Premium
Aging‐related changes in calcium oscillations in fertilized mouse oocytes
Author(s) -
Igarashi Hideki,
Takahashi Eiji,
Hiroi Masahiko,
Doi Katsuhiko
Publication year - 1997
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/(sici)1098-2795(199711)48:3<383::aid-mrd12>3.0.co;2-x
Subject(s) - oocyte , thapsigargin , biology , human fertilization , endocrinology , ovulation , medicine , oocyte activation , calcium , human chorionic gonadotropin , andrology , extracellular , endoplasmic reticulum , anatomy , biochemistry , microbiology and biotechnology , embryo , hormone
Aging of oocytes, being not fertilized after ovulation for a prolonged time, considerably affects normal development of the fertilized oocyte. We examined effects of the aging on a series of highly repetitive Ca 2+ transients commonly seen in fertilized mouse oocytes (Ca 2+ oscillations). Frequency of Ca 2+ oscillations in the aged oocyte [20 hrs after induction of superovulation by i.p. human chorionic gonadotropin (hCG)] was significantly higher (34.1 ± 5.8 1/hr) than the fresh oocyte (14 hr post‐hCG, 21.8 ± 7.9 1/hr). Rates of rise and fall of individual Ca 2+ transient in the aged oocyte were significantly slower than the fresh oocyte, whereas durations of individual Ca 2+ transients were similar. When extracellular Ca 2+ was raised from 2.04 mM to 5.00 mM, aged oocytes showed significant prolongation of the duration of individual Ca 2+ transient, that resulted in a sustained elevation of intracellular Ca 2+ ([Ca 2+ ] i ) in 33% of the aged oocyte. Transient increase in [Ca 2+ ] i by photolysis of a caged Ca 2+ , Nitr‐5, injected into cytoplasm was completely restored in the fresh oocyte [fluorescence intensity of [Ca 2+ ] i indicator dye Fluo‐3 (F 480 ) returned to 97 ± 2% of the control level, time constant = 37 ± 9 sec]. In contrast, in the aged oocyte, restoration of F 480 following Nitr‐5 photolysis was incomplete (115 ± 12% of the control) and slow (time constant = 64 ± 23 sec). Because inhibition of the Ca 2+ pump of the endoplasmic reticulum (ER) by 5 μM thapsigargin almost completely inhibited restoration of F 480 following Nitr‐5 photolysis in the fresh oocyte, we conclude that the aging‐related changes in Ca 2+ oscillations may be accounted for by dysfunction of intracellular Ca 2+ regulation, presumably of the Ca 2+ pump of the ER. Mol. Reprod. Dev. 48:383–390, 1997. © 1997 Wiley‐Liss, Inc.