Produção in vitro de embriões e expressão gênica de IGF-I e IGF-II em embriões de fêmeas bovinas da raça nelore submetidas a administrações de somatotropina recombinante bovina

Abstract

In vitro production of bovine embryos (IVP) is a tool that serves to increase reproductive potential of females considered exceptional, especially, as an instrument to accelerate the progress of animal selection programs. In order to improve results, exogenous synthetic hormones are being used routinely in the animal reproduction industry. Currently there is a research using recombinant bovine somatotropin (rbST), as a substance that causes the increase in receptors for insulin-like growth factor (IGF). Both IGFs type I and type II and its receptors (IGF-IR and IGF-IIR) are expressed in in vitro produced bovine and ovine oocytes and embryos from which one can prove the close relation of IGF system with the IVP. Researches have proven a trend in oocyte quality improvement in animals treated with rbST, as well as increased fertilization rate and embryo quality improvement. This experiment aimed to study the effect of rbST on quantity and quality of in vivo aspirated oocytes, embryo production and gene expression of IGF-I and IGF-II in vitro produced embryos of bovine females of Nelore breed. Five cows were treated with two administrations of 2mL of saline solution as a placebo, with an interval of 14 days between them, being the first administration performed 19 and the second 5 days before follicular aspirations; 30 days after these aspirations, in crossover system, same protocol was used in these five animals being, in this case, the saline solution replaced by 500mg of rbST in order to compare treatments. It was held to IVP of oocytes recovered from this research, being all the steps that involve this process evaluated with subsequent achievement of polymerase chain reactions in real time (qPCRs) for gene expression of IGF-I and IGF-II in the blastocysts produced in the experiment. No difference was observed on quantity and quality of aspirated oocytes in vivo, embryo production and gene expression of IGF-I and IGF-II in vitro produced embryos of bovine females of Nelore breed under the influence of rbST.