Influence of dietary protein depletion and repletion on sex organ weight of male rats in relation to age

Studies were made on the effect of protein-free diet (PFD) feeding and on recovery from PFD feeding on sex organ weight, serum testosterone, pituitary prolactin and pituitary growth hormone content of young (4 months old) and old (18 months old) male rats. After 20 days of protein depletion, the testis weight remained almost the same, but the ratio of testis weight to body weight was higher in the lower age group, demonstrating a greater resistibility to protein deficiency in young rats. The weight of the seminal vesicle and prostate decreased on ingestion of PFD in both age groups, but a more marked increase was shown in refed young rats. Feeding of PFD for 20 days significantly reduced pituitary prolactin, pituitary growth hormone and serum testosterone in both age groups. Refeeding of protein increased these hormones, but a more marked increase was also observed in the younger group. These results seem to support the hypothesis that one of the important characteristics of an aging organism is its reduced capacity to adapt to environmental changes.