Abstract
In two year feeding trials, histologic changes in the pancreas of the Wistar rat were evaluated after chronic dietary exposure to raw and heated, dehulled, defatted soy flour and soy protein isolates which provided a range of trypsin inhibitor (TI) concentrations from 93 to 1271 mg/100 g diet. Also investigated was the nutritional interaction of level of dietary protein with the development of pancreatic pathology. Graded levels of TI were achieved from mixtures of raw and heated soy flour or protein isolate. Dietary protein levels were 10%, 20%, and 30%; the two higher levels obtained in some diets through casein supplementation. A total of 26 diets, including casein controls, were fed to groups of 40 male rats. Growth rates with these diets were commensurate with protein quality and level. Mortality rates tended to be slightly greater in the higher protein diets, and rats fed only raw soy as a source of protein survived well.
Two lesions, nodular hyperplasia (NH) and acinar adenoma (AA) constituted the major pathological findings in the pancreas, and the incidence rates of both were positively associated with the concentration of dietary TI. The incidences of pancreatic NH and AA compared to those of the corresponding casein control were significantly elevated in rats fed heated soy flour supplying 10% protein and the lowest level of TI investigated (93 mg/100 g diet). At low levels of TI (≦215 mg/100 g diet), supplementation by casein to raise the concentration of protein from 10% to 20% and 30% reduced the frequency of NH and AA. When the dose-response data for NH and AA was linearized by plotting the probit of percent incidence against log of TI concentration per gram of dietary protein, the response to soy flour and soy protein isolate was not significantly different. Numerous lesions commonly found in the aging rat were diagnosed, and modulation of their rate of occurrence by nutritional factors associated with the diets was apparent in some instances.
Similar content being viewed by others
References
Altman NH, Goodman DG (1979) Neoplastic Diseases. In: Baker HJ, Lindsey JR, Weisbroth SH (eds) The Laboratory Rat, Vol I Biology and Diseases. New York: Academic Press, pp 333–376
Anver MR, Cohen BJ (1979) Lesions associated with aging. In: Baker HJ, Lindsey JR, Weisbroth SH (eds) The Laboratory Rat, Vol I Biology and Diseases. New York: Academic Press, pp 377–399
Bliss CI (1967) Analysis of fourfold tables. In: Statistics in Biology Vol I. New York: McGraw-Hill Book Company, pp 53–91
Booth AN, Robbins DJ, Ribelin WE, DeEds F, Smith AK, Rackis JJ (1964) Prolonged pancreatic hypertrophy and reversibility in rats fed raw soybean meal. Proc Soc Exp Biol Med 116:1067–1069
Cox DR (1972) Regression models and life tables. JR Stat Soc B. 34:187–220
Crass RA, Morgan RGH (1981) Rapid changes in pancreatic DNA, RNA and protein in the rat during pancreatic enlargement and involution. Int J Vitam Res 51:85–91
Duncan DB (1955) Multiple range and multiple F tests. Biometrics 11:1–42
Gart JJ, Chu KC, Tarone RE (1979) Statistical issues in interpretation of chronic bioassay tests for carcinogenicity. J Natl Cancer Inst 62:957–974
Gaunt IF, Hardy J, Grasso P, Gangolli SD, Butterworth KR (1976) Long-term toxicity of cyclohexylamine hydrochloride in the rat. Food Cosmet Toxicol 14:255–267
Goodman DG, Ward JM, Squire RA, Chu KC, Linhart MS (1979) Neoplastic and nonneoplastic lesions in aging F344 rats. Toxicol Appl Pharmacol 48:237–248
Gray JE (1977) Chronic progressive nephrosis in the albino rat. Crit Rev in Toxicol 5:115–144
Grizzle JE, Starmer CF, Koch GG (1969) Analysis of categorical data by linear models. Biometrics 25:489–504
Haseman JK (1983) Patterns of tumor incidence in two-year cancer bioassay feeding studies in Fischer 344 rats. Fundam Appl Toxicol 3:1–9
Kociba RJ, Keyes DG, Beyer JE, Carreon RM, Wade CE, Dittenber DA, Kalnins RP, Frauson LE, Park CN, Barnard SD, Hummel RA, Humiston CG (1978) Results of a two-year chronic toxicity and oncogenicity study of 2,3,7,8-tetrachlorodibenzo-p-dioxin in rats. Toxicol Appl Pharmacol 46:279–303
Kociba RJ, Keyes DG, Lisowe RW, Kalnins RP, Dittenber DD, Wade CE, Gorzinski SJ, Mahle NH, Schwetz BA (1979) Results of a two-year chronic toxicity and oncogenic study of rats ingesting diets containing 2,4,5-trichlorophenoxyacetic acid (2,4,S-T). Food Cosmet Toxicol 17:205–221
Liener IE, Nitsan Z, Srisangnam C, Rackis JJ, Gumbmann MR (1985) The USDA trypsin inhibitor study. II. Time-related biochemical changes in the pancreas. Qual Plant Foods Hum Nutr 35:243–257
Longnecker DS (1981) Pancreatic carcinoma in azaserine-treated rats: induction, classification and dietary modulation of incidence. Cancer 47:1562–1572
Longnecker DS (1983) Carcinogenesis in the pancreas. Arch Pathol Lab Med 107:54–58
McGuiness EE, Morgan RGH, Levison DA, Frape DL, Hopwood G, Wormsley KG (1980) The effects of long-term feeding of soya flour on the rat pancreas. Scand J Gastroenterol 15:497–502
Milman HA, Ward JM, Chu KC (1978) Pancreatic carcinogenesis and naturally occurring pancreatic neoplasms of rats and mice in the NCI carcinogenesis testing program. J Environ Pathol Toxicol 1:829–840
Peto R (1974) Guidelines on the analysis of tumour rates and death rates in experimental animals. Br J Cancer 29:101–105
Rackis JJ, Gumbmann MR, Liener IE (1985) The USDA trypsin inhibitor study. I. Background, objectives, and procedural details. Qual Plant Plant Foods Hum Nutr 35:213–242
Rowlatt U, Roe FJC (1967) Epithelial tumors of the rat pancreas. J Natl Cancer Inst 39:18–22
SAS Institute Inc (1980) The PHGLM procedure. In: Reinhardt PS (ed) SAS Supplemental Library User's Guide, 1980 Edition. Gary, NC: SAS Institute Inc, pp 119–131
SAS Institute Inc (1982) The GLM procedure. In: Ray AA (ed) SAS User's Guide: Statistics, 1982 Edition. Gary, NC: SAS Institute Inc, pp 139–199
Ibid. The FUNCAT procedure. pp 257–285
Ibid. The PROBIT procedure. pp 287–292
Sher SP (1982) Tumors in control hamsters, rats, and mice: literature tabulation. Crit Rev Toxicol 10:49–79
Spangler WL, Gumbmann MR, Liener IE, Rackis JJ (1985) The USDA trypsin inhibitor study. III. Sequential development of pancreatic pathology in rats. Qual Plant Plant Foods Hum Nutr 35:259–274
Author information
Authors and Affiliations
Additional information
Reference to a company and/or product named by the Department is only for purposes of information and does not imply approval or recommendation of the product to the exclusion of others which may also be suitable.
Rights and permissions
About this article
Cite this article
Gumbmann, M.R., Spangler, W.L., Dugan, G.M. et al. The USDA trypsin inhibitor study. IV. The chronic effects of soy flour and soy protein isolate on the pancreas in rats after two years. Plant Food Hum Nutr 35, 275–314 (1985). https://doi.org/10.1007/BF01092199
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF01092199