Strontium-induced rat egg activation.
Parthenogenetic agents that evoke cytosolic calcium concentration ([Ca2+]i) oscillations similar to those evoked by sperm, mimic fertilization more faithfully than agents that trigger a single [Ca2+]i transient. Strontium chloride (SrCl2) binds to and activates the Ca2+-binding site on the inositol 1,4,5-trisphosphate receptor and evokes [Ca2+]i oscillations. Although SrCl2 has been reported to activate mouse eggs, little is known regarding the pattern of the [Ca2+]i oscillations it evokes in rat eggs and their effect on the early events of egg activation: cortical granule exocytosis (CGE) and completion of meiosis (CM). In the current study we investigated the effect of various concentrations of SrCl2 (2, 4 or 6 mM) on [Ca2+]i, by monitoring [Ca2+]i oscillations in fura-2-loaded rat eggs. Treatment with 2 mM SrCl2 was optimal for inducing the first [Ca2+]i transient, which was similar in duration to that triggered by sperm. However, the frequency and duration of the subsequent [Ca2+]i oscillations were lower and longer in SrCl2-activated than in sperm-activated eggs. The degree of CGE was identical in eggs activated by either sperm or SrCl2, as assessed by semi-quantitative immunohistochemistry combined with confocal microscopy. Evoking 1, 2 or 10 [Ca2+]i oscillations (8, 15 or 60 min in SrCl2 respectively) had no effect on the intensity of fluorescent CGE reporter dyes, while 60-min exposure to SrCl2 caused a delay in CM. Our results demonstrate that SrCl2 is an effective parthenogenetic agent that mimics rat egg activation by sperm, as judged by the generation of [Ca2+]i oscillations, CGE and CM.
Tomashov-Matar
R
R
Cell and Developmental Biology and Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Ramat-Aviv 9978 Tel-Aviv, Israel.
Tchetchik
D
D
Eldar
A
A
Kaplan-Kraicer
R
R
Oron
Y
Y
Shalgi
R
R
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D005260:Female; D005307:Fertilization in Vitro; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008297:Male; D018613:Microscopy, Confocal; D009865:Oocytes / Q000187:drug effects* / Q000378:metabolism; D009866:Oogenesis / Q000187:drug effects*; D010312:Parthenogenesis / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D013324:Strontium / Q000494:pharmacology*
D007476:Ionophores; D015759:Ionomycin; C025700:strontium chloride; D002118:Calcium; D013324:Strontium