Ileo-caecal resection induced pancreatic growth in rats

Effects of raw soya diet and cholecystokinin receptor blockade on pancreatic growth and tumor initiation in the hamster

Raw soya diet in the hamster had short-term trophic effects on the pancreas, causing significant increases in pancreatic weight, DNA, RNA, and protein. These changes appear to be mediated by cholecystokinin (CCK) because the increases were blocked by infusion of the CCKA receptor antagonist, MK329. Raw soya diet significantly increased plasma levels of CCK in both the short-term and long-term studies. However, raw soya did not potentiate pancreatic cancer in hamsters treated with N-nitrosobis(2-oxopropyl)amine (BOP). Infusion of MK329 during the initiation period of carcinogenesis did not change tumor incidence or yield, suggesting that endogenous CCK does not influence tumor induction during the initiation period in the hamster.

Experimental pancreatic hyperplasia and neoplasia: effects of dietary and surgical manipulation

Several studies carried out during the past two decades have investigated the effect of dietary and surgical manipulation on pancreatic growth and carcinogenesis. Diets high in trypsin inhibitor stimulate pancreatic growth and increase the formation of preneoplastic lesions and carcinomas in the rat pancreas. Cholecystokinin (CCK) is the key intermediary in this response, since both natural and synthetic trypsin inhibitors increase circulating levels of the hormone and CCK antagonists largely prevent these changes. Fatty acids enhance pancreatic carcinogenesis in both rats and hamsters, whereas protein appears to have a protective role in the rat, but to increase tumour yields in the hamster. Several surgical operations affect the pancreas. Pancreatobiliary diversion and partial gastrectomy stimulate pancreatic growth and enhance carcinogenesis, probably by means of increased CCK release. Complete duodenogastric reflux has similar effects on the pancreas but the gut peptide involved is gastrin. Although massive small bowel resection increases pancreatic growth, the marked reduction in caloric absorption probably explains its failure to enhance carcinogenesis. CCK and enteroglucagon might work in concert to modulate the tropic response of the pancreas to small bowel resection. In the pancreas, as in the large intestine, hyperplasia appears to precede and predispose to neoplasia.

Biology of pancreatic cancer

Pancreatic cancer is the fifth leading cause of death from malignant disease in Western society. Apart from the fortunate few patients who present with a resectable small pancreatic adenocarcinoma, conventional treatment offers no hope of cure and has little palliative value. Over the past two decades major steps have been made in our understanding of the biology of pancreatic growth and neoplasia. This review sets out to explore these advances, firstly in the regulation of normal pancreatic growth, and secondly the mechanism which may be involved in malignant change of the exocrine pancreas. From an understanding of this new biology, new treatment strategies may be possible for patients with pancreatic cancer.

Meal-stimulated exocrine pancreatic secretion and release of GI peptides in normal and nicotine-treated rats

In rats, treated chronically with saline and nicotine, we studied the postprandial release of gastrin and cholecystokinin by specific radioimmunoassays and simultaneously measured secretory outputs of the exocrine pancreas. Rats were prepared surgically with gastric and pancreatic fistulas. Meal-stimulated release of peptides and exocrine secretory outputs were measured 24 h postoperatively in conscious rats. Infusion of food via intragastric cannula significantly stimulated plasma gastrin levels in both control and nicotine treated rats. Postprandial gastrin levels in nicotine treated rats were significantly higher compared to gastrin levels obtained after food in untreated control rats. Plasma CCK levels were increased in both groups after food. These levels remained significantly elevated from the basal values only for a transient period following infusion of the liquid meal. There were no differences in postprandial plasma CCK levels between the two groups. Outputs of exocrine pancreatic volume, protein and trypsin increased significantly after food in both control and nicotine treated groups of rats. The differences in outputs of volume and protein between the two groups of rats were not significant; however, the trypsin outputs in the nicotine rats were decreased significantly when compared to control rats. The data indicate that in rats, administration of food stimulated the release of immunoreactive gastrin and CCK with concomitant increase in exocrine pancreatic secretions of volume, protein and trypsin. Chronic nicotine treatment and its effect on food, however, appeared to have induced hyperfunction of G-cells that resulted in increased gastrin secretion and a decrease in trypsin secretion by exocrine pancreas. These data may have important implications in the etiology of the development of exocrine pancreatic dysfunction in chronic smokers.

Weight loss and altered circulating GI peptide levels of rats exposed chronically to nicotine

This study was undertaken in male Sprague-Dawley rats to test the hypothesis that chronic ingestion of a low dose of nicotine suppresses body weight gain. The results from this study suggest that chronic nicotine ingestion induces weight loss in rats without the loss of their food intake. To determine whether the nicotine-induced body weight reductions are associated with endocrinological changes, the levels of gastrin and CCK in plasma were measured by specific radioimmunoassays and were found significantly elevated during chronic ingestion of nicotine. The data indicate that reduction of body weight mass by nicotine might be dependent on both hormonal and metabolic factors.