Sodium chloride, osmolyte, and osmolarity effects on blastocyst formation in bovine embryos produced by in vitro fertilization (IVF) and cultured in simple serum-free media.

PURPOSE

A simple serum-free medium (KSOM), relatively low in NaCl concentration, has been developed for culturing mouse zygotes produced in vivo. The present studies were designed to test modifications of this medium to establish optimal conditions for culture of bovine embryos produced in vitro.

METHODS

Embryos were produced by standard in vitro fertilization procedures. They were cultured for 6 days in media varying in NaCl concentration and osmolarity with and without osmolytes, betaine or inositol.

RESULTS

Increasing the NaCl concentration from 95 to 108.5 and 122 mM decreased blastocyst formation (P < 0.05). Partial substitution of NaCl by sorbitol indicated that both NaCl concentration and osmolarity were important. Neither betaine nor inositol protected the embryos against high concentrations of NaCl.

CONCLUSIONS

The concentration of NaCl should not be higher than 95 mM and the total osmolarity of the medium should be between 250 and 270 mosmol.