OXYGEN REQUIREMENT FOR INVITRO GROWTH AND DIFFERENTIATION OF THE RAT CONCEPTUS DURING ORGANOGENESIS PHASE OF EMBRYO DEVELOPMENT

The relationship between oxygen requirement for respiration and in vitro growth and differentiation of rat embryos of pregnancy day 11 (embryonic age approximately 10.5 days) has been studied in the 'New system' of embryo culture in rotating 60 ml serum bottles. In the culture medium of heat inactivated immediately-centrifuged male rat serum (5 concepti/10 ml) equilibrated with 20-40% O2, 5% CO2, and N2, the embryos grew and differentiated during 24 h of culture apparently identically to the in vivo control embryos during the same period. Under this optimal gas environment, pregnancy day 11 embryos of 14-15 somites grew to 30-31 somites with extensive differentiation of brain and sensory organs, hepatic primordia, heart and circulatory systems. DNA, RNA and protein contents in the cultured embryos increased 5-7 fold from the initial values. Heparinized plasma, with a gas environment identical to that of serum, was a poor medium. Lower O2 tension in the culture media with 5 and 10% O2 was detrimental to growth and normal differentiation of concepti, significantly decreasing the nucleic acid and protein synthesis of the embryos.