Tissue changes in the adult tryptophan-deficient rat.

In early studies histological methods were largely empirical and thus unequal to the demonstration of changes that must have existed in the tissues of animals on deficient diets. Thus, although Willcock & Hopkins (1906) did not observe any histopathological changes in the young tryptophan-deficient mice used in their classical experiments, moribund adult rats maintained on a tryptophan-deficient diet for more than IOO days (Cole & Robson, 195 I) were in such poor condition that it seemed possible that changes, detectable by the improved techniques now available, might have occurred in their tissues. Though some histological methods may be considered reliable within specified limits from a qualitative point of view, agreement with quantitative chemical estimations is not always satisfactory and it seemed useful to carry out such a comparison for proteins, fats and glycogen in the liver of deficient and control rats in a further experiment. The results of the preliminary and main investigations showed that the organs of adult rats most affected by prolonged tryptophan deficiency were, firstly, the liver, gonads and endocrine glands, i.e. organs having a secretory function and high metabolic turnover, and secondly, tissues with a high rate of replacement, particularly epithelia and blood. Albanese & Buschke (1942) and Albanese, Randall & Holt (1943) showed that in young rats continuously growing structures, such as epithelia and reproductive organs, bear the brunt of tryptophan deficiency. Severe signs were more rapidly manifest in their weanling rats than in the adult rats described here, which were used to avoid complications introduced by failure of growth.