ANALYSIS OF R59022 ACTIONS IN XENOPUS-LAEVIS OOCYTES

R59022, a diacylglycerol (DAG) kinase inhibitor, stimulated meiotic ma turation of Xenopus laevis oocytes when applied extracellularly. The t ime course of R59022-induced oocyte maturation was proportional to the concentration of R59022 in the low micromolor range, and the 30 mu M- induced response was as fast or faster than progesterone-induced matur ation. Dose-response analysis yielded an apparent EC(50) for R59022-in duced oocyte maturation of approximately 15 mu M. An increase in total oocyte DAG levels was observed following treatment with 10 mu M R5902 2. Treatment of oocytes with R59022 also resulted in a significant inc rease in intracellular pH similar to the increase observed with proges terone. When various phosphodiesterase (PDE) inhibitors were tested fo r their effects on R59022-induced oocyte maturation, papaverine (a pot ent nonselective inhibitor of PDE) and CI-930 (a selective PDE III inh ibitor) were observed to significantly inhibit the R59022-stimulated r esponse. The sensitivity of R59022-induced oocyte maturation to inhibi tion by papaverine was intermediate between the sensitivities of the I GF-1- or progesterone-induced responses. Treatment of oocytes with R59 022 did not significantly affect the level of oocyte PDE activity meas ured in vivo, suggesting that elevated levels of DAG may parallel obse rved increases in PDE but do not directly lead to a stimulation of PDE . The time course for stimulation of ribosomal S6 kinase activity by R 59022 followed the pattern for stimulation by progesterone rather than IGF-1. Treatment of isolated membranes with R59022 resulted in inhibi tion of membrane-associated adenyl cyclase activity that was not mimic ked by DAG analogs. Thus, in addition to elevating oocyte levels of DA G, R59022 also has steroid-like actions. (C) 1996 Wiley-Liss, Inc.