Acute and subacute effects of naturally occurring estrogens on luteinizing hormone secretion in the ovariectomized rat: Part 1.
Acute pretreatment of ovariectomized rats with genistein (G) alters gonadotropin-releasing hormone-(GnRH)-induced LH secretion in a fashion comparable to estradiol (E2). In the present studies we wished to (A) determine whether G can acutely inhibit tonic LH secretion by oral (po) or intravenous (iv) routes, (B) compare GnRH-induced LH responses following higher iv dose pretreatments with G or E2, and (C) determine effects of G or E2 pretreatments on progesterone (P)-induced secretion of LH. Mature Charles River CD rats were ovariectomized, and 2 to 5 weeks later intraatrial cannulae were placed. Serial blood samples were drawn and LH was measured by RIA. In experiments 1 and 2, G or E2 was administered acutely by gavage or iv, while in experiment 3, G and E2 were given subcutaneously (sc) oil 3 days prior to cannulation and sampling. Acute po administration of vehicle or G (0.1, 1.0, and 10 mg/kg BW) had no effect on tonic LH, while E2 suppressed LH at all doses (0.1, 1.0, and 10 mg/kg BW). Acute iv administration of vehicle and higher doses of G (1 and 10 mg/kg BW) had no effect on tonic LH, while the lowest dose G (0.1 mg/kg BW) and all doses of E2 (0.1, 1, and 10 mg/kg BW) suppressed tonic LH. In the iv-treated rats, GnRH-induced LH secretion was more profoundly suppressed by G at all doses than by E2.(ABSTRACT TRUNCATED AT 250 WORDS)
Hughes
C L
CL
Department of Obstetrics and Gynecology, Duke University Medical Center, Durham, North Carolina 27710.
Kaldas
R S
RS
Weisinger
A S
AS
McCants
C E
CE
Basham
K B
KB
D000818:Animals; D004958:Estradiol / Q000494:pharmacology; D004968:Estrogens, Non-Steroidal / Q000494:pharmacology*; D005260:Female; D019833:Genistein; D007987:Gonadotropin-Releasing Hormone / Q000502:physiology; D007529:Isoflavones / Q000494:pharmacology*; D007986:Luteinizing Hormone / Q000378:metabolism*; D010052:Ovariectomy; D010053:Ovary / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D013997:Time Factors
D004968:Estrogens, Non-Steroidal; D007529:Isoflavones; D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D007986:Luteinizing Hormone; D019833:Genistein