Insulin and insulin-like growth factor-I promote rabbit blastocyst development and prevent apoptosis.
Insulin as well as insulin-like growth factor-I (IGF-I) promote early embryo development, and IGF-I binds to the coats of preimplantation rabbit embryos. As the IGF-I receptor is expressed from the morula stage onwards, the embryos are capable of responding to insulin and IGF-I, which is present in the oviductal and uterine secretions that surround them. The embryonic coats were removed to exclude any influence by IGF-I bound to the coats. The in vitro development of such embryos under classical conditions appears to be retarded. Addition of IGF-I (68 pM-6.8 nM) or insulin (68 nM-6.8 microM), however, promotes blastocyst formation. Embryo development under such conditions is not significantly different from that of embryos cultured with intact coats. In contrast, coat-free embryos cultured without IGF-I or insulin supplementation show apoptosis. Because IGF-I stimulates cell proliferation and prevents apoptosis, we investigated whether insulin or IGF-I may act as "survival factors" in preimplantation development. Therefore, apoptosis was induced by slight UV irradiation (254 nm wave length; 11.8 W/m2). Compared to the untreated controls, embryos displaying retarded development or degeneration were increased by 22% and 14%, respectively. Addition of IGF-I or insulin to the culture medium of UV-irradiated embryos improved [3H]thymidine incorporation and blastocyst formation significantly. By immunohistochemistry we could show that addition of insulin (0.68-68 nM) decreased apoptosis and increased cell proliferation in a dose-dependent manner, supporting blastocyst development significantly.
Herrler
A
A
Department of Anatomy and Reproductive Biology, RWTH University of Aachen, 52057 Aachen, Germany. herrler@alpha.imib.rwth-aachen.de
Krusche
C A
CA
Beier
H M
HM
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001755:Blastocyst / Q000187:drug effects / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects; D002462:Cell Membrane / Q000502:physiology; D046508:Culture Techniques; D004622:Embryo, Mammalian / Q000648:ultrastructure; D005314:Embryonic and Fetal Development; D005260:Female; D007328:Insulin / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D011817:Rabbits; D014466:Ultraviolet Rays
D007328:Insulin; D007334:Insulin-Like Growth Factor I