Effects of enteral feedback inhibition on motility,luminal flow,and absorption of nutrients in proximal gut of minipigs

We wanted to clarify whether the postprandial intestinal feedback control activated by nutrients in the distal gut exerts different effects on motility, transit of digesta, and absorption of nutrients in the proximal gut. Additionally, interrelationships among motility, transit, and absorption were to be elucidated because these relationships have only been investigated in the fasted state. In five minipigs, a 150-cm segment of the proximal jejunum was isolated by two cannulas. Motility of the jejunal segment was recorded by multiple strain gauges and analyzed by computerized methods. Markers (Cr- and Cu-EDTA) were used for the measurement of the flow rate, transit time, and absorption of nutrients. After a meal, the test segment was perfused with 2 kcal/min of an elemental diet over a period of 90 min. A feedback inhibition was activated by infusion of nutrients into the midgut at rates of 1–4 kcal/min. Saline was infused as control. With increasing energy loads infused into the midgut, the motility index and the length of contraction waves decreased, whereas the incidence of stationary contractions increased, ie, the motility changed from a propulsive to a segmenting pattern. These modulations of motility were associated with a linear decrease in the flow rate and a linear increase in transit time. Flow and transit were linearly correlated with each other. Additionally, the reduction in flow rate and the delay in luminal transit were associated with a linear increase in the absorption of nutrients. However, the increase in absorption induced by the feedback mechanism was small (7.3–13.4%) compared to the marked inhibition of the motility parameters (54–64%), the flow rate (59%), and the delay of transit (5.8-fold). Feedback control primarily modulated motor patterns and luminal flow, whereas the small increase in absorption was only a side effect due to the longer contact time of the nutrients with the mucosa.The study was supported by the Deutsche Forschungsgemeinschaft, grant Eh 64/6-3.     

5-Hydroxytryptophan and cisapride stimulate propulsive jejunal motility and transit of chyme in dogs

We investigated in conscious dogs the effects of intravenously administered 5-hydroxytryptophan (5-HTP) and cisapride on the postprandial jejunal mechanical activity by means of six closely spaced extraluminal strain gauge transducers. Drugs were given after administration of a nutrient meal. 5-HTP was given additionally after the administration of a noncaloric cellulose meal. Computer assistance was used to determine the temporal and spatial relationship of contractions and thereby to evaluate the length of spread of contractile waves. Both substances increased the propulsive activity, the contractile force and the motility index and fastened the transit rate of digesta. 5-HTP exhibited the most potent effect when given after administration of the nutrient meal.     

Gastrointestinal motility and gastric emptying after Billroth II gastrectomy in dogs

This study was undertaken to compare the effects of subtotal Billroth II gastrectomy on gastric emptying and gastrointestinal motility with previously published results in intact dogs and in dogs with subtotal Roux-Y gastrectomy. Extraluminal strain gauge transducers were used to study gastrointestinal motility after Billroth II gastrectomy in four conscious dogs. Gastric emptying was measured radiographically. In Billroth II dogs gastric emptying of low-viscosity meals was biphasic with an initial rapid emptying. The addition of nutrients to low-viscosity meals delayed gastric emptying accompanied with reduction in gastric and jejunal motility. Similar to that in Roux-Y dogs, gastric emptying of noncaloric medium-viscosity meals was delayed because of segmenting motor patterns of the jejunal loops, in contrast to the propulsive jejunal motor pattern in intact dogs. Nutrients added to medium-viscosity meals did not change the jejunal motor pattern; gastric emptying was delayed compared with intact dogs. Results show that meal viscosity and jejunal motor pattern influence gastric emptying after Billroth II gastrectomy.This study was supported by the Deutsche Forschungsgemeinschaft, grant Eh 64/3-2.     

Neurotensin slows gastric emptying by a transient inhibition of gastric and a prolonged inhibition of duodenal motility

The effect of neurotensin (10 pmol/kg/min) on gastric emptying was investigated in 5 dogs. Gastroduodenal motility was recorded with strain-gauge transducers and induction coils, gastric emptying was measured radiographically. In the first 15 min, neurotensin abolished gastric emptying, reduced antral and duodenal contractions and diminished the pyloric opening and the duodenal lumen. Subsequently, antral and pyloric activity returned to control values. The emptying rate remained diminished due to segmenting contractions and a small lumen of the duodenum. Results suggest that neurotensin influences gastric emptying mainly by its long-lasting action on the duodenum.     

Ein einfaches Gerät zur induktiven Messung der Darmmotilität mit implantierten Spulen

Zusammenfassung Es wird ein einfaches Gerät beschrieben, mit dem bei Versuchstieren der Durchmesser des Darmes und seine zeitlichen Veränderungen bei der Darmmotorik gemessen werden können. Den Tieren werden Induktionsspulen an einander gegenüberliegenden Stellen des Darmes implantiert. Die Methode ermöglicht wiederholte Messungen über Tage bzw. Wochen unter physiologischen Bedingungen. Die Induktionsspulen werden im allgemeinen in Kombination mit Dehnungsmeßstreifen angewandt. Die Induktionsspulen haben den Vorteil, daß sie während der Versuche leicht geeicht werden können.

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Summary A simple instrument is described which can be used for measurements of the diameter of the intestine and its temporary changes due to motility. The experimental animals have to be provided with implanted induction coils. Later on the recordings can be made under physiological conditions over long periods of time. The induction coils are usually used in combination with strain gages. The induction coils have the advantage of easily being calibrated during the experiments.

     

Pharmacology of a gut motility stimulating enkephalin analogue

The enkephalin analogue pentapeptide Hoe 825 (Tyr-D-Lys-Gly-Phe-L-homocysteine-thiolactone) is a mixed mu/delta opiate agonist. The peptide stimulated interdigestive gut motility at all parts of the intestine in conscious and anaesthetized animals. In dogs digestive motility, measuring mechanical activity, was stimulated with respect to segmental and propulsive properties. The canine uterus was sensitive to the enkephalin. Hoe 825 acts by i.v. or s.c. application, whereas the latter increases the duration of action significantly. The compound's effect can be blocked by naloxone indicating a receptor mediated action, which is localised peripherally. The compound is devoid of a dependence risk, because it does not penetrate into the CNS. At therapeutic doses (in the dog 0.5-2 micrograms/kg i.v.) the compound does not affect cardiovascular, renal or endocrine functions and was without effect on serum blood glucose levels in rats and rabbits.     

Effects of nutrients on gastrointestinal motility and gastric emptying after Billroth-I gastrectomy in dogs

We wanted to clarify the way in which nutrients influence gastrointestinal motility and gastric emptying following distal gastrectomy with Billroth-I gastroduodenostomy. Four gastrectomized dogs were equipped with extraluminal strain gauge transducers. Gastric emptying was measured radiographically. Four intact dogs were used as controls for emptying studies. Following gastrectomy, gastric emptying of both acaloric and nutrient meals was rapid in the initial period of the experiments. Gastric outflow was supported by propagating duodenal contractions. Compared with control dogs, the early emptying of nutrient meals was accelerated. In the following period, nutrients markedly slowed gastric emptying compared with acaloric meals due to a segmenting contractile pattern of the duodenum and a significant diminution of gastrointestinal motility. Results suggest that after Billroth-I gastrectomy (1) the control of gastric emptying by nutrients acts too late to slow the initial enhanced gastric outflow, and (2) the duodenal contractile patterns influence gastric emptying.The study was supported by the Deutsche Forschungsgemeinschaft, grant Eh 64/3-1.