title: Effect of dietary protein levels on sex hormones in growing male rats kept under constant darkness.
abstract: The purpose of this experiment was to clarify the effects of dietary protein levels on the gonadal development and sex hormones in male rats kept under constant darkness as a model of disturbed daily rhythm. Four-week-old male rats (Fischer 344 strain) were kept under constant darkness or normal lighting (12-h light/dark cycle). Two kinds of experimental diet were prepared, one with low dietary protein levels (9% casein) and one with normal levels (18% casein). Harper mineral mixture and Panvitan were used as mineral and vitamin sources, respectively. After 4 weeks, gonadal weight, serum testosterone, and other hormone contents were evaluated. The gonadal weight in the constant darkness groups (D-groups) was lower than that in the normal lighting groups (N-groups). Although the low-protein diet in the D-groups significantly reduced gonadal weight, the normal-protein diet mitigated the reduction of gonadal weight in rats kept under constant darkness. Serum testosterone and androstenedione concentrations were lower in D-group rats fed the low-protein diet. There were no effects of lighting condition or protein levels on serum luteinizing hormone (LH), follicle- stimulating hormone (FSH), or progesterone concentrations. These results indicate that the suppression of gonadal development in D-group rats fed the low-protein diet was caused by low testosterone, which we attribute to the inhibition of synthesized androstenedione, a precursor of testosterone. The present study showed that constant darkness and the low- protein diet inhibited the synthetic pathway from progesterone to androstenedione.
authors.affiliation: Department of Nutrition and Life Science, Kanagawa Institute of Technology, 1030 Shimo-Ogino, Atsugi, Kanagawa 243-0292, Japan.
authors.forename: Miho
authors.initials: M
authors.lastname: Hanai
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Esashi
mesh_terms: D000818:Animals; D021081:Chronobiology Disorders / Q000473:pathology* / Q000503:physiopathology*; D018753:Diet, Protein-Restricted / Q000009:adverse effects*; D004044:Dietary Proteins / Q000008:administration & dosage; D004797:Enzyme-Linked Immunosorbent Assay; D005837:Genitalia, Male / Q000187:drug effects / Q000254:growth & development; D012739:Gonadal Steroid Hormones / Q000097:blood; D006065:Gonadotropins, Pituitary / Q000097:blood; D008027:Light; D008297:Male; D009929:Organ Size / Q000187:drug effects; D011863:Radioimmunoassay; D051381:Rats / Q000254:growth & development / Q000502:physiology*; D011916:Rats, Inbred F344; D013739:Testosterone / Q000096:biosynthesis / Q000097:blood*; D014815:Vitamins / Q000008:administration & dosage*
chemical_list: D004044:Dietary Proteins; D012739:Gonadal Steroid Hormones; D006065:Gonadotropins, Pituitary; D014815:Vitamins; D013739:Testosterone