title: Inhibin-like activity in ovarian homogenates of prepubertal female rats and its physiological significance.
abstract: The presence and physiological significance of ovarian inhibin-like activity (ILA) in immature rats was studied by measuring ILA in ovarian homogenates and by studying the short-term changes in serum concentrations of FSH and LH after unilateral or bilateral ovariectomy. Inhibin-like activity in ovarian homogenates was estimated using an in-vitro bioassay system with dispersed rat anterior pituitary cells and subsequent measurement of FSH and LH levels in the spent pituitary cell medium. Inhibin-like activity, expressed in units/ovary, was undetectable in 13-day-old ovaries, was present in 18-day-old ovaries (5.8 units/ovary) and rose significantly to a value of 29.1 units/ovary on day 23. Another significant rise was seen between 28 and 33 days of age, with ILA reaching a value of 66.4 units/ovary, a value still well below that found in adult dioestrous ovaries (155.6 units/ovary). In the bioassay no systematic dose-dependent influence on LH secretion was found. Serum concentrations of FSH after unilateral or bilateral ovariectomy at 18 days of age showed no change at 5h and a significant (P less than 0.05) increase compared with sham-operated controls at 24 h after operation. At 23, 28 and 33 days of age significant increases in FSH concentration were seen at 5 and 8 h after both unilateral and bilateral ovariectomy. At 24 h after unilateral ovariectomy, FSH had returned to the control values in these rats, whereas after bilateral ovariectomy a further increase in FSH was seen.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D001681:Biological Assay; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D007265:Inhibins / Q000032:analysis / Q000502:physiology*; D007986:Luteinizing Hormone / Q000097:blood; D010052:Ovariectomy; D010053:Ovary / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012741:Sexual Maturation; D013997:Time Factors
chemical_list: D007265:Inhibins; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone