Growth hormone priming as an adjunct treatment in superovulatory protocols in the ewe alters follicle development but has no effect on ovulation rate
1998
Joyce, I.M. | Khalid, M. | Haresign, W.
This study investigated the effect of FSH alone and rGH priming followed by FSH treatment on follicle populations, follicular fluid concentrations of components of the IGF system and steroids, and the ovulation rate in sheep. Estrus was synchronized with progestagen sponges. Ewes (n = 10/group) in Group 1 served as untreated controls, while those in Groups 2 to 5 received a standard superovulatory treatment of 1.1 mg im oFSH twice daily for 4 d. In addition, ewes in Group 3 and 5 were administered rGH (15 mg/d, im) for the 7 d prior to FSH treatment. Groups 1, 2 and 3 were sacrificed just prior to the LH surge; Groups 4 and 5 were allowed to ovulate. Daily plasma samples were collected to monitor GH, IGF-1 and insulin levels. All follicles greater than or equal to 1.0 mm from Groups 1, 2 and 3 were counted, and follicular fluid from follicles greater than or equal to 2.5 was assayed for estradiol, testosterone, IGF-1 and IGFBPs. Compared with the control, treatment with rGH+FSH but not FSH alone increased (P<0.001) plasma concentrations of GH, IGF-1 and insulin. The mean number of large- (greater than or equal to 4.5 mm) and medium-sized (2.5 to 4.0 mm) follicles was increased to (P<0.01), and the mean number of small (less than or equal to 2.0 mm) follicles was decreased (P<0.001) by FSH treatment. The mean number of medium-sized (2.5 to 4.0 mm) follicles was further increased (P<0.05) by rGH priming. Estradiol concentration in medium but not in large estrogenic follicles was increased (P<0.05) by rGH priming, whereas testosterone concentration in estrogenic follicles was not altered. Components of the IGF system in medium-sized estrogenic follicles were similar in all treatment groups; however, in large estrogenic follicles rGH increased IGF-1 concentrations (P<0.05) and intensity of the 44-42 kDa IGFBP band (P<0.01). Priming with rGH did not alter superovulatory responses. These results show that rGH priming, when used as an adjucnt to FSH treatment in ewes, alters components of the IGF system in large estrogenic follicles and increases the number and physiological maturity of medium-sized follicles in the ovary; it does not however alter ovulation rate responses.
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