[Study of energy metabolism in the oocyte by cycling method]

A microassay method sensitive enough to analyze the enzyme activities in one oocyte was developed using enzymatic cycling for amplifying the reaction product to 10,000 fold. An oil-well technique was applied in the assay for achieving the reaction in the medium as small as 1.0 to 5.0 microliter. Immature Wistar rats were superovulated by PMS-hCG administration. Oocytes were collected by the puncture of the follicle and the flushing of the tube. They were freeze-dried after washing to remove cumulus cells. The dry weight was about 50ng on a quartz fiber fishpole balance. The activity of hexokinase was 1.75 +/- 0.14 picomol/oocyte/hr corresponding to one-tenth of the ovarian homogenate as control, indicating low capacity of glucose utilization in the oocyte. The activities of G6PD, LDH, and MDH were 8.41 +/- 0.34, 35.7 +/- 2.89. 11.1 +/- 2.5 picomol/oocyte/min, respectively. High activity of G6PD suggests the pentose phosphate shunt concerned with steroidogenesis is active in the oocyte. HCG increased the activities of hexokinase and MDH and decreased that of G6PD. The activity of LDH remained unchanged.