The Effect of the Quality of Protein on the Estrous Cycle

Abstract

Rats maintained on a diet containing 5% of casein as the chief source of protein soon cease to exhibit the characteristic vaginal changes of estrus. The anestrous period is correlated with hypotypical ovaries and atrophic condition of the whole reproductive system. The failure of ovulation is indicated by atretic follicles and the absence of new corpora lutea. The addition of gelatin, rich in lysine, brings about only a partial response in the estrous cycle. When 5% of gliadin, poor in lysine, is added to the low casein diet ovulation occurs and the normal sexual rhythm is immediately resumed. It is evident that a deficiency of amino acids other than lysine causes an aberration of the estrous cycle, and it seems that when the dietary protein is inadequate for growth the sexual behavior is likewise adversely influenced. No permanent sterility results from feeding diets qualitatively or quantitatively deficient in protein if the necessary stimulus for ovulation is subsequently provided.