Applied reproductive endocrinology in SA Flashcards
What does inhibin do?
inhibits FSH not LH
How can the oestrous cycle be classified? 2
Ovarian secretions - Follicular/luteal
Vaginal cytology - pro-oestrous (E2), oestrous (E2), metoestrous (transitional), dioestrous (P4)
How are the bitch and queen’s cycles classified?
BITCH: mono-oestrous, non-seasonal, polytocous, spontaneuous ovulator
QUEEN: seasonally polyoestrous, polytocous, induced ovulator (in N. hemisphere, only non-cycling for one month)
How long is the follicular phase in bitches?
variable, 4-28 days
How long is the luteal phase in bitches?
60 days
How long are the phases in bitch cycles? Proestrous Estrous Pregnancy/diestrous Anoestrous
Proestrous - 9 days
Oestrous - 9 days (unusually long for domestics)
Pregnancy/dioestrous - 60 days (CL lasts this time if pregnant or not- problem PDing)
Anoestrous - >90 days (unknown why this happens at all)
Outline bitch LH levels:
Mid/late anoestrous
1 week before proestrous
Proestrous
Late proestrous
Mid/late anoestrous: low LH levels/pulsatility, <1ng/ml, occasional LH pulses (2-25 ng/ml) 4-24 hours apart
1 week before proestrous: frequency increases, pulses every 60-90 mins, levels increase to about 3 ng/ml
Proestrous: LH levels become lower and pulses less detectable
Late proestrous: LH reach peak levels, 8-15 ng/ml
Outline bitch FSH levels:
Mid/late anoestrous
1 week before proestrous
Proestrous
Late proestrous
Mid/late anoestrous: FSH levels high (near preovulatory), levels increase throughout
1 week before proestrous: modest increase (less pronounced than FSH)
Proestrous: FSH low
Late proestrous: peak occurs about 1 day after LH surge, modest increase in mean level
Outline bitch oestrogen levels:
Mid/late anoestrous
1 week before proestrous
Proestrous
Late proestrous
Mid/late anoestrous: remains low
1 week before proestrous: remain low
Proestrous: levels increase throughout from 10pg/ml to 120 pg/ml
Late proestrous: some secretion of oestradiol
True/False: measurement of P4 may be a good measure of impending ovulation.
True
Outline bitch progesterone levels:
Mid/late anoestrous 1 week before proestrous Proestrous Late proestrous Dioestrous
Mid/late anoestrous: low levels (<0.5ng/ml)
1 week before proestrous: low levels remain
Proestrous: levels increase slowly (0.2 to 0.8 ng/ml)
Late proestrous: 2-4ng/ml at time of LH surge, 4-10ng/ml at time of ovulation
Dioestrous: peak values of 15-90 ng/ml are reached POST-ovulation
What acts on the granulosa cell? What does it produce?
FSH and act on it
Produces progesterone and oestradiol (both to blood)
What acts on the theca cell? What does it produce?
LH acts on it Produces oestradiol (to blood)
When is oestrous sex behaviour shown? (BITCHES)
immediately after peak in oestradiol (suggested to be initiated by decrease in E:P ratio)
When does ovulation occur in relation to LH surge? (BITCHES)
2 days after.
Oocytes that are ovulated are immature (i.e. not completed 1st meiotic division). The rising levels of P4 (during luteinisation) could be the signal for completion of first meiotic division.
What happens to P4 in the luteal phase/dioestrous? (BITCHES)
P4 increases and plateaus during dioestrous and declines rapidly at luteolysis. This profile occurs in BOTH non-pregnant and pregnant animals
What is the source of P4 in bitches?
CL only (NOT placenta)
How are GnRH and luteolysis linked?
GnRH agonist (continuous) –> luteolysis
GnRH antagonist –> luteolysis
What does P4 do in luteal phase/dioestrous? (BITCHES)
regulates CL’s ability to secrete P4 (unusual!).
P4 antagonist (mifeprestone) causes luteolysis
inhibits luteal PGF2a secretion
inhibits PGF-R
What does PRL do in luteal phase/dioestrous? (BITCHES)
regulates P4 secretion from about day 25 after LH surge
PRL becomes the essential luteotrophin from day 25 after LH surge
It is important to note the PRL levels increase in both pregnant (5 times baseline) and non-pregnant (2-3 times baseline) animals
T/F: in bitches, there is no known luteolysin
True
T/F: in bitches, the PRL/LH -Rs can be expressed throughout luteal phase/dioestrous.
True
How can luteolysis be endogenously induced in bitches? 5
- PGF2a - high doses
- P4-R antagonist
- GnRH anatagonist
- GnRH agonist (continuously)
- PRL lowering doses of DA agonist
What causes luteolysis in pregnant bitches?
rapid pre-partum luteolysis due to feto-placental PGF2a release - essential for onset of parturition
What are the clinical signs of pseudopregnancy and what are they associated with?
CLINICAL SIGNS: extensive mammary gland development, lactation, behavioural changes typical of pregnancy and lactation
Seem to be associated with an increase in PRL levels
What sort of hormone is relaxin?
peptide, 2- chain structure, similar to insulin, family of 7 members
When are circulating concentrations of relaxin elevated?
about 21-24 days after LH surge
When is relaxin detectable in bitches?
non-detectable in non-pregnant animal - its sole source is the placentra, reaches about 5ng/ml in late pregnancy (days 40-50 gestation). It is the only pregnancy-specific protein identified in the dog. A relaxin enzyme immunoassay is available and has been used for PDing. Levels fall after parturition but remain detectable for at least 30 days during lactation. The increase in relaxin is coincident with the rise in PRL
How can oestrous be controlled in bitches?
OVH
Hormones - P4 (theoretically possible, not possible because not active orally and short duration of action when given PN). Synthetic progestagens (first generation = MAP, problem of potentially inducing GH secretion –> increased risk of acromegaly, mammary tumours and DM), PROLIGESTONE (PRG) - synthetic progestagen, specifically designed for prevention of oestrous in bitches/queens, strongly anti-gonadotrophic, weakly progestagenic, anti-oestrogenic so effectively controls vulval swelling and bleeding.
Testosterone - active orally BUT affects subsequent fertility and causes protrusion of clitoris and enlargement of vulva.
What are the signs of pseudoprenancy?
weight gain
mammary development
occasional lactation
from about day 45 after end of oestrous
behavioural signs sometimes - nest making, nursing inaminate objects, occasional false parturition
= clinical/overt pseudopregnancy
Luteal phase duration and concentrations of P4 are normal
Clinical signs associated with rise in plasma PRL and generally noted about 6 weeks after end of oestrous
Treatment - pseudopregnancy? 3
synthetic progestages - suppress PRL release
Oestrogens and androgens in combination - probably act like progestagens to suppress PRL
DA agonists (bromocriptine) inhibit PRL release (can induce vomiting)
True/false, in the queen, there is no proestrous phase and oestral behaviour occurs with few changes of external genitalia
True
What happens to the LH levels of the queen at copulation?
copulation leads to a rapid release of LH from the pituitary - usually multiple copulations are required to produce sufficient LH to induce ovulation
When do P4 levels change in the queen?
stay at baseline levels until after mating-induced LH surge. levels increase with ovulation and peak after 30 days. if not pregnant, P4 levels then decrease. In pregnant animals, P4 levels are maintained at an elevated level for a further 25-28 days. Queens that have ovulated but aren’t pregnant (pseudopregnant) do NOT return to oestrous until AFTER the levels of P4 have fallen to the baseline
Outline PRL in the queen
Elevated for the last 20 days of pregnancy and throughout lactation.
No changes in PRL levels during pseudopregnancy.
Theory: PRL drives CL to survive.
What is the interoestrous interval in Queens?
may be a useful guide as to whethe rovulation or conception has failed to occur.
unmated queens or mated queens that fail to ovulate have an interoesetrous interval of approximately 21 days (no luteal phase)
mated queens that ovulate but fail to conceive have an interoestrous interval of approximately 50 days (luteal phase is 50 days)
mated queens that become pregnant have a luteal phase of about 65 days
What is the non-pregnant luteal phase described as in the bitch?
pseudopregnancy (after mating or spontaneous ovulation)
Clinical signs = absence of oestrous
Unlike in the bitch, mammary development, lactation and behavioural changes are NOT a feature of pseudopregnancy in the queen (i.e. not due to PRL)
How can oestrous be controlled in the cat?
OVH
HORMONES: hCG, androgens, progesterone
Outline hCG treatment in cats
Induces ovulation and delay subsequent calling because Queen goes through period of false pregnancy
Outline androgen treatment in cats
androgenic anabolic steroids cna be used faily to postpone calling by giving daily oral doses about 30 days before anticipated oestrous - induces masculinsation
Outline progesterone treatment in cats
PREVENTION - given as soon as signs of calling, suppress the call and prevention of conception should mating occur
TEMPORARY POSTPONEMENT: given during anoestrous will postpone that would follow naturally
PERMANENT POSTPONEMENT: repeat doses given during anoestrous
Only orally administered progestagens are suitable - high doses for a short time (commencing when signs of calling are seen) will result in the queen stopping exhibiting signs of sexual behaviour.
How can you hormonally control reproduction in the dog and tom?
you can use androgens or anti-androgens to manipulate the system although you tend not to.
Outline the bitch’s cycle
single very long cycle followed by physiological anoestrous. The dog has no luteolytic mechnaims and the length of the cycle is longer than the length of gestation. multiple ovulations.
Outline the Queen’s cycle
induced ovulator, highly variabe follicular phase, mating induced luteal phase that is known as pseudo-pregnancy if the mating is infertile
