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This Article Full Text Full Text (PDF) All Versions of this Article: 70/1/99    most recent biolreprod.103.021949v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ginther, O.J. Articles by Kot, K. Search for Related Content PubMed PubMed Citation Articles by Ginther, O.J. Articles by Kot, K. Agricola Articles by Ginther, O.J. Articles by Kot, K.

In Vivo Effects of an Intrafollicular Injection of Insulin-Like Growth Factor 1 on the Mechanism of Follicle Deviation in Heifers and Mares¹

Eutheria Foundation,³ Cross Plains, Wisconsin 53528 Department of Animal Health and Biomedical Sciences,⁴ University of Wisconsin, Madison, Wisconsin 53706

In cattle and mares, free insulin-like growth factor 1 (IGF-1) is higher in the future dominant follicle (F1) than in the future largest subordinate follicle (F2) before deviation in diameter or selection is manifested between the two follicles. The effect of IGF-1 on other follicular-fluid factors and on the destiny of F2 were studied in two experiments in each species, using a total of 40 heifers and 42 mares. An injection of IGF-1 was made into F2 at the expected beginning of deviation (heifers, F1 8.5 mm; mares, F1 20.0 mm; Hour 0). In heifers, follicular fluid was taken from F2 at Hours 3, 6, 12, or 24; each heifer was sampled only once. In mares, sequential F2 samples were taken from each mare at Hours 0, 6, and 24 or at Hours 12 and 24. Transvaginal ultrasound guidance was used for treatment and sample collection. In heifers, IGF-1 treatment of F2 stimulated the secretion of estradiol (P < 0.05) between Hours 3 and 6 and androstenedione (P < 0.05) between Hours 3 and 12. In F2 of control heifers, estradiol decreased (P < 0.05) and androstenedione did not change significantly. In mares, IGF-1 treatment of F2 did not affect the concentrations of estradiol during the 24-h posttreatment period; androstenedione decreased (P < 0.04) in the IGF-1 group and increased (P < 0.006) in the controls. Compared with control mares, the IGF-1 group had higher (P < 0.04) activin-A at Hours 12 and 24 and higher (P < 0.0006) inhibin-A at Hour 24. After ablating F1 at Hour 24 in mares, F2 became dominant and ovulated in more mares (P < 0.0002) in the IGF-1 group (12/14) than in the control group (2/14). These results are consistent with reported temporal relationships among follicular factors during deviation in both species and indicate that IGF-1 plays a key role in controlling the temporal relationships; however, no indication was found that IGF-1 stimulated estradiol production in mares during the 24 h after treatment.

¹ This work was supported by the Eutheria Foundation and by the University of Wisconsin-Madison. Some of these data were presented at the International Embryo Transfer Meeting, Brazil, January 2002.

² Correspondence: O.J. Ginther, Department of Animal Health and Biomedical Sciences, 1656 Linden Dr., University of Wisconsin, Madison, WI 53706. FAX: 608 262 7420; ginther{at}svm.vetmed.wisc.edu

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