Ultrastructural localisation of calcium deposits in pig oocytes maturing in vitro: effects of verapamil.
The culture of pig oocytes in the presence of the calcium channel blocker verapamil (0.02 mM) resulted in the blocking of meiosis at the metaphase I stage, and only a small fraction (about 28%) of the oocytes were able to continue their maturation to the stage of metaphase II. Hence, meiotic maturation in pig oocytes is a calcium-dependent process. After isolation of the pig oocytes from their follicles, the intracellular calcium deposits in the oocyte and granulosa cells, detectable using the combined oxalate-pyroantimonate method, are depleted. The amount of calcium deposits in the oocyte and granulosa cells increased during oocyte meiotic maturation in vitro, especially in the nucleus, mitochondria, vacuoles and cytoplasm. The replenishment of calcium deposits is significantly changed under the effect of verapamil. The increase in calcium deposits in the oocyte nucleus was delayed, a much larger amount of deposits was formed in the mitochondria, and the amount of deposits in the vacuoles was demonstrably smaller. A significant peak in the accumulation of calcium deposits was observed in the cytoplasm of verapamil-treated oocytes after 16 h of in vitro culture. We propose that an altered pattern in the replenishment of calcium deposits can disturb intracellular signalling and prevent the exit of oocytes from the metaphase I stage.
Rozinek
J
J
Department of Veterinary Science, Czech University of Agriculture in Prague, Prague, Czech Republic. rozinek@af.czu.cz
Vanourková
Z
Z
Sedmíková
M
M
Lánská
V
V
Petr
J
J
Rajmon
R
R
Jílek
F
F
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005260:Female; D009865:Oocytes / Q000187:drug effects* / Q000502:physiology / Q000648:ultrastructure*; D013552:Swine; D014700:Verapamil / Q000494:pharmacology*
D002121:Calcium Channel Blockers; D014700:Verapamil; D002118:Calcium