# The contractility of circular and longitudinal intestinal smooth muscle is differentially altered during trinitrobenzenesulfonic acid induced ileitis in guinea pigs

Jean-Pierre Martinolle, Rafael Garcia Villar, Jean Fioramonti, Lionel Bueno

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Jean-Pierre Martinolle, Rafael Garcia Villar, Jean Fioramonti, Lionel Bueno. The contractility of circular and longitudinal intestinal smooth muscle is differentially altered during trinitrobenzenesulfonic acid induced ileitis in guinea pigs. XV Int Symp on Gastrointestinal Motility, Nov 1995, Rome, Italy. 1995. [hal-01600583](https://hal.science/hal-01600583)

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November 5-9, 1995
Hotel Villa Pamphili, Rome

XV INTERNATIONAL SYMPOSIUM
ON
GASTROINTESTINAL MOTILITY

Abstract form

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THE CONTRACTILITY OF CIRCULAR AND LONGITUDINAL INTESTINAL SMOOTH MUSCLE IS DIFFERENTIALLY ALTERED DURING TRINITROBENZENESULFONIC ACID INDUCED ILEITIS IN GUINEA PIGS. J.P. Martinolle, R. Garcia-Villar, J. Fioramonti, L. Buéno. INRA, Department of Pharmacology, BP.3, 31931, Toulouse, France.

Gut inflammation is accompanied by changes in intestinal contractility in both humans and animals. Intrajunal instillation of trinitrobenzenesulfonic acid (TNBS) is an established animal model of chronic ileitis. This study was aimed at determining the effects of TNBS-induced inflammation on the motility of both circular and longitudinal smooth muscle layers of the guinea-pig ileum.

**Methods:** Guinea-pigs given a single intrajunal administration (0.3 ml) of either saline (controls, n=6) or TNBS in 50% ethanol (80 mg/kg, n=6), were sacrificed 6 days later. Ileal strips (longitudinal and circular; 8 x 2 mm) were placed in a superfusion system (Krebs; 37°C; 2 ml/min). Concentration-response curves to carbachol, histamine and adrenaline were constructed (0.1 nM to 0.1 mM). Adrenaline was superfused in a solution containing alprenolol, with either yohimbine or prazosin (all 1 µM). Ileal isometric contractions were recorded and quantified. Maximal effects (Emax) for each agent were expressed in grams over baseline, per mm² of cross-sectional area (mean ± SEM; n=6). Drug potency was expressed as EC50 in µM (mean ± SEM; n=6). Response to KCl (60mM) was taken as a standard control contraction.

**Results:** Longitudinal strips from controls were dose-dependently contracted by carbachol (Emax: 0.49±0.08), histamine (0.34±0.08), adrenaline+yohimbine (0.38±0.06) and adrenaline+prazosin (0.24±0.03). EC50s were 0.23±0.19, 0.73±0.32, 17.2±8.3 and 23.5±12.6, respectively. In longitudinal strips from TNBS-treated animals, Emax for carbachol (0.84±0.11) and histamine (0.65±0.08) were significantly increased (p<0.05) without changes in EC50s (0.11±0.07 and 0.98±0.37). In contrast there were no contractile responses to either α1- or α2-adrenoceptor stimulation by adrenaline solutions. Circular strips from controls were dose-dependently contracted by carbachol (1.09±0.15) and histamine (0.63±0.14) with EC50s of 0.27±0.24 and 0.69±0.41, but never by adrenaline. In circular strips from TNBS-treated animals these Emax were not modified (0.95±0.14 and 0.52±0.09), but EC50s were increased (7.20±2.30 and 7.40±1.87), while adrenaline remained without effect. Moreover, 60 mM KCl-induced contraction was not different in TNBS-treated tissues and in controls, neither in longitudinal nor in circular strips.

**Conclusion:** During TNBS-induced ileitis in guinea-pigs, the in vitro contractile responses of circular and longitudinal smooth muscle to receptor agonists is differentially altered, while nonreceptor-induced KCl contraction is not modified.

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The principal author affirms that the material herein: 1) will not have been published as an article by Nov. 5, 1995 or have been presented at a national meeting of a national society, or abroad at a major foreign or international meeting; 2) that if human subjects were exposed to risks not required by their medical needs, the study was approved by an appropriate committee or, if no such committee was available and informed consent was needed, it was obtained in accordance with the principles enunciated in "The Belmont Report: Ethical Principles and Guidelines for the Protection of Human Subjects of Research", U.S. Government Printing Office: 1983-381-132:3205, or 3) any animal studies conform with the "Guiding Principle in the Care and Use of Animals" of the American Physiological Society.

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A Principal Author's Name R. GARCIA-VILLAR
Address INRA - Department of Pharmacology
BP.3 - 180 Chemin de Tournefeuille
31300 TOULOUSE Cedex - France
Telephone 33 61 28 51 51 Fax 33 61 28 53 10

E. Corazziari, M.D. - Chairman

XV Intl. Symp. on GI Motility
Cattedra di Gastroenterologia I
Clinica Medica II
Università "La Sapienza"
Policlinico Umberto I
Viale del Policlinico
00161 Roma - Italy
Abstracts for the 15th International Symposium
on Gastrointestinal Motility

5-9 NOVEMBER 1995, HOTEL VILLA PAMPHILI, ROME, ITALY

INTERNATIONAL
STEERING
COMMITTEE

Dr E. Corazziari
Chairman, Italy

Dr L. Bueno
France

Dr S. M. Collins
Canada

Dr J. Dent
Australia

Dr N. E. Diamant (Emeritus)
Canada

Dr R. C. Heading
UK

Dr J. Janssens
Belgium

Dr C. Owyang
USA

Dr S. K. Sarna
USA

Dr J. D. Wood
USA

SCIENTIFIC
SECRETARY

Dr E. Corazziari, MD
Cattedra di Gastroenterologia I
Clinica Medica II
Università 'La Sapienza'
Policlinico Umberto I
Viale del Policlinico
00161 Roma
Italy

Tel +39 6 4469965/4452908

Fax +39 6 4469965/4463737

LOCAL SCIENTIFIC
COMMITTEE

Dr F. Baldi
Dr L. Barbara
Dr M. Bortolotti
Dr E. Corazziari
Dr S. Cucchiara
Dr M. Impicciatore
Dr C. Maggi
Dr L. Marzio
Dr S. Faussone-Pellegrini
Dr A. Staiano
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Dr A. Torsoli

LOCAL EXECUTIVE
COMMITTEE

Dr V. Annese
Dr D. Badiali
Dr G. Bassotti
Dr I. Bontempo
Dr M. Cicala
Dr E. Corazziari
Dr F. I. Habib
Dr N. Pallotta
Dr C. Severi
Dr A. Torsoli
## HIGH FAT MEALS: DO THEY REALLY AFFECT THE COMPETENCE OF THE OESOPHAGO-GASTRIC JUNCTION?

M Mangano, A Picone, PA Bianchi, R Penaghi

Cattedra di Gastroenterologia, University of Milan-IRCCS Ospedale Maggiore, Milan, Italy

Although fatty foods are commonly considered detrimental in patients with gastro-oesophageal reflux (GOR) disease there are few and inconclusive data on the effect of fat on GOR and its mechanisms. It has been suggested that fat may provoke reflux by increasing the rate of transient lower oesophageal sphincter relaxations (TLOSRs) and their association with reflux and/or by decreasing basal lower oesophageal sphincter pressure (BLOSP). Aim: To compare the effect of a balanced meal (2500 kJ, 30% fat, 53% carbohydrate, 17% protein) and an equicaloric high fat meal (65% fat) on GOR, TLOSRs and BLOSP in 8 healthy subjects aged 19-30 years (6 men) and in 12 patients with GOR disease (erosive oesophagitis or oesophageal pH<4 for >5% of time) aged 23-57 years (9 men). All subjects and 7 patients were studied in the recumbent and 5 patients in the upright position.

**Methods:** The 2 meals were administered on separate days in randomised order and combined oesophageal pH and motility monitoring (pharynx, oesophageal body, lower oesophageal sphincter with a sleeve, stomach) was performed for a period of 180 min after each meal.

**Results (mean±SE):**

<table><thead><tr><th rowspan="2">Meal type</th><th colspan="2">Healthy subjects</th><th colspan="2">Patients *</th></tr><tr><th>Balanced</th><th>High fat</th><th>Balanced</th><th>High fat</th></tr></thead><tbody><tr><td>% pH&lt;4</td><td>2.7±0.9</td><td>2.6±1.9</td><td>15.4±4.6</td><td>12.9±5.0</td></tr><tr><td>Reflux episodes (no/h)</td><td>1.0±0.4</td><td>1.1±0.7</td><td>5.4±1.2</td><td>4.8±1.3</td></tr><tr><td>TLOSRs (no/h)</td><td>3.7±0.8</td><td>3.9±0.6</td><td>7.2±2.4</td><td>5.8±0.9</td></tr><tr><td>% TLOSR with GOR</td><td>36±11</td><td>28±7</td><td>65±8</td><td>57±8</td></tr><tr><td>BLOSP (mmHg)</td><td>14±3</td><td>12±1</td><td>7±2</td><td>9±2</td></tr></tbody></table>

* Data from recumbent and upright patients were pooled because posture had no influence on results.

**Conclusions:** Doubling the fat content of a meal does not affect postprandial oesophago-gastric competence or GOR for at least 3 hours in either healthy subjects or patients with GOR disease. The possibility remains that fat increases GOR in the late post-prandial period by prolonging the time acidic material persists in the stomach.

## MECHANISMS OF INCREASED GASTRIC EMPTYING BY ERYTHROMYCIN

C. Mathis and C.H. Malbert INRA, Station de Recherches Porcines, 3559 Saint Gilles, L'Hermitage, France

Gastric emptying rate depends on the ratio between propulsive and resistive forces, the later being mainly generated by the pylorus. Yet, increased resistance is supposed to retard gastric emptying, some gastrointestinal compounds such as cisapride also increase pyloric resistance. We have investigated changes in transpyloric flow and pyloric resistance induced by erythromycin (lactobionate, EM) in eight chloralose-urethane anaesthetised pigs. EM (10⁻³M) or saline was infused during 30 min in the gastroepiploic artery cannulated in caudad direction 10 cm before the pylorus. Antropyloroduodenal motility was measured with a sleeve/side holes assembly and transpyloric flow was evaluated with a juxtapyloric flowmeter probe. Increased gastric emptying after EM was the consequence of flow pulses of larger stroke volume (13.7 ± 2.24 vs. 3.6 ± 0.30 ml, p<0.05) and of longer duration (10.9 ± 0.45 vs. 6.9 ± 0.23 s, p<0.05) but occurring at the same frequency (3.9 ± 0.55 vs. 3.2 ± 0.30 per min, p<0.05). Duodeno-gastric backflow that amounted to 9% of forward flow with saline, was absent with EM. Amplitude and frequency of the antropyloroduodenal pressure events were doubled irrespective of the recording site (57.2 ± 4.78 vs. 38.2 ± 2.52 mmHg and 4.3 ± 0.17 vs. 3.0 ± 0.11 per min for the pylorus, p<0.05). They were associated to flow pulses in a 1:1 ratio instead of a 1:2 ratio with saline. EM induced a significant decrease in pyloric resistance that was halved compared to saline (2.3 ± 0.21 vs. 4.6 ± 0.46 mmHg·ml⁻¹ s, p<0.05), a consequence of a reduced time interval between the onset of the pyloric pressure events and the onset of the flow pulses (1.0 ± 0.31 vs. 3.2 ± 0.58 s, p<0.05) rather than decrease in pyloric basal tone that was actually increased by EM (34.1 ± 2.07 vs. 18.2 ± 0.69 mmHg for EM vs. saline). In conclusion, EM increases gastric emptying rate by generating flow pulses of greater stroke volume and of unchanged frequency. The greater stroke volume of the flow pulses originates from a reduced pyloric resistance.

## THE CONTRACTILITY OF CIRCULAR AND LONGITUDINAL INTESTINAL SMOOTH MUSCLE IS Differentially ALTERED DURING TRINITROBENZENESULFONIC ACID INDUCED ILEITIS IN GUINEA PIGS.

J.P. Martinolle, R. Garcia-Villar, J. Fioramonti, L. Buéno. INRA, Department of Pharmacology, BP.3, 31931, Toulouse, France.

Gut inflammation is accompanied by changes in intestinal contractility in both humans and animals. Intrajugalinal instillation of trinitrobenzenesulfonic acid (TNBS) is an established animal model of chronic ileitis. This study was aimed at determining the effects of TNBS-induced inflammation on the motility of both circular and longitudinal smooth muscle layers of the guinea-pig ileum.

**Methods:** Guinea-pigs given a single intrajugalinal administration (0.3 ml) of either saline (controls, n=6) or TNBS in 50% ethanol (80 mg/kg, n=6), were sacrificed 6 days later. Ileal strips (longitudinal and circular; 8 x 2 mm) were placed in a superfusion system (Krebs: 37°C; 2 ml/min). Concentration-response curves to carbachol, histamine and adrenaline were constructed (0.1 nM to 0.1 mM). Adrenaline was superfused in a solution containing alprenolol, with either yohimbine or prazosin (all 1 µM). Ileal isometric contractions were recorded and quantified. Maximal effects (Emax) for each agent were expressed in grams over baseline, per mm² of cross-sectional area (mean ± SEM; n=6). Drug potency was expressed as EC₅₀ in µM (mean ± SEM; n=6). Response to KCl (60mM) was taken as a standard control contraction.

**Results:** Longitudinal strips from controls were dose-dependently contracted by carbachol (Emax: 0.49±0.08), histamine (0.34±0.08), adrenaline+yohimbine (0.38±0.06) and adrenaline+prazosin (0.24±0.03). EC₅₀s were 0.23±0.19, 0.73±0.32, 17.2±8.3 and 23.5±12.6, respectively. In longitudinal strips from TNBS-treated animals, Emax for carbachol (0.84±0.11) and histamine (0.65±0.08) were significantly increased (p<0.05) without changes in EC₅₀s (0.11±0.07 and 0.98±0.37). In contrast there were no contractile responses to either α₁- or α₂-adrenoceptor stimulation by adrenaline solutions. Circular strips from controls were dose-dependently contracted by carbachol (1.09±0.15) and histamine (0.63±0.14) with EC₅₀s of 0.27±0.24 and 0.69±0.41, but never by adrenaline. In circular strips from TNBS-treated animals these Emax were not modified (0.95±0.14 and 0.52±0.09), but EC₅₀s were increased (7.20±2.30 and 7.40±1.87), while adrenaline remained without effect. Moreover, 60 mM KCl-induced contraction was not different in TNBS-treated tissues and in controls, neither in longitudinal nor in circular strips.

**Conclusion:** During TNBS-induced ileitis in guinea-pigs, the in vitro contractile responses of circular and longitudinal smooth muscle to receptor agonists is differentially altered, while nonreceptor-induced KCl contraction is not modified.

## INCREASED GASTRIC EMPTYING RATE BY ERYTHROMYCIN IS VAGALLY MEDIATED

C. Mathis and C.H. Malbert INRA, Station de Recherches Porcines 35590 Saint Gilles, L'Hermitage, France

Motilin receptor density and affinity suggest that erythromycin (EM) stimulates gastric motility and emptying by a combined action on the smooth muscle and myenteric neurones. However, because Motilin receptors have recently been found in the brain and on vagal related structures, the central nervous system might also be involved in EM *in vivo* activity. The possible modulation of EM effects by the vagus has been investigated in eight chloralose-urethane anaesthetised pigs. EM (lactobionate, 10⁻³M) was infused for 30 min in the gastroepiploic artery that was cannulated in caudad direction 10 cm before the pylorus. Reversible interruptions of vagal pathways were performed by repetitive cooling of the cervical vagal trunks at 3°C during EM infusion. Antropyloroduodenal motility was evaluated with a sleeve/side holes assembly and transpyloric flow was measured by a juxtapyloric flowmeter probe. Vagal cooling produced a marked inhibition in EM induced increased gastric emptying (23 ± 1.1 vs. 50 ± 2.6 ml·min⁻¹, p<0.05). Gastric emptying remained pulsatile and the frequency of the flow pulses was unchanged, but their stroke volume was halved (7.8 ± 3.31 vs. 13.7 ± 2.24 ml, p<0.05). This was the consequence of flow pulses of reduced duration (8.1 ± 0.77 vs. 10.9 ± 0.45 s, p<0.05) and of smaller peak flow rate (2.8 ± 0.71 vs. 4.4 ± 0.53 ml·s⁻¹, p<0.05). On the contrary, vagal cooling did not significantly modify the increased frequency and amplitude of the antropyloroduodenal pressure events induced by EM. The decrease emptying rate during vagal cooling was due to a threefold increase in pyloric resistance (6.3 ± 1.98 vs. 2.3 ± 0.21 mmHg·ml⁻¹ s, p<0.05), a consequence of a longer time interval between the onset of pyloric pressure events and transpyloric flow pulses (1.0 ± 0.31 vs. 1.9 ± 0.33 s). It is concluded that (i) EM related increased emptying rate is dependant on the integrity of vagal pathways and (ii) vagally mediated EM effects are directed towards pyloric resistance and not gastric propulsive forces.