Addition of melatonin to the maturation medium of bovine oocytes subjected to heat shock: effects on the production rate and quality of blastocysts
Year: 2018
Type: dissertation
Abstract: Heat stress increases the production of free radicals, which contributes to a decrease in the \nquality of oocytes and embryos. Thus, the addition of antioxidants, such as melatonin, to \nthe in vitro maturation medium (IVM), has the potential to reduce damages from high \ntemperatures. Addition of melatonin to the IVM medium of bovine oocytes submitted to heat \nshock on production rates and blastocyst quality was evaluated. Slaughterhouse derived \noocytes were matured under heat shock (12 h at 41.0 \no \nC followed by 12 h at 38.5 \no \nC) in IVM \nmedium without (0M) or with melatonin at 10 \n-12 \n; 10 \n-9 \n; 10 \n-6 \nand 10 \n-3 \nM concentrations. In the \npositive (non-stress) control, oocytes were matured in the absence of melatonin under \nconventional conditions (24 h at 38.5 \no \nC). In the DMSO control oocytes were matured in \nmedium containing 0.46% DMSO (same concentration as the 10 \n-3 \nM treatment), under heat \nshock. Oocytes were randomly assigned to treatments blocked by days of ovarian collection. \nGreater proportions (P <0.05) of embryos with eight or more cells on day 3 of culture (D3) \nwere observed in the 10 \n-3 \n, 10 \n-6 \nand 10 \n-9 \nM melatonin treatments and non-stress control \ncompared to 10 \n-12 \nand 0 M treatments. The proportion of embryos with eight or more cells in \nD3 was higher (P <0.05) in the DMSO control compared to 10 \n-9 \n, 10 \n-12 \ne 0 M groups. \nBlastocyst production on days 7 (D7) and 8 (D8), total number of cells, apoptotic cells to total \ncell ratio and the proportion of apoptotic cells to the inner cell mass (ICM) (P> 0.05) did not \nchange by the addition of melatonin or DMSO to the IVM medium nor by heat shock (0 M vs \nnon-stress control). The 10 \n-6 \nM treatment resulted in a greater proportion (P <0.05) of ICM in \nrelation to total cells compared to 10 \n-9 \n, 10 \n-12 \n, 0 M and DMSO treatments, but did not differ \n(P> 0.05) from the 10 \n-3 \nM treatment and non-stress control. The greater the melatonin \nconcentration the greater the proportion of embryos with eight or more cells in D3 increased \n(P <0.05). The proportion of MCI cells increased from 10 \n-9 \nM, peaking at 10 \n-4 \nM, followed \nby a reduction at 10 \n-3 \nM. In conclusion, the addition of melatonin up to 10 \n-3 \nM in the MIV \nmedium of oocytes under heat shock stimulated embryonic development to the 16-cell stage \nand the proportion of MCI cells was increased by the addition of 10 \n-4 \nM melatonin to the IVM \nmedium.
Author: Lima, Pedro Henriques
Language: English
Subfield: Reproductive Medicine
Field: Medicine
Domain: Health Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W7017340153