title: The estrous cycle and pituitary-ovarian function in Lewis and Fischer rats.
abstract: We have characterized the estrous cycle by obtaining vaginal smears, and quantitating estradiol (E), progesterone (P), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) plasma levels at different phases of the estrous cycle in Lewis (LEW/N) and Fischer (F344/N) rats. Comparison of the duration of the component phases of estrous showed LEW/N metestrous to be significantly longer than in F344/N rats while diestrous and estrous were significantly shorter; proestrous was identical. E levels in LEW/N rats were significantly greater than in F344/N rats only in the estrous phase of the cycle. P levels were significantly greater in LEW/N rats in all phases. LH and FSH levels in the two strains did not differ. Elevated E and P levels would be expected to be associated with increased corticosterone through inhibition of the glucocorticoid negative-feedback pathway. The data reported suggest that other modulating factors in corticotropin-releasing-factor synthesis/release could be overriding both the E and P effects upon hypothalamic-pituitary-adrenal axis responsiveness.
mesh_terms: D000818:Animals; D003345:Corticosterone / Q000097:blood; D004958:Estradiol / Q000097:blood; D004971:Estrus / Q000502:physiology*; D005246:Feedback; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology; D007986:Luteinizing Hormone / Q000097:blood; D010053:Ovary / Q000502:physiology*; D010903:Pituitary Gland, Anterior / Q000502:physiology*; D011374:Progesterone / Q000097:blood; D051381:Rats; D011916:Rats, Inbred F344 / Q000502:physiology*; D011917:Rats, Inbred Lew / Q000502:physiology*; D013997:Time Factors
chemical_list: D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D003345:Corticosterone