Human menopausal gonadotropin induces ovulation in sheep, but embryo recovery after prostaglandin F2alpha synchronization is compromised by premature luteal regression.
Using pregnant mares' serum gonadotropin (PMSG) and follicle stimulating hormone (FSH-P) as conventional gonadotropins, human menopausal gonadotropin (hMG) was tested for its comparative ability to induce multiple ovulations in sheep. Estrous cycles were synchronized using either prostaglandin F2alpha (PGF2alpha) or progestogen (MAP)-impregnated pessaries. During the mid-luteal phase, control ewes received serial saline injections, whereas test females (which also served as embryo donors) received either a single PMSG injection (1200 IU) or serial injections of FSH-P (total, 21 mg) or hMG (total, 1350 IU) over 3.5 d. These sheep were naturally mated and artificially inseminated (AI) in utero. Number of CL and transferable-quality embryos 5 d after AI was greater (P<0.05) in FSH-P-and hMG-treated donors than in PMSG-treated ewes. The lower number of transferable-quality embryos produced by PMSG-treated donors was attributed to a reduced (P<0.05) fertilization rate compared with that of the other treatment groups. There were no differences (P>0.05) in daily circulating estradiol-17beta and progesterone concentrations among the gonadotropin treatment groups. Gonadotropin-treated ewes demonstrated estrus approximately 24 h earlier than control ewes and, therefore, exhibited an accelerated estradiol-17beta surge and rise in circulating progesterone. Progesterone production in gonadotropin-treated ewes was also more variable than in the controls; this was due, in part, to premature luteal regression which occurred in 4 of 10 PMSG-, 3 of 10 FSH-P- and 6 of 10 hMG-treated ewes also given PGF2alpha. Ewes with prematurely regressing CL experienced transient luteal tissue development within 4 d of ovulation and produced no embryos. Overall results 1) demonstrate that serial administration of hMG induces multiple ovulations in sheep comparable to FSH-P, and 2) suggest that PGF2alpha treatment during ovulation induction adversely affects newly formed luteal tissue compromising subsequent embryo recovery.
Schiewe
M C
MC
National Zoological Park, Smithsonian Institution, Washington, DC 20008, USA.
Howard
J G
JG
Goodrowe
K L
KL
Stuart
L D
LD
Wildt
D E
DE