Growth, digestibility and enzymatic activities in the pancreas and intestines of hamsters fed raw and heated soy flour

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.

Chemopreventive agents: protease inhibitors

Certain protease inhibitors, called the anticarcinogenic protease inhibitors in this review, are capable of preventing carcinogenesis in a wide variety of in vivo and in vitro model systems. The anticarcinogenic protease inhibitors are extremely potent agents with the ability to prevent cancer, with some unique characteristics as anticarcinogenic agents. The anticarcinogenic protease inhibitors have the ability to irreversibly suppress the carcinogenic process. They do not have to be continuously present to suppress carcinogenesis. They can be effective when applied in both in vivo and in vitro carcinogenesis assay systems at long time periods after carcinogen exposure, and are effective as anticarcinogenic agents at extremely low molar concentrations. While several different types of protease inhibitors can prevent the carcinogenic process, the most potent of the anticarcinogenic protease inhibitors on a molar basis are those with the ability to inhibit chymotrypsin or chymotrypsin-like proteases. The soybean-derived protease inhibitor, Bowman-Birk inhibitor (BBI), is a potent chymotrypsin inhibitor that has been extensively studied for its ability to prevent carcinogenesis in many different model systems. Much of this review is focused on the characteristics of BBI as the anticarcinogenic protease inhibitor, as this is the protease inhibitor that has risen to the human trial stage as a human cancer chemopreventive agent. Part of this review hypothesizes that the Bowman-Birk family of protease inhibitors plays a role in plants similar to that of alpha1-antichymotrypsin in people. Both BBI and alpha1-antichymotrypsin are potent inhibitors of chymotrypsin and chymotrypsin-like enzymes, are highly anti-inflammatory, and are thought to play important roles in the defense of their respective organisms. It is believed that BBI will be shown to play a major role in the prevention and/or treatment of several different diseases, in addition to cancer.

Effects of the synthetic trypsin inhibitor camostate on the development of N-nitrosobis(2-oxopropyl)amine-induced pancreatic lesions in hamsters

Trypsin inhibitors have been shown to promote pancreatic growth as well as the development of pancreatic tumours in rats. The present study was carried out to examine the effects of the synthetic trypsin inhibitor camostate on the growth of the pancreas and on the development of pancreatic preneoplastic and neoplastic lesions in hamsters treated with N-nitrosobis(2-oxopropyl)amine. A specific cholecystokinin-receptor antagonist was administered to determine the role of cholecystokinin in camostate action. The animals were killed 19 weeks after the first injection with N-nitrosobis(2-oxopropyl)amine. Camostate caused an increase in growth of the pancreas and a decrease in the number of (pre)neoplastic ductular pancreatic lesions. Lorglumide (CR-1409) did not influence these effects of camostate. It was concluded that rats and hamsters behave differently with regard to the effect of camostate on pancreatic growth and carcinogenesis.

Comparison of the effect of lorglumide on pancreatic growth stimulated by camostate in rat and hamster

We conducted a 14 day experiment in which we administered camostate (a trypsin inhibitor) and cholecystokinin alone or in combination with lorglumide, a cholecystokinin receptor antagonist, to both rats and hamsters. Plasma cholecystokinin levels were 21.7 +/- 3.2 pM and 19.6 +/- 2.5 pM with camostate, 16.3 +/- 2.4 pM and 14.8 +/- 2.2 pM with exogenous cholecystokinin, and 3.7 +/- 0.4 pM and 4.2 +/- 1.0 pM in control experiments in rats and hamsters, respectively. Both cholecystokinin and camostate were found to promote pancreatic growth in rats (18 +/- 4 and 111 +/- 7%, respectively) and hamsters (76 +/- 18 and 61 +/- 12%, respectively). Although lorglumide caused a decrease of this effect of camostate in both rats (78 +/- 5%) and hamsters (25 +/- 10%), it only became significant in rats. We therefore conclude that there are important interspecies differences in the role cholecystokinin plays in mediating the trophic effects of trypsin inhibitors on the pancreas.

Growth, digestibility, and enzyme activities in the pancreas and intestines of guinea-pigs fed on raw and heated soya-bean flour

The nutritional effects of giving raw (RSF) or heated (HSF) soya-bean flour to young guinea-pigs were investigated in trials 1 and 2, in which the levels of dietary protein were 120 and 190 g/kg diet respectively. The growth rate of animals fed on RSF was lower than that of those fed on HSF. Growth retardation of guinea-pigs fed on RSF was accompanied by a lower apparent digestibility of the protein (0.49-0.53) compared with HSF (0.67-0.76) and lower food conversion efficiency. In RSF-fed animals, increasing dietary protein affected growth and food conversion efficiency negatively. The pancreas of animals fed on RSF and HSF was similar in weight but secreted less trypsin, chymotrypsin and amylase, in RFS-fed animals. It was concluded that the mechanism by which raw soya-bean negatively affects the growth rate of guinea-pigs by reducing the activity of intestinal enzymes, differs from that suggested for rats and chicks, but is similar to that of pigs and calves.

Protease inhibitor and defective proteolysis in cystic fibrosis

Meconium specimens from 18 infants with cystic fibrosis (CF) had strong trypsin inhibitory activity (TIA). The same specimen, which contained increased quantities of undigested proteins, had normal concentrations of immunoreactive trypsin (IRT), but deficient trypsin catalytic activity (TCA). TIA was not detected in any specimen from non-CF infants who had high concentration of proteins comparable to that of CF infants. Subjecting meconium supernatant of CF infants to Sephadex G-75 gel filtration revealed that TCA was greatly enhanced in effluents after fractions were activated by porcine trypsin. TCA was present in the same fractions with IRT. The findings suggested that proteases were secreted into the intestinal lumen in CF infants prior to birth. Deficient proteolysis in the disease might be due to the presence of a trypsin inhibitor.

The failure of long-term feeding of raw soy flour, in the presence or absence of azaserine, to induce carcinogenic changes in the mouse pancreas

The effects of feeding mice raw or heated soy flours or casein in the presence and absence of injected azaserine were investigated over a period of 18 months. Although the feeding of raw soy flour (compared with heated soy flour or casein) caused a significant inhibition of growth and an enlargement of the pancreas, there was no macroscopic evidence of pancreatic nodules in any of the six experimental groups. Microscopic examination of the pancreas revealed a somewhat higher (not significant) incidence of atypical acinar cell nodules in all animals injected with azaserine, but this difference was little influenced by the diets themselves. We concluded that raw soy flour itself has no carcinogenic effect on the mouse pancreas and does not enhance the sensitivity of the mouse pancreas to azaserine. Thus, it cannot be assumed that the appearance of pancreatic nodules constitutes an obligatory sequela of pancreatic hypertrophy and/or hyperplasia in all species of animals.

Effect of long-term feeding of soy-based diets on the pancreas of Cebus monkeys

Feeding soy-based protein containing trypsin inhibitor causes pancreatic hypertrophy in the rat, and long-term feeding (up to 2 years) has revealed a high incidence of adenoma following hypertrophy. It was therefore of interest to determine whether the ingestion of soy-based protein has any adverse effects on the primate pancreas. A resource of 27 Cebus albifrons monkeys, previously used to evaluate the protein quality of several soy and milk proteins, has been maintained on semi-synthetic diets for 3 to 4 years; the protein sources for the diets were casein, lactalbumin, soy isolate and soy concentrate. In general the monkeys were in good physical health and their weights were appropriate for age and sex. Serum biochemical and hematological profiles were normal and there were no major differences between the groups. A pancreatic biopsy from both the head and tail region of the pancreas was taken from each monkey. Visual observation of the pancreas revealed no overt pathology; two independent histological examinations indicated no diet-related differences between groups, and biochemical analyses of trypsin, chymotrypsin, protein, DNA and RNA revealed no differences. It is concluded that feeding low level trypsin inhibitor-containing diets for up to 4 years caused no adverse effects in the pancreas of the Cebus nonhuman primate.

The effect of the long-term feeding of raw soy flour on the pancreas of the mouse and hamster

The effects of the long-term feeding of mice and hamsters with raw (RSF) or heated (HSF) soy flours were investigated both in the presence and absence of chemical carcinogens. Mice which had been fed RSF for 18 months had enlarged pancreas but only a relatively low incidence of atypical acinar cell nodules (AACN). Mice on either RSF or HSF were also relatively resistant to the carcinogenic effects of azaserine which is known to produce a high incidence of AACN in rats. Hamsters which had been fed RSF for 15 months did not exhibit pancreatic enlargement and had a very low incidence of pancreatic tumors. Although the incidence of tumors in hamsters which had been injected with N-nitrosobis (2-oxopropyl)amine and maintained on HSF was very high (88%), those on RSF had a tumor incidence of less than 10%. Thus, there appears to be a marked difference in the response of the pancreas in different species of animals to the long-term effects of feeding RSF. This should be taken into consideration in evaluating the potential carcinogenicity of the trypsin inhibitors.

Trophic effect of bombesin on the rat pancreas: is it mediated by the release of gastrin or cholecystokinin?

This work investigates the effect, on the rat pancreas, of a chronic administration of bombesin in function of the dose and duration of treatment and examines whether this effect may be mediated by the release of endogenous gastrin or cholecystokinin. Bombesin, administered three times daily for 5 or 15 days, induced a marked increase in pancreatic weight, its protein, RNA and enzyme contents with the dose of 10 micrograms/kg body weight; the ratios of pancreatic weight, protein and RNA contents to DNA contents increased significantly after a 5 day treatment, suggesting cellular hypertrophy. Pancreatic DNA content was markedly enhanced after a 15 day treatment, suggesting cellular hyperplasia. Antrectomy decreased plasma gastrin levels, but did not alter the pancreatico-trophic action of a 10 micrograms/kg bombesin treatment for 5 days. Proglumide, an inhibitor of cholecystokinin and gastrin in the pancreas, did not affect the growth of the pancreas induced by a 10 micrograms/kg bombesin treatment for 5 days. It is concluded that chronic bombesin induces, in the rat pancreas, cellular hypertrophy or hyperplasia depending on the duration of treatment. Pancreatic hypertrophy is not mediated by the release of endogenous gastrin or cholecystokinin.