Intracellular CA2+ response of rabbit oocytes to electrical stimulation

✍ Scribed by Rafael A. Fissore; James M. Robl

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 873 KB
• Volume: 32
• Category: Article
• ISSN: 1040-452X
• DOI: 10.1002/mrd.1080320103

✦ Synopsis

Abstract

Electrical stimulation is known to cause activation in mammalian oocytes, possibly by eliciting an elevation in intracellular calcium (Ca^2+^). This study reports intracellular Ca^2+^ concentrations in mature rabbit oocytes using the Ca^2+^ indicator fura‐2. Calcium levels were determined prior to, during, and after the administration of an electrical pulse (3.6 kV/cm for 60 μsec). Baseline Ca^2+^ levels ranged from 30 to 90 nM. The intracellular Ca^2+^ transient evoked by a pulse, peaked at 11 sec, was highly variable in amplitude (40–300 nM) and returned to prepulse levels within 300 sec. Electrically stimulated oocytes did not exhibit repetitive Ca^2+^ transients. The size of the cytoplasmic Ca^2+^ rise was influenced by the duration of the pulse, the field strength and the concentrations of external Ca^2+^ (P < 0.05). Oocytes electrically stimulated in the presence of 100 μM CaCl~2~, which evoked Ca^2+^ transients with a mean magnitude of 120 nM, activated at a higher rate (P < 0.05) than oocytes stimulated in the presence of either higher or lower levels of external Ca^2+^. Although oocytes electrically shocked at 16–18 hr after administration of human chorionic gonadotropin (hphCG) activated at a lower rate than oocytes stimulated at 22–24 hphCG (P < 0.05), their intracellular Ca^2+^ response to the pulse was similar (P < 0.05). These results indicate that electrical pulse parameters and extracellular Ca^2+^ concentrations can be used to modulate intracellular Ca^2+^ levels and optimize oocyte activation rates. Furthermore, the data suggest that as the oocyte ages it becomes more responsive to a given intracellular Ca^2+^ elevation. © 1992 Wiley‐Liss, Inc.