title: IGF-I slightly improves nuclear maturation and cleavage rate of bovine oocytes exposed to acute heat shock in vitro.
abstract: An in vitro model of embryo production was used to examine the effects of insulin-like growth factor (IGF)-I on maturation and developmental competence of oocytes exposed to heat shock. Cumulus-oocyte complexes were matured at 38.5°C or exposed to acute heat shock (HS; 41.5°C), with or without 100 ng/ml IGF-I, for 22 h through in vitro maturation. The experimental groups were control (C), C + IGF-I, HS, and HS + IGF-I. Oocytes were fertilized at the end of maturation, and the proportion of cleaved embryos was recorded 44 h later. HS during maturation increased the proportion of TUNEL-positive oocytes (P < 0.05). HS did not have any effect on cortical granule translocation but impaired resumption of meiosis, expressed as a decreased proportion of oocytes with nuclei in metaphase I (P < 0.05) and metaphase II (MII; P < 0.05). HS decreased the proportion of oocytes that cleaved (P < 0.05), in particular those oocytes that further developed to 4-cell-stage embryos (P < 0.05). IGF-I alleviated, to some extent, the deleterious effects of HS on the oocytes as reflected by a reduced proportion of TUNEL-positive oocytes (P < 0.03). While not significant, IGF-I tended to increase the proportion of MII-stage oocytes (P < 0.08) and 4-cell-stage cleaved embryos (P < 0.06). Further examination is required to explore whether IGF-I also affects the developmental competence of oocytes exposed to HS.
authors.affiliation: Heilongjiang Academy of Agricultural Sciences,Harbin,China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Meiyu
authors.affiliation: Heilongjiang Academy of Agricultural Sciences,Harbin,China.
authors.forename: Di
authors.initials: D
authors.lastname: Liu
authors.affiliation: Department of Animal Sciences,Robert H. Smith Faculty of Agriculture,Food and Environment,the Hebrew University,Rehovot 76100,Israel.
authors.forename: Zvi
authors.initials: Z
authors.lastname: Roth
mesh_terms: D000818:Animals; D017209:Apoptosis; D002417:Cattle; D002467:Cell Nucleus; D002478:Cells, Cultured; D002970:Cleavage Stage, Ovum / Q000166:cytology; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D005260:Female; D005307:Fertilization in Vitro; D018869:Heat-Shock Response / Q000502:physiology*; D059471:In Vitro Oocyte Maturation Techniques; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D008297:Male; D009865:Oocytes / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*
chemical_list: D007334:Insulin-Like Growth Factor I
keywords: Bovine; Cleavage rate; Heat shock; IGF-I; Oocyte maturation