The rapid transient decrease of sn-1,2-diacylglycerol in progesterone-stimulated Xenopus laevis oocytes is the result of an ethanol artifact.

Full-grown Xenopus laevis oocytes resume meiosis (meiotic maturation) in response to progesterone stimulation. Three studies have shown that sn-1,2-diacylglycerol (DAG), the intracellular activator of protein kinase C, may be involved in this process (Wasserman et al., J. Exp. Zool. 255, 63-71, 1990; Varnold and Smith, Development 109, 597-604, 1990; Stith et al., J. Cell Physiol. 149, 252-259, 1991). Two of these studies (Varnold and Smith, 1990; Stith et al., 1991) found a rapid, but transient decrease in the levels of DAG of approximately 25 to 30% within 5 to 30 sec following the addition of progesterone to the oocytes. We have investigated this rapid decline in oocyte DAG. We also found a 20 to 34% decrease in DAG/oocyte within the first 5 to 40 sec following the addition of steroid to the culture medium. However, a similar rapid and transient decrease in oocyte DAG levels was also observed in response to ethanol. Ethanol is used as the vehicle to deliver progesterone to the oocyte culture medium. Therefore, the rapid transient decline in DAG appears to be an artifact of ethanol perturbing the production and/or turnover of DAG within the oocyte and not a physiological response of the oocyte to progesterone.