Hypertrophy and hyperplasia of the neonatal rat exocrine pancreas induced by orally administered soybean trypsin inhibitor

Measurement of RNA, DNA, protein and phospholipid synthesis in the neonatal rat pancreas following the oral administration of partially purified soybean trypsin inhibitor demonstrates an enhanced synthesis of all these constituents. Evidence of true hyperplasia in addition to this cellular hypertrophy is provided by an increased mitotic activity in the exocrine pancreas following a wave of enhanced [3H] thymidine incorporation into DNA. Complete inhibition of the stimulated RNA synthesis by low doses of actinomycin D indicates the importance of transcription as a regulatory step in the response of the exocrine pancreas to trophic stimulation by this means. Collateral observations of [3H] thymidine and [14C] orotic acid incorporation into liver DNA and RNA, respectively, fail to demonstrate comparable changes confirming the probable specificity of the trypsin inhibitor induced effect on the exocrine pancreas. It is suggested that the pronounced trophic effect of orally administered soybean trypsin inhibitor in the neonatal rat pancreas may serve as a useful model for the study of regulatory mechanisms of nucleic acid and protein synthesis in the mammalian pancreas.

Abolishment of oral trypsin inhibitor stimulation of the rat exocrine pancreas after duodeno-jejunal resection

The effect of long-term oral trypsin inhibitor administration on the exocrine pancreas was studied in unoperated rats and in rats operated on by a 30% proximal small intestinal resection. The following observations were made: in unoperated rats sacrificed 18 hours after the last trypsin inhibitor ingestion there was an increase of the wet weight of pancreas, increase of the pancreatic protein, and an increase of pancreatic and intestinal trypsin(ogen) and of pancreatic amylase by comparison with the controls. In operated rats, treated and examined in an identical way, no influences on the exocrine pancreas were found. It is suggested that the abolishment of the trypsin inhibitor effects on the exocrine pancreas in operated rats reflects the removal of the site of production of one or more intestinal hormone(s) or factor(s) responsible for these effects. In unoperated rats examined 4 hours after the last trypsin inhibitor ingestion a reduction of the pancreatic trypsinogen and amylase and an increase of the intestinal amylase were found, indicating a secretory response of the pancreas to the intraluminal trypsin inhibitor; the low values of intestinal trypsin found in these rats probably reflect inhibition of rat trypsin by the bovine lung trypsin inhibitor.

Oral trypsin-inhibitor-induced improvement of the exocrine and endocrine pancreatic functions in alloxan diabetic rats

Studies are presented dealing with the effect on the exocrine and endocrine pancreas of long-term oral trypsin inhibitor administration to alloxan diabetic rats. Three categories of rats were used: a) normal rats, b) alloxan diabetic rats, and c) alloxan diabetic rats treated with the trypsin inhibitor. 1. The concentration of amylase in both pancreas and intestinal contents were markedly decreased in alloxan diabetic rats as compared with normal rats, whereas the concentrations of lipase and trypsin(ogen) were practically unaffected by the diabetic state. 2. Trypsin inhibitor treatment of diabetic rats enhanced the concentrations of both amylase, trypsin(ogen), and lipase in pancreas and intestinal contents when compared with untreated diabetic controls. 3. Alloxan diabetic rats treated with trypsin inhibitor displayed an increased weight gain, increased pancreatic weight, and increased pancreatic protein concentration as compared with the untreated diabetic controls. 4. Alloxan diabetic rats treated for 3 or 5 weeks with the trypsin inhibitor were found to have decreased basal blood glucose levels and an increased plasma insulin: blood glucose ratio as compared to the untreated diabetic controls. 5. There was no apparent difference in the glucose elimination rate after I.V. glucose loads in diabetic rats given trypsin inhibitor and their diabetic controls. However, the insulin secretory response to the glucose stimulus was slightly improved in the trypsin inhibitor group. 6. Alloxan diabetic rats treated with trypsin inhibitor had an increased total pancreatic insulin content compared with their diabetic controls. It is concluded that long-term daily treatment with oral trypsin inhibitor in alloxan diabetic rats increased enzyme production and secretion in the exocrine pancreas, and produced an improvement of the diabetic condition of the animals. This improvement might partly be due to an increased pancreatic content and secretion of insulin.

Carbohydrate metabolism in normal and diabetic rats following long-term oral trypsin inhibitor administration

The effect of long-term oral trypsin inhibitor administration on blood glucose, plasma insulin, liver, and muscle glycogen and glucose utilization in vitro by peripheral tissues in normal and diabetic rats was studied. In normal rats the glycogen levels in liver and muscle were increased after 3 weeks of treatment. Glucose oxidation (14CO2-production) was augmented in muscle after 3 and 8 weeks and in liver after 3 weeks. An increased 14C-incorporation into glycogen from 14C-glucose and increased glycogen concentration after incubation were found in muscle after 3 weeks. In diabetic rats the basal blood glucose was decreased after 3 and 5 weeks of treatment, and the basal plasma insulin:blood glucose ratio increased after 5 weeks. The glycogen levels were increased after 3 and 5 weeks in liver. No effect on glucose oxidation (14CO2-production) in muscle was found. The 14C-incorporation into glycogen and the total glycogen content, however, was increased in muscle after both 3 and 5 weeks. Incubation of muscle tissue with serum from normal or diabetic rats treated with oral trypsin inhibitor for 3 and 5 weeks respectively had no apparent acute effects on the glucose metabolism. It is suggested that the observed action of oral trypsin inhibitors on glucose metabolism in peripheral tissues is mediated by one or more unknown gastrointestinal factor(s).

Studies on the reversibility of oral trypsin inhibitor induced changes of rat pancreatic exocrine enzyme activity and insulin secretory capacity

Rats were given a daily dose of bovine trypsin inhibitor for 3 weeks (Group 3 A) or 8 weeks (Group 8 A) via an orogastric tube. In another rat group the trypsin inhibitor after 3 weeks was replaced by water for another 5 weeks (Group 8 B). In group 3 A and 8 A an enlargement of the pancreatic gland was found. In group 3 A and 8A the pancreatic protein was increased. In group 3 A and 8 A the pancreatic trypsinogen increased in a more pronounced way than the amylase, while the pancreatic lipase was found to be uninfluenced by the trypsin inhibitor treatment. Five weeks after the cessation of a 3-week treatment the only remaining effect on the exocrine pancreas was an increase of the pancreatic trypsinogen. In group 3A an impairment of insulin secretion following intravenous L-isopropylnoradrenaline and glibenclamide was found. Glucose levels were similar to those of the control rats. Furthermore, a slight decrease of the pancreatic insulin content per g protein was found in these rats. In group 8A and 8B, the insulin secretory pattern was found to be normal following intravenous glucose administration, and an increased glucose elimination rate (k-value) compared with the control group suggested a favourable effect of oral trypsin inhibitor treatment on the glucose tolerance,

The effect of oral trypsin inhibitor on pancreatic damage in the rat

A study has been made of the influence of experimentally-induced pancreatic enlargement on pancreatic damage. Soybean trypsin inhibitor was fed to rats in doses sufficient to produce pancreatic enlargement. This agent was given both before and after the production of pancreatic necrosis by oral d,1-ethionine and before the induction of pancreatitis by ligation of the pancreatico-biliary duct. Generally there was no difference between the severity of pancreatic damage in rats fed trypsin inhibitor and in those on control diets. An exception was in rats given d,1-ethionine after treatment with soybean trypsin inhibitor. In these rats histology showed a less severe form of pancreatic necrosis.