncholinergic nonadrenergic tissue reactions. We studied the possible role of NO in vagally induced pancreatic exocrine secretion using isolated perfused porcine pancreas (n = 11) with intact vagus nerve (VN) supply. Electrical stimulation of the VN (8 Hz, 10 mA) and infusions of vasoactive intestinal polypeptide (VIP, 2 x 10(-9) M) were carried out before and after addition to the perfusate of the NO synthase inhibitors N omega-nitro-L-arginine methyl ester (L-NAME, 10(-4) M) or NG-nitro-L-arginine (L-NNA, 10(-5) M) with and without further addition of L-arginine (10(-3) M). We also studied the effects of L-arginine alone and of sodium nitroprusside (10(-4) M). In all experiments VN and VIP caused a profuse exocrine secretion (43 +/- 7 and 44 +/- 11 times basal secretion). The inhibitors increased vascular resistance approximately twofold but had no effect on the vascular relaxation caused by VIP and VN. The exocrine fluid response to VN was reduced to 19 +/- 5 and 4.7 +/- 1.8% (L-NAME and L-NNA), and response to VIP was reduced to 54 +/- 12 and 35 +/- 13%. Protein and bicarbonate outputs largely paralleled flow rate. Addition of L-arginine (no effects alone) to L-NAME restored the responses to VN (to 100 +/- 21% of controls) and increased VIP responses (to 65 +/- 11%).(ABSTRACT TRUNCATED AT 250 WORDS)

Pigs produce only a single form of CGRP, part of which is processed to N- and C-terminal fragments.

Using radioimmunoassays with two different antisera, one directed towards the C-terminal and one towards the mid part of porcine and human alpha-CGRP, respectively, we isolated three immunoreactive peptides from acid/ethanol extracts of porcine spinal cord by means of HPLC. By amino acid sequence analysis and mass spectrometry (PDMS), the most abundant peptide was found to be identical to the 37 residue CGRP previously isolated from porcine adrenal glands and spinal cord. The two remaining peptides were identified as pCGRP(18-37) and pCGRP(19-37). Furthermore, the oxidized forms (oxidized Met in position 22) of all three peptides were isolated. We extracted a large amount of tissue and the extractable peptides were purified without discarding side fractions. The purification steps were monitored by immunochemical methods that are highly sensitive for human alpha- and beta-CGRP. Yet we were unable to detect any second full-length form of CGRP. Thus, we conclude that only a single form of full-length CGRP is found in pigs and that this peptide may be cleaved to produce potentially bioactive N- and C-terminal fragments.

Release of immunoreactive somatostatin, vasoactive intestinal polypeptide (VIP), and galanin during propulsive complexes in isolated pig ileum.

We studied the release of immunoreactive somatostatin, VIP, and galanin during net aboral propulsive complexes (NAP) in isolated, perfused, 80-cm segments of porcine ileum. Net aboral propulsive complexes were induced by controlled infusion of liquid (perfusion medium, 3.5 ml/min) into the proximal opening of the ileum segment. In response to liquid infusion, the ileum segments generated propulsive complexes rapidly propagating along the entire segment in the aboral direction, resulting in emptying of the luminal contents. The NAPs occurred with an average interval of 7 minutes. The concentrations of galanin, somatostatin, and VIP in the venous effluent, which in control experiments without luminal infusion did not change, increased significantly (by 63.6 +/- 23.7%, 43.8 +/- 31.8%, and 38.8 +/- 14.6%, respectively) during NAPs and emptying. Atropine (10(-6) mol/l) and hexamethonium (10(-5) mol/l) abolished both NAP generation and peptide responses. It is concluded that the enteric neuropeptides, somatostatin, VIP, and galanin, all of which have pronounced intestinal motor effects, may participate in the generation of net aboral propulsive complexes in the ileum of the pig, possibly mainly in descending relaxation.

Regulation of secretion of pancreatic spasmolytic polypeptide from porcine pancreas.

We studied the neural and hormonal regulation of the secretion of pancreatic spasmolytic polypeptide (PSP), a potential growth factor, from isolated perfused porcine pancreas and the pancreatic exocrine secretion of PSP in response to a meal in young conscious pigs. PSP concentrations in the pancreatic juice ranged from 1 to 180 micrograms/ml. PSP released to the venous effluent amounted to 0.4-7% of the total output. Thus PSP is predominantly an exocrine product. Electrical vagal nerve stimulation increased PSP output 30-fold. Acetylcholine mimicked the effect of nerve stimulation, which was inhibited but not abolished by atropine. Both vasoactive intestinal polypeptide and gastrin-releasing peptide stimulated PSP secretion. PSP concentration in the juice decreased in response to secretin and increased after cholecystokinin octapeptide (CCK-8), but both increased PSP output. In conscious pigs, pancreatic secretion of protein and PSP increased in parallel. Like pancreatic enzyme secretion, we conclude that PSP secretion is controlled by parasympathetic mechanisms that include both cholinergic and peptidergic pathways and by endocrine mechanisms that may include both secretin and CCK-8.

Effect of intestinal inhibitory peptides on vagally induced secretion from isolated perfused porcine pancreas.

Several gastrointestinal peptides inhibit pancreatic secretion in intact animals, but fail to do so in isolated pancreas preparations. Using isolated perfused porcine pancreas with intact innervation, we studied the influence of such peptides (somatostatin, peptide YY, glucagon-like peptide-1, oxyntomodulin, neuropeptide Y, galanin, and calcitonin gene-related peptide) on vagally induced secretion and on release of vasoactive intestinal polypeptide (VIP), a neuropeptide involved in fluid and bicarbonate secretion. In control experiments electrical vagus stimulation increased flow of juice from 0.9 +/- 0.1 to 37.3 +/- 5.6 ml/h and protein output from 43 +/- 5 to 1,244 +/- 336 mg/h (mean +/- SD). With somatostatin-14 at 10(-10) mol/L, the fluid response was reduced to 64 +/- 11% of controls, protein concentration to 78 +/- 3.8%, and protein output to 50 +/- 5% (p < 0.05). At 10(-8) M the response was almost abolished. VIP release, which in control experiments increased from 0.2 +/- 0.05 to 2.1 +/- 0.4 pmol/min, was similarly reduced (p < 0.01). Galanin at 10(-8) M inhibited the fluid response to 54 +/- 7% of controls, protein output to 51.7 +/- 11%, and VIP release to 54 +/- 6% (p < 0.01). None of the other inhibitory peptides affected vagus responses. It is concluded that somatostatin and galanin inhibit pancreatic secretion through interaction with intrapancreatic ganglia. The other peptides act on extrapancreatic, possibly central sites.

Somatostatin restraint of gastrin secretion in pigs revealed by monoclonal antibody immunoneutralization.

We studied the functional coupling between antral somatostatin and gastrin cells in isolated perfused porcine antrum using immunoneutralization with monoclonal antibodies against somatostatin. Their binding affinity was 10(11) l/mol, and the final binding capacity was 11.7 nmol/ml. Antibody infusion within 1 min increased gastrin secretion, reaching a rate of 349 +/- 64% (means +/- SE, n = 7) of basal secretion (59 +/- 5 pmol/l) after 5 min. The effect of somatostatin at 10(-9) mol/l, which inhibited gastrin secretion from 58 +/- 11 to 14 +/- 3 pmol/min (n = 4), was abolished by antibody infusion. Electrical stimulation of the vagus nerves (n = 7) performed during antibody infusion increased gastrin secretion from 224 +/- 61 to 328 +/- 55 pmol/min, not significantly different from the increase in control experiments from 43 +/- 9 to 118 +/- 20 pmol/min, indicating that the vagal stimulation of gastrin secretion does not depend on mechanisms involving somatostatin. We conclude that paracrine antral somatostatin secretion is one of the most important factors regulating basal gastrin secretion in pigs.

Immunohistochemical localization of pancreatic spasmolytic polypeptide (PSP) in the pig.

Pancreatic spasmolytic polypeptide (PSP) is a peptide that is isolated from the porcine pancreas and that affects intestinal motility and growth of intestinal tumour cells in vitro. The peptide was recently demonstrated to be present in large amounts in pancreatic juice. The cellular origin of the peptide, however, is largely unclarified and the localization was therefore studied of PSP in pigs using immunohistochemistry. Positive immunoreactions were seen in the pancreas, the stomach, the duodenum, the jejunum and the ileum. In the pancreas, the PSP immunoreaction was seen in all acinar cells; no immunoreaction was seen in the endocrine islets. In the stomach, it was localized to the mucous cells of the glands in the cardiac gland region, the corpus and the pylorus. In the duodenum a strong immunoreaction was present in Brunner's glands and in the cells of their excretory ducts. In the jejunum and ileum, PSP immunoreactivity was seen in some of the cells in the epithelium of the crypts of Lieberkühn. A peptide chromatographically identical to highly purified PSP was identified in pancreas and stomach extracts. Thus epithelial cells in all parts of the stomach and small intestine contribute to the supply of PSP to the gut lumen.