INFLUENCE OF DIFFERENT DIETARY PROTEIN LEVELS IN STARVATION ON THE ENDOCRINE SYSTEM OF MALE AND FEMALE RATS*

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Abstract
For 16 days, female and male rats, were given diets containing 25% of the calories consumed by normal controls. One starvation diet was the same as that given to the control animals; this "low-protein" starvation group therefore recived 25% of the quantity of protein given to the controls. The 2d, "high-protein" starvation group received a diet isocaloric with that of the low-protein group, but containing 4 times as much protein. Their protein intake was therefore identical with that of the controls. Body wt. loss was identical in the 2-starvation groups. The wt. loss of the pituitaries was more marked in the females than in the males. In the latter it was proportional to the loss of body wt., whereas it exceeded the body wt. loss in the females. The different levels of dietary protein did not influence the degree of pituitary wt. loss. The thyroid wts. in the males decreased in proportion to the loss of body wt.; in the females the relative wt. loss of the thyroid ex-ceeded that of the body. Thyroid function, as detd. by uptake of I131/mg. of thyroid tissue was decreased. Neither the wt. loss nor the decreased function of the thyroid was influenced by the level of dietary protein. The wt. of the adrenal glands of all starved animals was identical with that of the controls, indicating that the adrenals did not participate in the general wt. loss. Thus, there was "relative hypertrophy," such as is observed in acute, complete starvation, and not the atrophy of chronic inanition. The wt. of the testes and ovaries decreased in starvation. The wt. loss was less severe in animals on the protein intake, but the differences in gonadal wt. in the 2 starvation groups were not significant. The wt. loss of the seminal vesicles and of the uterus, chosen as representative target organs of androgens and estrogens, resp., was greater in the low-protein than in the high-protein starvation group. The response of the seminal vesicles of starved castrate males to exogenous testosterone was not influenced by the dietary protein level. This suggests that the testes of rats receiving the high-protein starvation diet secrete more testosterone than do those on the low-protein starvation diet. The wt. loss of the kidneys was greater in the low- than in the high-protein starvation group.