Amylase Secretion by Rat Pancreas Following Prolonged Stimulation by Unheated Soybean Flour

Abstract

Rats were fed diets containing either heated or unheated soybean flour for 3 months. Relative to body weight the pancreatic glands of rats fed the unheated soybean flour diet secreted the same volume but less protein and amylase, both in basal fasted state and following stimulation with pancreozymin. Administration of a test meal of unheated soybean flour, presumably stimulating secretion of pancreozymin, caused a smaller percentage reduction of amylase content in pancreases of rats chronically fed unheated soybean flour than in those subsisting on heated soybean flour diet. Pieces of pancreas derived from both groups of rats were incubated in the presence of two doses of pancreozymin. Pancreatic glands of both groups secreted similar amounts of amylase when stimulated by a low dose of pancreozymin. Pancreases of rats fed heated soybean flour, but not those of rats subsisting on unheated soybean flour, responded to a larger dose of pancreozymin with increased release of amylase. The results are interpreted as a manifestation of an increased activity of pancreozymin inactivating enzyme in body fluids of rats fed unheated soybean flour. However, fatigue of the pancreatic exocrine secretion apparatus resulting from prolonged stimulation by the heat-labile soybean trypsin inhibitors cannot be excluded.

The effect of fasting on enzyme levels in the enlarged and involuting rat pancreas

“…They found in this later study that the pancreas of fasted rats fed on RSF contained less amylase than the pancreas of fed RSF-fed rats and fasted HSF-fed rats, again in contrast to the present study. The reason for the differences between the studies reported by Konijn's group (Konijn et al 1970(Konijn et al , 1972 and the present study is not known. Factors which might contribute include the use by Konijn et ai.…”

“…This is in marked contrast to the present study in which the pancreas from fasted rats previously fed on RSF contained over four times as much amylase as the pancreas from fasted rats fed on HSF (5727 (SEM 602) U v. 1335 (SEM 154) U). In a later extension of their study, Konijn et al (1972) examined the effect of fasting and feeding on the enzyme content of rats fed on either RSF or HSF for 3 months. They found in this later study that the pancreas of fasted rats fed on RSF contained less amylase than the pancreas of fed RSF-fed rats and fasted HSF-fed rats, again in contrast to the present study.…”

Biological and physiological factors in soybeans

“…Konijn, et al, (150) reviewed the older literature on goitrogenicity of soybeans. As shown in Table VIII lack of iodine is the principle cause of goiter, but heat treatment abolished most of the goitrogenic activity (151).…”

Chronic and Acute Studies Indicating Absence of Exocrine Pancreatic Feedback Inhibition in Dogs

“…It was not possible to monitor the levels of protease zymogens within the pancreas during administration of the SBTI diets, and so it is uncer tain whether the decreased enzyme output observed while the dogs were fed the raw soybean diet was caused by a reduction in the amount of zymogen present in and synthesized by the acinar cells, or represents an impaired response to the hormonal stimulation. Such an impaired response to CCK has been reported in vitro for the secretion of amylase by the pancreas from rats fed unheated as opposed to heated soybean flour (28).…”