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Journal of Nutrition Vol. 100 No. 1 January 1970, pp. 94-100
Copyright © 1970 by American Society for Nutrition
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A Comparison of Tryptophan Pyrrolase Adaptation in Cattle, Sheep, and Rats1,2,

J. R. Carlson and I. A. Dyer

Department of Animal Sciences, Washington State University, Pullman, Washington 99163

Rats and cattle were given oral or intraperitoneal doses of DL-tryptophan, and the plasma tryptophan concentration and liver tryptophan pyrrolase activity were measured. In rats the plasma tryptophan concentration increased to a maximum in 1 to 2 hours followed by peak tryptophan pyrrolase activity at 4 to 6 hours. Doses of DL-tryptophan which were sufficient to elevate the plasma concentration of cattle to a level comparable to that in orally dosed rats did not result in increased liver tryptophan pyrrolase activity. Graded doses of prednisolone given alone or in combination with DL-tryptophan were more effective in increasing liver tryptophan pyrrolase activity in rats than similar doses of cortisol. Large doses of prednisolone and tryptophan were ineffective in increasing liver tryptophan pyrrolase activity in adult cattle and milk-fed calves. A small increase in enzyme activity was observed in similarly treated sheep. The results indicate that liver tryptophan pyrrolase activity is lower in ruminants than in control rats, and that large doses of prednisolone and tryptophan do not cause appreciable enzyme induction in these species within the same time period that is effective in rats.

1 Supported in part by Public Health Service Research Grant no. AI08285 from the National Institute of Allergy and Infectious Diseases, and in part by funds provided for biological and medical research by the State of Washington Initiative no. 171. Scientific paper no. 3321, College of Agriculture, Washington State University, Projects 1899, 1893, 3893.

2 Presented in part at American Institute of Nutrition meetings, Federation of American Societies for Experimental Biology, Atlantic City, N. J., April 1969.

Manuscript received 11 August 1969.




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