Alterations in secretory patterns following antrectomy in rats with Pavlov pouches

Importance of the stomach in maintaining calcium homoeostasis in the rat

The stomach helps to maintain calcium homoeostasis by making dietary calcium accessible for uptake in the intestines, although the effect of the stomach on calcium homoeostasis is poorly understood. We examined the effect on blood calcium of gastric surgery in the rat. Within three weeks gastrectomy and fundectomy (excision of the acid producing part of the stomach) induced a slight lowering of the blood calcium concentration. When parathyroidectomy was combined with either gastrectomy or fundectomy the blood calcium concentrations promptly dropped to values lower than after parathyroidectomy alone. The mortality was close to 100% during the first three weeks after combined parathyroidectomy and gastric surgery. It was nil in rats subjected to parathyroidectomy alone. Gastrectomised rats absorbed Ca2+ better than unoperated control rats, possibly reflecting the fact that the serum 1,25-dihydroxyvitamin D concentration was raised. Gastrectomised rats had a food intake that was about 70% of that in intact rats, and the amount of dietary calcium absorbed (net absorption per kg body weight) by the gastrectomised rats was approximately 65% of that in intact control rats. We conclude that the acid producing part of the stomach is important for calcium homoeostasis, since its removal induced lethal hypocalcaemia in parathyroidectomised rats. One possible explanation for the hypocalcaemia induced by gastrectomy is a progressive calcium deficit. In addition, the loss of calciotrophic hormones originating in the stomach may contribute.

Effect of gastrin monoclonal antibody 28.2 on acid response to chemical vagal stimulation in rats

The role of gastrin in mediating the acid response to chemical vagal stimulation was evaluated by intravenous injection of the gastrin monoclonal antibody 28.2 (2.6 mg/rat). The antibody was injected 30 min prior to the administration of vagal stimulants in urethane-anesthetized rats equipped with a double lumen gastric cannula. The gastrin monoclonal antibody 28.2 prevented gastrin-17- but not carbachol-stimulated gastric acid secretion. The gastric acid response to vagal stimulation produced by thyrotrophin-releasing hormone (TRH) injected into the cisterna magna or the dorsal vagal complex and by the GABAB agonist, baclofen, infused intravenously was reduced by 33, 22 and 33% respectively in rats administered with gastrin monoclonal antibody 28.2. These immunoneutralization studies provide evidence that approximately 75% of the acid response to vagal stimulation is not mediated by gastrin in urethane-anesthetized rats.

Insulin-induced gastric ulcers in the rat

Low doses of insulin (less than 1.25 IU/kg body weight) stimulate gastric acid secretion in the rat, whereas higher doses (greater than 2.5 IU/kg) release gastrin and cause gastric ulcers but do not increase acid secretion. In this study we have characterized the ulcerogenic properties of insulin in the rat. A dose of 5 IU/kg subcutaneously proved to be maximally effective. Ulcer formation was rapid, and the maximum 90% incidence was reached after 5 h. Both glucose administration and food intake protected against the ulcerogenic effects of insulin. The effects of anti-ulcer drugs and of vagotomy on insulin-induced ulcers were also studied. Animals were divided into seven groups: 1) saline, 2) omeprazole, 3) ranitidine, 4) sucralfate, 5) bilateral vagotomy, 6) unilateral vagotomy, and 7) antrectomy. Medical treatment was continued for 6 days before insulin administration, operations having been performed 6-8 weeks earlier. Insulin was injected subcutaneously in a dose of 5 IU/kg. Five hours later stomachs were inspected for ulcers. Neither the antrectomized rats nor those treated with omeprazole or ranitidine had ulcers. In the saline- and the sucralfate-treated groups the gastric ulcer incidence was 83% and 80%, respectively, with a mean of six and seven ulcers per rat. Ulcers were evenly distributed between the two sides of the stomach. Rats that had undergone bilateral vagotomy (which abolishes gastric acid secretion and causes hypergastrinemia) responded to insulin with an ulcer incidence of 5%. In the unilaterally vagotomized rats there were only 2 ulcers on the denervated compared with 37 on the innervated side.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of pyloroplasty, truncal vagotomy, and antrectomy on parietal cell regeneration in experimental gastric wounds in the rat. A light and electron microscopic study

Parietal cell regeneration in cauterized gastric wounds was studied in rats after antrectomy (Billroth I), pyloroplasty, and truncal vagotomy with pyloroplasty. Six to eight animals in each group were killed 90 or 130 days after operation, and in each rat stereological data were obtained from electron micrographs of 15 to 20 parietal cells from the wound area, from the normal mucosa beside the wounds, and from the mucosa in unoperated controls. Antrectomy reduced parietal cell size and mucosal thickness in normal mucosa and retarded parietal cell maturation and reduced mucosal thickness in the healing wounds. Pyloroplasty slightly reduced parietal cell size in normal mucosa and retarded maturation of the parietal cells in the wounds. If truncal vagotomy was added, the reduction in parietal cell size induced by the pyloroplasty was prevented in normal mucosa.

Quantitative ultrastructural studies on rat gastric zymogen cells under different physiological and experimental conditions

Quantitative electron microscopical measurements performed on gastric zymogen cells were aimed at determinations of size and volume density of the zymogen granules, and size of cell and nuclear profiles. 17 groups of rats each comprising 6-8 animals were investigated: five of these groups were used to study the influence of fasting and feeding, three groups were killed at different intervals after a pilocarpine injection, and four other groups were investigated after an atropine injection. The remaining five groups of rats were operated on: vagotomy was performed on one group, vagotomy + pyloroplasty on another, pyloroplasty on the third group, and antrectomy on the last two groups. The operated rats were sacrificed 4 or 10 weeks after the operations. Pilocarpine was more effective than feeding in reducing the size and the amount of zymogen granules. After atropine the size and amount of zymogen granules tended to increase. Ten weeks after pyloroplasty, vagotomy + pyloroplasty, or antrectomy the mean size of the zymogen cells was reduced. Loss of trophic vagal impulses, duodenal regurgitation, and abnormal serum gastrin levels are factors which might be responsible for the zymogen cell hypotrophy in operated rats.

Further studies on the mode of action of isoprenaline on gastric secretion in the conscious rat

1 The effect of isoprenaline on gastric secretion evoked by various means has been studied in conscious rats provided with Pavlov and Heidenhain pouches. 2 Interdigestive acid secretion in the Pavlov pouch was reduced by isoprenaline, whereas pepsin secretion was unaltered. 3 Central vagal stimulation effected by 2-deoxy-D-glucose injection evoked a gastric secretory response that was substantially reduced by isoprenaline. 4 2-Deoxy-D-glucose increased the mobilization of gastric mucosal histamine, an effect that was prevented by isoprenaline. 5 Isoprenaline infusion alone induced a slight increase in histamine mobilization and also a considerable elevation of immunoreactive serum gastrin concentration. 6 The secretory response to food in the Pavlov pouch was almost abolished by isoprenaline. 7 Although the acid response to histamine in the Heidenhain pouch was susceptible to isoprenaline inhibition, that to methacholine was not. 8 Pepsin secretion in the Heidenhain pouch preparation stimulated by histamine or methacholine seemed to be enhanced by isoprenaline.

The role of cholinergic excitation in the formation of histamine within the rat gastric mucosa

In the absence of the antrum, central vagal excitation and distension of the stomach accelerated the rate of formation of gastric mucosal histamine. The effect of vagus stimulation was abolished by truncal vagotomy or atropine whereas that of distension by atropine. After truncal vagotomy, distension was still effective in accelerating the formation of the amine. Furthermore, mucosal histamine formation in the fasting state was reduced by truncal vagotomy and atropine injection.