Respiratory activity of oocytes isolated from ovarian follicles of the rat.

In order to study substrate dependent respiration oocytes were isolated from antrum follicles obtained from ovaries of prepubertal rats. The oocytes used were either surrounded by 1 to 3 layers of granulosa cells (oocyte + corona radiata), or mechanically denuded from surrounding cells (denuded oocytes). By use of Cartesian micro-diver technique the respiratory rate could be determined in single oocyte + corona radiata cell complexes or in samples of a few denuded oocytes. The oocytes were incubated either in an isotonic Tris-HCL buffer or in a hypotonic phosphate buffer. The rate of respiration was determined without addition of exogenous substrate and with addition of different substrates in varying concentrations. Cellular respiration was linear 2-4 h both in absence and presence of substrate. Both types of oocyte preparations were unable to utilize glucose as substrate. Lactate stimulated slightly the respiration of the denuded oocyte while pyruvate and oxalcetate increased markedly the respiratory activity of both types of oocyte preparations. Succinate had an influence on the oocyte + corona radiata only when the hypotonic medium was used while it was easily utilized in both media by the denuded oocyte. In a preliminary series of experiments the in vitro influence of bovine lutienizing hormone (LH) on the cellular respiration was studied. Both in presence and absence of corona radiata a significant decrease in oxygen uptake was registered, consistently appearing within 30 min after the addition of the hormone. As the relationship of the phenomenon to ovum maturation was not studied, the possible biological meaning remains to be elucidated.