Involvement of purines and phosphoinositides in spontaneous and progesterone-induced nuclear maturation of Bufo arenarum oocytes.
Although progesterone is the established maturation inducer in amphibia, it has been demonstrated that Bufo arenarum oocytes resume meiosis with no need of an exogenous hormonal stimulus if deprived of their enveloping follicle cells, a phenomenon called "spontaneous maturation." The present studies were designed to evaluate the participation of purines and phosphoinositides in the spontaneous and progesterone-induced maturation in Bufo arenarum full-grown oocytes. The presented data demonstrate that high intracellular levels of purines such as cAMP or guanosine can inhibit both spontaneous and progesterone-induced maturation in full-grown denuded Bufo arenarum oocytes. Moreover, the fact that the mycophenolic acid was able to induce maturation in denuded oocytes obtained during the nonreproductive period in a manner similar to that of the progesterone and also to increase the percentages of spontaneous maturation suggests that in Bufo arenarum, inosine monophosphate dehydrogenase inhibition is an important step in the resumption of meiosis. Inhibition of the phosphatidylinositol 4,5 bisphosphate hydrolysis by treatment of denuded oocytes with neomycin totally blocks spontaneous and progesterone-induced maturation, suggesting that the products of this hydrolysis (1,2 diacylglycerol and inositol 1,4,5 trisphosphate) may be involved in the maturation process of Bufo. In addition, our results indicate that the activation of protein kinase C is also involved in both types of maturation.
Zelarayán
L
L
Departamento de Biología del Desarrollo, San Miguel de Tucumán, Argentina.
Oterino
J
J
Sánchez Toranzo
G
G
Bühler
M I
MI
D019297:2,4-Dinitrophenol / Q000494:pharmacology; D000818:Animals; D002022:Bufo arenarum / Q000502:physiology*; D000242:Cyclic AMP / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D006151:Guanosine / Q000494:pharmacology*; D007168:IMP Dehydrogenase / Q000037:antagonists & inhibitors; D009173:Mycophenolic Acid / Q000494:pharmacology*; D009355:Neomycin / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology; D011374:Progesterone / Q000494:pharmacology; D012621:Seasons; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D004791:Enzyme Inhibitors; D006151:Guanosine; D011374:Progesterone; D000242:Cyclic AMP; D007168:IMP Dehydrogenase; D009173:Mycophenolic Acid; D009355:Neomycin; D013755:Tetradecanoylphorbol Acetate; D019297:2,4-Dinitrophenol