ORIGINAL PAPER
The effect of repeated endotoxin injections on gonadotropin secretion in ewes
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The Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, 05-110 Jabłonna, Poland
Publication date: 2014-08-20
Corresponding author
A. P. Herman
The Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, 05-110 Jabłonna, Poland
J. Anim. Feed Sci. 2014;23(3):217-221
KEYWORDS
ABSTRACT
Although it is well known that acute inflammation induced by
a single injection of the bacterial endotoxin, lipopolysaccharide (LPS), induces
a stress response and suppresses luteinizing hormone (LH) secretion, the effects
of repeated endotoxin administration on gonadotropin secretion in sheep
have not been studied yet. In this work, the influence of inflammation induced
by six days of intravenous LPS injection (400 ng· kg–1 per day) on the release
of LH and follicle-stimulating (FSH) hormones was evaluated. Anoestrous ewes
were bled twice a day 1 h before and 3 h after LPS injection. Endotoxin injection
decreased (P < 0.05) the release of LH from the first day of the experiment.
Moreover, on day 5, the suppression of LH secretion was sustained and
could also be detected in the samples collected before the next LPS injection.
In contrast, elevation (P < 0.05) of FSH release was detected starting from
the second dose of the endotoxin. The increased FSH concentration persisted
until the end of the experiment. Each LPS injection stimulated (P < 0.05) cortisol
release, but from days 3 to 6, this elevation was about three times lower
than the level determined during the first two days. The obtained results show
that ewes exposed to repeated administration of endotoxin lost their ability to
restore proper LH release relatively quickly. This disturbance in gonadotropin
secretion could, in part, be associated with the stress induced by LPS, as well
as with endotoxin-induced inflammatory challenges.
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