a Department of Population Health &
Reproduction, School of Veterinary Medicine, University of California, Davis,
California 95616
b Animal Physiology Department, Veterinary School, Universidad
Complutense de Madrid, 28040 Madrid, Spain
c Department of Animal Reproduction, Faculdade de Veterinaria,
Universidade Federal de Pelotas, RS 96010-900, Brazil
d Animal Reproduction Laboratory, Temperate Climate Research
Corporation, EMBRAPA, BR 392 Km 78 Cx. P. 403 Pelotas, RS 96001-970, Brazil
e Department of Animal Science, University of California, Davis,
California 95616
ABSTRACT
The effects of insulin-like growth factor-I (IGF-I) and its interaction
with gonadotropins, estradiol, and fetal calf serum (FCS) on in vitro
maturation (IVM) of equine oocytes were investigated in this study.
We also examined the role of IGF-I in the presence or absence of
gonadotropins, estradiol, and FCS in parthenogenic cleavage after
oocyte activation with calcium ionophore combined with
6-dimethylaminopurine (6-DMAP), using cleavage rate as a measure of
cytoplasmic maturation. Only equine cumulus-oocyte complexes with
compact cumulus and homogenous ooplasm (n = 817) were used. In
experiment 1, oocytes were cultured in TCM-199 supplemented with BSA,
antibiotics, and IGF-I at 0 (control), 50, 100, 200 ng/ml, at 39°C
in air with 5% CO2, 95% humidity for 36 or 48 h. In
experiment 2, oocytes were cultured with FSH, LH, estradiol, and FCS
with IGF-I at the concentration that promoted the highest nuclear
maturation rate in experiment 1. In experiment 3, oocytes from the
three experimental groups (IGF-I; hormones; and IGF-I + hormones)
were chemically activated by exposure to calcium ionophore followed
by culture in 6-DMAP. In experiment 1, IGF-I stimulated equine oocyte
maturation in a dose-dependent manner with the highest nuclear
maturation rate at a concentration of 200 ng/ml. No significant
effect of IGF-I on nuclear maturation was observed in experiment 2.
In experiment 3, a significant difference in cleavage rate was observed
between the hormone + IGF-I group (15 of 33; 45.4%) compared with
IGF-I (10 of 36; 27.8%) and hormone (4 of 31; 12.9%) alone (P
< 0.05). These results demonstrated that IGF-I has a positive
effect on nuclear maturation rate of equine oocytes in vitro. The
addition of IGF-I to an IVM medium containing hormones and FCS did
not increase nuclear maturation, but resulted in a positive effect on
cytoplasmic maturation of equine oocytes measured by parthenogenic
cleavage.
FOOTNOTES
First decision: 7 February 2001.
1 This project was supported in part by Club Hipico La Silla, Monterey, Mexico, and by Center for Equine Health with funds provided by the Oak Tree Racing Association, the State of California parimutuel fund, and contributions by private donors. G.C. is a research fellow recipient of CAPES/MEC, Brazil. Part of this work was presented as a poster at the International Embryo Transfer Society Meeting (IETS), Omaha, NE, 13–16 January 2001.
2 Correspondence: Irwin K.M. Liu and Gustavo F. Carneiro, Department of Population Health and Reproduction, School of Veterinary Medicine, 1114 Tupper Hall, University of California, Davis, CA 95616. FAX: 530 752 4278; ikliu@ucdavis.edu and gfcarneiro@ucdavis.edu
|
If you have come to this page from an outside location click here to get back to mindfully.org |