SN-1,2-DIACYLGLYCEROL LEVELS INCREASE IN PROGESTERONE-STIMULATED XENOPUS-LAEVIS OOCYTES

Full‐grown Xenopus laevis oocytes resume meiosis from prophase arrest in response to progesterone stimulation. Recent studies have shown that the tumor promoter, 12‐O‐tetradecanoylphorbol 13‐acetate (TPA), a very potent activator of protein kinase C, can also induce the resumption of meiosis in amphibian oocytes. We have investigated the possibility that sn‐1,2‐diacylglycerol (DAG), the intracellular activator of protein kinase C, may be involved in the pathway normally used by progesterone. We have found that full‐grown oocytes arrested in meiotic prophase contain 48 ± 5 pmoles DAG/oocyte. This level increases within the first 5 minutes following the addition of progesterone and reaches a maximum of 75 ± 10 pmoles following 60 minutes of steroid stimulation. Progesterone induces the up‐regulation of a Na+ /H+ antiport in the plasma membrane of the oocyte causing an increase in pHi following 60 minutes of steroid stimulation. We have found that the addition of 200 μM DAG (1,2‐dioctanoylglycerol, diC8) to the culture medium can cause a partial up‐regulation of this Na+ /H+ pump in the absence of hormonal stimulation. These results suggest that DAG and protein kinase C may be involved in regulating certain aspects of meiotic maturation in progesterone‐stimulated Xenopus oocytes. Copyright © 1990 Wiley‐Liss, Inc., A Wiley Company