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We compared the stress-strain distributions obtained from isolated segments of the guinea pig duodenum, jejunum, and distal ileum, and the relation between the elastic properties and the collagen content. The segments were immersed in Krebs-Ringer solution containing 10(-2) M MgCl2 to abolish contractile activity. Stepwise inflation of an intraluminal balloon in which the cross-sectional area (CSA) was measured provided the luminal pressure-loading stimulus. The wall thickness was measured by means of 20-MHz A-mode ultrasound. The stress-strain and the incremental elastic modulus-strain distributions were derived from the steady-state values of wall thickness, internal radius, and applied pressure. The CSA-pressure relations and the wall thickness-pressure relations were nonlinear and both differed between the segments (P < 0.01). The stress-strain distributions showed an exponential behavior that fitted well to the equation Y = a x Exp(b x X) (r2 = 0.97 +/- 0.01). The intercept with they axis (a) and the slope of the curves (b) differed between the segments (P < 0.01 and P < 0.05). The collagen contents were 3.99 +/- 0.18 microg/mg, 2.51 +/- 0.13 microg/mg, and 2.10 +/- 0.11 microg/mg in the duodenum, jejunum, and distal ileum, respectively. This difference was significant among all three locations (P > 0.05). An association was found between the collagen content and the incremental elastic modulus (stiffness) at a stress level of 70 kPa (P < 0.05).

The aim was to develop a method for the quantification of the stress-strain distribution of tubular organs in vivo using the porcine duodenum as an experimental model. We placed four electrodes for impedance planimetry and a 20 MHz ultrasound transducer inside an inflatable balloon mounted on a 6 mm-diameter probe for intraluminal use. By means of the ultrasound transducer and the impedance planimetric system, we measured the wall thickness and luminal cross-sectional area of the duodenum. We calculated the luminal radius on the basis of the latter. We validated ultrasonic measurements of wall thicknesses by comparing the former to microscopic measurements of the wall thickness of unstrained duodenal specimens in vitro. Also, we tested whether the magnitude of the applied balloon pressure affected ultrasonic measurements in vitro. The luminal and the outer radius increased non-linearly by a factor of three, rising steeply at low balloon pressures, moderately at higher pressures. The wall thickness decreased as an almost linear function of the applied balloon pressure, resulting in a 50% decrease. The stress-strain distribution calculated on the basis of the balloon pressures, the wall thicknesses and the luminal radii were non-linear. The wall reached a maximum circumferential strain of 1.71 at 6 kPa, corresponding to a stress of 64.8 kPa. Our system enabled us to quantify the stress-strain distribution of the porcine duodenum in vivo, and it may become a valuable tool for future biomechanical investigations of tubular organs in health and disease.

The aim was to study and compare the passive biomechanical wall properties in the isolated duodenum and distal ileum of the guinea pig in vitro. The organ bath contained a Krebs-Ringer solution with 10(-2) M MgCl2 to abolish smooth muscle contractile activity. Stepwise inflation of an intraluminal balloon, in which the cross-sectional area (CSA) was measured, provided the distension stimulus. The circumferential wall tension-strain distributions and wall stiffness-strain relations were computed from steady-state values of these measurements in order to evaluate the passive elastic properties. The CSA always reached equilibrium within the 2-min distension period. The CSAs obtained in the distal ileum were higher than those in the duodenum (P < 0.001). The basal CSA was 17.31 +/- 1.14 mm2 and 12.96 +/- 0.42 mm2 for the distal ileum and the duodenum, respectively (P < 0.01). At a maximum pressure of 6 kPa, the CSA of the ileum was 56.63 +/- 1.81 mm2 and 36.86 +/- 1.76 mm2 for the duodenum (P < 0.01). The circumferential wall tension-strain distributions showed an exponential behavior that accorded well with the equation Y = exp(a+bX) with determination coefficients of 0.96 +/- 0.01 and 0.99 +/- 0.00 in the duodenal segments in the distal ileal segments, respectively. The values of a (intercept with the y-axis) were 0.54 +/- 0.11 and -0.35 +/- 0.19 for the duodenal and ileal segments, respectively (P < 0.001). The slope of the curves (b values) were 4.34 +/- 0.35 in the duodenal and 5.23 +/- 0.37 in the ileal segments (0.1 > P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The aims of the study were to evaluate characteristics of spontaneous motility and of the ascending excitatory peristaltic reflex (AEPR) and intraluminal cross-sectional area in the isolated perfused porcine duodenum. The parameters were measured by an intraluminal catheter by use of the perfused side-hole technique and impedance planimetry. Respiratory parameters such as pH and oxygen consumption and the arterial perfusion pressure were monitored and did not vary significantly throughout the study time. Spontaneous motility was intense at the beginning but declined and disappeared within 45-90 min. It was abolished by atropine, epinephrine, and UK-14,304 (an alpha 2-adrenoceptor agonist). Secondary motility was evoked by intraluminal balloon distensions by raising the balloon pressure to 1.5 kPa for 1-min periods. Reproducible results regarding the AEPR, external balloon diameters to elicit the AEPR, and intraluminal cross-sectional area were obtained. The order of potency (pD2 values) for inhibition of the AEPR was the selective M3-receptor antagonist 4-DAMP greater than atropine greater than the selective M2-receptor antagonist AFDX-116 greater than the selective M1-receptor antagonist pirenzepine greater than hexamethonium. 4-DAMP was 16 and 29 times more potent than AFDX-116 (P less than 0.02) and pirenzepine (P less than 0.02). None of the drugs altered the intraluminal cross-sectional area during the balloon distensions. The model provides the opportunity for physiological and pharmacological studies of duodenal motility and duodenal cross-sectional area devoid of extrinsic neural and endocrine effects. The abolishment of the AEPR by atropine is caused by blockade of the M3-receptor in the porcine duodenum.

The influence of neurotransmitters on gastrointestinal motility is different in different segments of the gastrointestinal tract. To clarify the regulation of duodenal motility, the aim of the present study was to investigate the effects of alpha-adrenoceptor agonism and blockade and of galanin on duodenal motility. The study was undertaken in the isolated perfused porcine pancreatico-duodenal block. The agents under investigation were administered arterially. Duodenal motility was measured by means of a low-compliance perfusion system using an intraluminal catheter. In addition the concentration of galanin was measured in the portal effluent. We found that spontaneous motility was abolished by noradrenaline by an effect that was counteracted by the alpha 2-adrenoceptor antagonist idazoxan. In contrast, the selective alpha 1-adrenoceptor antagonist prazosin did not influence the effect of noradrenaline. Galanin, like noradrenaline, abolished duodenal motility. Furthermore, the concentration of galanin in the portal effluent was decreased by noradrenaline by an alpha 2-adrenoceptor mediated mechanism. We conclude that alpha 2-adrenoceptor activation and galanin inhibit duodenal motility and that the release of galanin from the pancreatico-duodenal preparation is reduced by alpha 2-adrenoceptors.

1. A method for the isolation and vascular perfusion of the porcine pancreas and duodenum was developed. 2. The oxygen consumption of the whole preparation was similar to that of the pancreas alone, and since the duodenal arteriovenous oxygen deficit was similar to that of the total preparation, it was concluded that the duodenum respired adequately. 3. The duodenum rapidly absorbed luminally administered radioactive glucose, and this absorption was strongly inhibited by ouabain and phloridzin. 4. The duodenum secreted secretin rapidly in response to hydrochloric acid, but did not respond to any other luminal stimuli, including lipids, proteins, carbohydrates and bile. Neither was secretin release stimulated by intra-arterially injected acetylcholine. 5. By gel permeation chromatography the release immunoreactive secretin behaved identically to pure natural secretin, indicating that the tissue form and the circulating form have identical molecular size. 6. It is concluded that this model offers an unique opportunity to study the endocrine secretion of the duodenum.

Reports on increased duodenal ulceration after bile diversion prompted the present investigation of gastric acid secretion and gastrin in 16 patients with a Roux-en-Y hepaticojejunostomy and 11 patients with a choledochoduodenostomy. Basal and pentagastrin stimulated acid output, gastrin in serum and gastrin in the antral mucosa were all significantly elevated in patients with a Roux-en-Y compared with those patients having a choledochoduodenostomy. In patients with a Roux-en-Y, bile bypassed the duodenum and the most proximal part of the jejunum; it is hypothesized that the bypass of bile may induce gastric acid hypersecretion secondary to an altered biosynthesis and release of gastrin.

Using sequence-specific radioimmunoassays, the quantities and molecular nature of cholecystokinin (CCK) have been determined in extracts of porcine duodenal mucosa and in the vascular perfusate from the isolated porcine duodenum. The basal concentration of CCK in the perfusate was 84 pM equiv. CCK-8 (mean; range: 32-173 pM, n = 5). After intraluminal stimulation with amino acids, acidified fat emulsions and hydrochloric acid, the concentrations increased 2--5-fold. Both in the basal and stimulated state the concentrations of the related hormone, gastrin, were below 5 pM equiv. gastrin-17. CCK in the perfusate was concentrated by affinity-chromatography using antibodies directed against the bioactive C-terminus. Subsequent gel chromatography revealed a form with a size like or slightly larger than the C-terminal dodecapeptide (CCK-12), a predominant form resembling the C-terminal octapeptide (CCK-8), and a form resembling the C terminal tetrapeptide (CCK-4). The duodenal mucosa contained in addition CCK-33, -39 and CCK-peptides with further N-terminal extensions. The results suggest that small CCK peptides are the principal circulating forms, while CCK-33 and larger forms are biosynthetic precursors.