EurekaMag.com logo
+ Site Statistics
References:
52,725,316
Abstracts:
28,411,598
+ Search Articles
+ Subscribe to Site Feeds
EurekaMag Most Shared ContentMost Shared
EurekaMag PDF Full Text ContentPDF Full Text
+ PDF Full Text
Request PDF Full TextRequest PDF Full Text
+ Follow Us
Follow on FacebookFollow on Facebook
Follow on TwitterFollow on Twitter
Follow on Google+Follow on Google+
Follow on LinkedInFollow on LinkedIn

+ Translate

Suppression of preovulatory luteinizing hormone surges in heifers after intrauterine infusions of Escherichia coli endotoxin






American Journal of Veterinary Research 50(3): 368-373

Suppression of preovulatory luteinizing hormone surges in heifers after intrauterine infusions of Escherichia coli endotoxin

A study was conducted to test the hypothesis that high cortisol concentrations associated with products of infections (endotoxin) cause derangement in the neuroendocrine mechanism controlling ovulation in heifers. Eight Holstein heifers were given 2 injections of prostaglandin (PG), 11 days apart, to synchronize estrus. Starting from 25 hours after the second injection of PG (PG-2), the uterus of each heifer was infused with 5 ml of pyrogen-free water (control, n = 3) or Escherichia coli endotoxin (5 .mu.g/kg of body weight) in 5 ml of pyrogen-free water (treated, n = 5), once every 6 hours for 10 treatments. Blood samples were obtained every 15 minutes via indwelling jugular catheter for an hour before and 2 hours after each infusion, then hourly until an hour before the next infusion. Ultrasonography of the ovaries was performed every 12 hours, starting 24 hours after PG-2 injection until 96 hours after PG-2 injection. Serum concentrations of luteinizing hormone and cortisol were determined by validated radioimmunoassays. Changes in cortisol concentrations were not detected in control heifers with preovulatory luteinizing hormone surges at 60 to 66 hours after PG-2 injection, followed by ovulations 72 to 96 hours after PG-2 was injected. None of the treated heifers ovulated, and the resulting follicular cysts (14 to 18 mm diameter) persisted for 7 to 21 days. In all treated heifers, serum cortisol concentrations increased (4- to 10-fold) during the first 2 hours after each infusion and then decreased gradually until the next infusion. Luteinizing hormone concentrations remained at baseline values throughout the treatment period in all treated heifers. These findings suggested that endotoxin-induced increases in cortisol concentrations during the preovulatory period of the estrous cycle prevented ovulations by blunting the preovulatory luteinizing hormone surges.


Accession: 007847101

PMID: 2648904



Related references

Suppression of preovulatory lh surge in heifers following intrauterine infusions of lipopolysaccharide escherichia coli endotoxin during the preovulatory period. Biology of Reproduction 36(SUPPL 1): 94, 1987

Site of action for endotoxin-induced cortisol release in the suppression of preovulatory luteinizing hormone surges. Theriogenology 33(3): 637-643, 1990

Estradiol induces and progesterone inhibits the preovulatory surges of luteinizing hormone and follicle-stimulating hormone in heifers. Biology of Reproduction 26(4): 571-578, 1982

Changes in luteinizing hormone-releasing hormone content of discrete hypothalamic areas associated with spontaneous and induced preovulatory luteinizing hormone surges in the domestic hen. Biology of Reproduction 32(4): 813-819, 1985

Effect of naloxone and pulsatile luteinizing-hormone-releasing hormone infusions on oestradiol-induced luteinizing hormone surges in immature gilts. Journal of Reproduction and Fertility 97(2): 395-401, 1993

Control of the preovulatory luteinizing hormone and follicle stimulating hormone surges in cattle. Dissertation Abstracts International, B 42(6): 2148, 1981

Morphine inhibition of the preovulatory surges of plasma luteinizing hormone and follicle stimulating hormone in the rat. Endocrinology 101(6): 1726-1732, 1977

Neuropeptide Y potentiates luteinizing hormone (LH)-releasing hormone-induced LH secretion only under conditions leading to preovulatory LH surges. Endocrinology 131(6): 2946-2952, 1992

On differences between the preovulatory luteinizing hormone surges of 4- and 5-day cyclic rats. Journal of Endocrinology 70(3): 373-378, 1976

Serum luteinizing hormone concentrations in dairy heifers after intravenous and intrauterine administration of luteinizing hormone-releasing hormone. Veterinary Medicine, Small Animal Clinician 71(4): 419-422, 1976