Analysis of mouse oogenesis in vitro. Oocyte isolation and the utilization of exogenous energy sources by growing oocytes

Abstract

A method is described for the dissociation of mouse ovaries and the isolation of oocytes free of somatic cells by agitating pieces of ovary in collagenase and deoxyribonuclease in a calcium and magnesium free salt solution. This method yielded about 50% of the growing oocytes from immature mice. The utilization of exogenously administered ¹⁴C-labelled energy sources by oocytes in various growth stages was determined by measurement of evolved ¹⁴CO₂. Little or no evolution of ¹⁴CO₂ was detected from oocytes of any size incubated in ¹⁴C-glucose, lactate or succinate. The production of ¹⁴CO₂ from ¹⁴C-pyruvate increased logarithmically when plotted against increasing oocyte volume with a plateau occurring after oocytes reached a volume of 65,500 μm³ (50 μ diameter). Thus, the pattern of energy metabolism for oocyte maturation and early egg cleavage, wherein glucose and lactate are not utilized as efficiently as pyruvate, has been established by the earliest stages of oocyte growth.