Negative feedback inhibition of pancreatic exocrine secretion in humans

Pathological evaluation, clinical chemistry and plasma cholecystokinin in neonatal and young miniature swine fed soy trypsin inhibitor from 1 to 39 weeks of age

The potential toxicity of dietary soy trypsin inhibitor (TI) was evaluated in neonatal miniature swine. From 1 to 6 weeks of age, two groups of male piglets were artificially reared in an Autosow and automatically fed either TI or control liquid diet. From 6 to 39 weeks of age, these two groups were fed either TI or control chow diet. A third group, sow control (SC), suckled from birth to 6 weeks of age, were also weaned to control chow from 6 to 39 weeks of age. Clinical chemistry and plasma cholecystokinin (CCK) determined at 6, 18, 30 and 39 weeks of age, and serum amylase activity with gross and histopathological analyses of major organs at 6 and 39 weeks of age are reported. TI had no effect on plasma CCK, serum amylase activity, or numerous clinical chemistry values. TI-fed piglets had a larger relative liver weight at 6 weeks of age. Relative pancreas weight decreased with age but was not affected by TI. Gross and histopathological analyses of major organs, except the spleen, were within normal limits. Increased incidence of extramedullary hematopoiesis was noted in the spleen of the TI group at 6 but not at 39 weeks of age. There was no consistent pattern in immunohistochemical foci for secretin, gastrin releasing polypeptide or CCK, and no change in DNA, RNA, mitotic index or nuclear density of pancreatic cells. At 6 weeks of age, TI increased pancreatic protein and amylase activity but not trypsin or chymotrypsin activity. None of the effects suggested that this dose of TI was toxic to either the neonatal or sexually mature miniature male swine.

Pancreatic response in rats and mice to trypsin inhibitors from soy and potato after short- and long-term dietary exposure

The effects on the pancreas of chronic (95 wk) dietary exposure to protease inhibitors from soy and potato were compared in rats and mice. Soy and potato trypsin inhibitor (TI) concentrates were prepared from defatted raw soy flour and potato juice, respectively, by selective precipitation and ultrafiltration. Animals were fed a diet in which casein supplied approximately 20% protein. Each concentrate (less than 1% of the diet) was added to provide 100 and 200 mg of trypsin inhibitor activity per 100 g of diet. In short-term (28 d) experiments in rats, both sources of TI decreased the apparent nutritional quality of casein and produced pancreatic hypertrophy consistent with a hormonally mediated feedback mechanism for pancreatic adaptation to diet that is interactive with the nutritional status of the animal. After long-term feeding (95 wk), soy and potato TI produced dose-related pancreatic pathology in rats consisting of nodular hyperplasia and acinar adenoma, which was typical of that associated with raw soy flour. Although mice responded similarly to rats to soy TI in short-term (28-d) feeding experiments, they were resistant to the formation of these lesions following long-term feeding. This considerable species variation in propensity to develop preneoplastic and neoplastic lesions of the pancreas is not predicted by the short-term hypertrophic and hyperplastic response of the pancreas to TI.

Comparative subacute effects of dietary raw soya flour on the pancreas of three species, the marmoset, mouse and rat

Subacute changes induced in the pancreas by raw soya flour have been studied in three species. The raw soya flour was fed to male Sprague-Dawley rats and male CD-1 mice for 2, 4 or 8 days at a level of 50% (w/w) in the diet, and to male and female marmosets for 2 or 7 days at 20% (w/w) in the diet. The stathmokinetic method was used to study mitotic activity in the pancreas, and mean acinar cell area was calculated using an image analysis system. The relative weight of the pancreas in the rat and mouse increased during dosing, but that of the marmoset did not. No proliferative or trophic effects were observed in marmoset pancreas, but in both the mouse and rat a transient increase in mitotic activity was followed by a steady increase in acinar cell size.