addition, Na/K regulates the accumulation of fluid in the blastoceole (Watson and

Barcroft, 2001) as well as the formation of tight junctions during blastocyst expansion

(Violette et al., 2006). Such differences in mRNA for Dc II and Na/K may indicate that

IGF-1 treated embryos were at a more advanced stage of blastocyst expansion than

controls even though all embryos were similar in terms of gross morphology. In addition,

IGF-1 treated embryos may possess a more effective TE with respect to ion and water

movement.

 Compared to embryos produced following superovulation, embryos produced in

vitro under sub-optimal culture conditions have an increased abundance of Hsp70 mRNA

(Wrenzycki et al., 2001a; Lazzari et al., 2002; Sagirkaya et al., 2006). In the present

study, IGF-1 reduced Hsp70 transcript abundance. One possibility for this finding is that

IGF-1 makes embryos more resistant to one or more stresses associated with culture.

Treatment of cultured embryos with IGF-1 reduced the effect of hydrogen peroxide

(Kurzawa et al., 2002) and heat shock (Jousan and Hansen, 2004, 2006).

 One of the actions of Hsp70 is to block apoptosis (Garrido et al., 2001, 2003).

The fact that Hsp70 transcripts were reduced by IGF-1 implies that effects on Hsp70

synthesis are not involved in the anti-apoptotic effects of IGF-1 on apoptosis induced

spontaneously during culture (Herrler et al., 1998; Lighten et al., 1998; Byrne et al.,

2002a; Fabian et al., 2004) or by ultraviolet radiation (Herrler et al., 1998), tumor

necrosis factor a (Byrne et al., 2002a), or heat shock (Jousan and Hansen, 2004). There

was also no effect of IGF-1 on transcript abundance for the anti-apoptotic gene, Bcl.

Moreover, relative abundance of transcripts for the pro-apoptotic gene Bax was increased

by IGF-1. This is somewhat surprising given that increased abundance of Bax might