FSH and LH Preparations

Effective ovarian stimulation requires knowledge of the basic concepts of follicular dynamics as well as an understanding of the respective roles of FSH and LH in regulating follicular development and ovulation. FSH stimulates follicle development by interacting with specific receptors on granulosa cells, inducing increased division of granulosa cells and aromatase activity as well as inducing expression of key genes involved in follicle maturation and the formation of LH receptors. Such receptors are essential for completion of follicle maturation and to allow ovulation to occur in response to the preovulatory surge of LH. Although recombinant bovine FSH has been used to superovulate cattle, there appears to be no technical advantage to its application in this species, where hormone cost is an important consideration. However, as noted by some observers, a recombinant product does not carry the disease risks that may be a serious consideration with pituitaries.[4] In the mare, FSH is species-specific; for that reason, equine preparations of this hormone are likely to be most effective in inducing superovulation.

Early work on superovulation in farm mammals involved comparisons between PMSG and FSH-rich pituitary extracts. Evidence favors the use of FSH, in terms of superovulatory response and embryo yield. Serum gonadotropin, due to its long biological half-life, has undesirable carry-over effects rarely found with pituitary preparations, which have a short half-life. The prolonged half-life of PMSG results in unovulated follicles secreting estradiol, leading to a disturbed

Table 1 Methods used to induce multiple ovulations in different species

Species

Superovulation protocols

Cattle and buffalo

Sheep and goat

Horse

Deer

Camelids

Human

FSH administered on days 8 12 of the estrous cycle. FSH treatment (4 days) initiated one day after follicle ablation or four days after estradiol/progesterone (to synchronize follicular wave emergence)

FSH administered after a period of progestagen treatment. Prostaglandin F2 a given to regress cyclical corpus luteum

A single dose of PMSG at the start of the follicular phase of the estrous cycle (days 15 16) followed by HCG after 3 4 days.

Equine FSH administered daily for 6 days during mid diestrus or late diestrus/early estrus.

12 day progestagen treatment with FSH administered twice daily for final four days. Use a combination of gonadotropin and PGF2 a either during an induced luteal phase (GnRH/HCG) or after a simulated luteal phase (using progestagen). Downregulation of pituitary with GnRH; simultaneous administration of FSH (recombinant or urinary preparations); follicle growth monitored and HCG given to induce ovulation.

hormonal balance. In more recent times the emphasis has been with pituitary preparations having a well-defined FSH and LH content, such as Folltropin-V (Bioniche Canada, Inc.), containing a low level (20%) of LH, or Pluset (Laboratories~Calier, S.A.), containing equal concentrations of FSH and LH.[5]

0 0

Post a comment