Effect of gastric resection, Roux-en-Y diversion and vagotomy on gastric emptying in the rat

The effects of Roux-en-Y limb length on gastric emptying and enterogastric reflux in rats

PURPOSE

To assess the effects of Roux-en-Y jejunal limb length on gastric emptying and enterogastric reflux.

METHODS

Seventy male Wistar rats were submitted to antrectomy with Roux-en-Y reconstruction and then were divided into two groups of 35 animals. Group A, short limb (7.5 cm) and Group B, standard limb (15 cm). Group A and B were subdivided into five subgroups each in order to study enterogastric reflux at 30 and 60 minutes and to evaluate gastric emptying at 5, 10 and 15 minutes. In order to measure gastric emptying and enterogastric reflux, radiotracers 99m Tc-Phytate and 99m Tc-DISIDA were respectively used.

RESULTS

For gastric emptying, the radiotracer concentration was lower in Group A than in Group B after five minutes. The enterogastric reflux was present, but there were no significant differences between enterogastric reflux indexes concerning both A and B Groups.

CONCLUSION

A standard Roux limb, besides being unable to protect the stomach from the enterogastric reflux, may become a functional barrier for gastric emptying.

Is gastrin partially responsible for body weight reduction after gastric bypass?

BACKGROUND

The rationale for bariatric surgery is to reduce food intake by gastric restriction and/or malabsorption by intestinal bypass. Unlike ghrelin, gastrin is released in response to food intake. Here we studied the possible role of gastrin in the reduction of body weight after gastric bypass surgery.

METHODS

Rats were divided into four experimental groups and were subjected to different treatments: sham operation, gastric bypass, sham operation + gastrin infusion, and gastric bypass + gastrin infusion. The gastric bypass was done by anastomosing the esophagus to the duodenal bulb without bypassing the intestine. Gastrin-17 was infused continuously for 2 months via subcutaneously implanted osmotic minipumps. Body weights were recorded; serum gastrin and ghrelin levels were measured, and the stomachs were analyzed morphologically.

RESULTS

Gastric bypass resulted in reducing the body weight, stomach weight, thickness of the oxyntic mucosa, serum gastrin concentration, and activity of the ECL cells. Gastrin infusion prevented mucosal atrophy and ECL cell inactivation, and attenuated the body weight reduction that occurred following gastric bypass. Circulating ghrelin and ghrelin-producing A-like cells in stomachs that had undergone gastric bypass were unchanged with or without gastrin infusion and are thus unlikely to be responsible for the reduced body weight.

CONCLUSION

We suggest that hypogastrinemia and impaired ECL cell function in the oxyntic mucosa of the stomach might be partially responsible for the reduction in body weight that occurs after gastric bypass.

Video-based spatio-temporal maps for analysis of gastric motility in vitro: effects of vagal stimulation in guinea-pigs

Our aim was to evaluate topographically specific gastric motility changes induced by graded vagal activation. A recently developed method of constructing spatio-temporal maps of motility from video movies was adapted to the in vitro perfused guinea-pig stomach with an intact vagal nerve supply. In the unstimulated preparation, spontaneous activity was low or absent. Bilateral vagal stimulation with frequencies as low as 0.2 Hz triggered weak anally, and in some cases orally, propagating antral contractions at rates of about 5-6 min-1. Upon stimulation with higher frequencies, antral contractions increased significantly in length (starting more proximally) and amplitude, and produced large pressure peaks of up to 25 hPa, with maximal effects at 2-4 Hz. In contrast, the speed of propagation and the interval between peristaltic waves did not change with vagal stimulation at any frequency. Vagal stimulation also produced a significant and frequency-dependent enlargement of the fundus with a maximal effect at 4 Hz. It is concluded that a very low tonic vagal activity is apparently necessary and sufficient to express basic antral motility, while more sustained vagal activity is necessary for high-amplitude gastric contractions and significant sustained fundic relaxation. The constant interval between propagating contractions supports the concept that vagal input impinges on intrinsic enteric neural circuits that have a modulatory role in the myogenic mechanism underlying slow-wave peristalsis, rather than directly on gastric musculature.

Esvaziamento gástrico e jejunal proximal em ratos submetidos ou não à gastrectomia parcial com reconstrução do trânsito intestinal em Y de Roux ou a Billroth II

Estudou-se os efeitos da reconstrução gastrojejunal em Y de ROUX (YR) ou a BILLROTH II (BII) no esvaziamento gástrico (EG) e jejunal proximal de líquido nutriente. Constitui-se quatro grupos de dez ratos Wistar machos: simulado (grupo I), antrectomia em YR (grupo II), gastrectomia subtotal em YR (grupo III) e antrectomia a BII (grupo IV). O EG e jejunal proximal foram avaliados no sétimo dia de pós-operatório, 60 minutos após a introdução gástrica de ovo cru mexido marcado com Tc99m. Após esse tempo, retirou-se separadamente o estômago, intestino proximal e restante do intestino, seguindo-se da quantificação do radioisótopo presente em cada segmento, numa câmara de ionização. O EG foi mais rápido nos animais gastrectomizados do que naqueles sem gastrectomia (α < 0,05). O EG no grupo antrectomia em YR foi mais lento do que no grupo gastrectomia subtotal em YR (α < 0,05), mas não apresentou diferença significante com relação ao grupo antrectomia a BII. O esvaziamento da alça de ROUX (grupos TI e III) não mostrou diferença significante em relação ao da alça eferente de igual comprimento (grupo IV). Concluiu-se que o EG de liquido nutriente foi semelhante na antrectomia em YR ou a BII e que nas reconstruções em YR, foi mais rápido na gastrectomia subtotal do que na antrectomia.

Nizatidine accelerates gastric emptying of a solid meal in rats

Nizatidine, a new histamine-2-receptor antagonist, stimulates gastrointestinal motility in dogs and gastric emptying of liquids in rats. Effect of nizatidine on gastric emptying of a solid meal was investigated using a novel gastric emptying model in rats. Male Wistar rats (weighing 200-300 g) were supplied with powdered food containing 30 w/w% barium 14 hr before the beginning of the experiment and x-ray photography of rat stomach was taken under light ether anesthesia. Gastric emptying was assessed by percentage of a decrease in area 30 min after drug was injected intraperitoneally. There was a positive correlation between the area of the gastric outline and the weight of the gastric contents (r = 0.94, P < 0.01). Ether anesthesia itself did not affect gastric emptying. Nizatidine increased gastric emptying dose-dependently (emptied percentage; vehicle: 4.9 +/- 1.5%, 1 mg/kg: 7.2 +/- 0.4%, 3 mg/kg: 10.4 +/- 2.0%, 10 mg/kg: 16.7 +/- 4.9%, 30 mg/kg: 25.7 +/- 7.4%). N-Desmethyl nizatidine (NDM) also stimulated gastric emptying, but nizatidine S-oxide, cimetidine, an famotidine had no significant effects on gastric emptying. Nizatidine and neostigmine, but not NDM, at a subthreshold dose accelerated gastric emptying treated with a low dose of acetylcholine (0.1 mg/kg). Atropine (2 mg/kg, -30 min) did not modulate the gastroprokinetic action of nizatidine, but blocked that of NDM. These findings suggest that this noninvasive method may allow measurement of gastric emptying of solids accurately and that nizatidine and NDM facilitate gastric emptying probably mediated by a direct and/or an indirect (acetylcholinesterase inhibition) cholinergic mechanism.