Intracellular pH change does not appear as a prerequisite for triggering activation of Barnea candida (Mollusca, Pelecypoda) oocytes.
Barnea candida oocytes, exposed to excess KCl, ammonia, or digitonin, exhibit germinal vesicle breakdown (GVBD) and reinitiate meiosis, at least up to first polar body extrusion. While we confirm that KCl- but not ammonia-induced activation required external calcium, our findings that digitonin is effective at any pH from 6 to 8, in the presence of calcium, while the phorbol ester TPA and diacylglycerol fail to reinitiate meiosis, strongly suggests calcium as the main trigger for this process. Preliminary experiments using the fluorescent probes fluorescein diacetate and Quin 2/AM show, moreover, that KCl and ammonia produce both an intracellular calcium surge (30 nM) and a slight alkalinization of the intracellular cytoplasm from 7.84 to 8.05.
Brassard
M
M
Developmental Biology, CNRS, Roscoff, France.
Duclohier
H
H
Moreau
M
M
Guerrier
P
P
D000818:Animals; D049872:Bivalvia / Q000502:physiology*; D005260:Female; D006863:Hydrogen-Ion Concentration; D008297:Male; D009865:Oocytes / Q000502:physiology*; D013084:Sperm-Ovum Interactions