title: Oscillations in intracellular free calcium induced by spermatozoa in human oocytes at fertilization.
abstract: Calcium has an important role in the events of egg activation and early preimplantation development. We investigated changes in intracellular calcium concentration in human oocytes at fertilization using the calcium-sensitive photoprotein aequorin. Oocytes were donated for research by patients undergoing in-vitro fertilization treatment in the Department of Obstetrics and Gynaecology. Cumulus cells, and in some cases zonae pellucidae, were removed by appropriate enzyme treatment. Single oocytes were micro-injected with aequorin and incubated in a chamber perfused with pre-equilibrated culture medium in a photomultiplier system. Eleven zona-intact and 15 zona-free oocytes were incubated with sperm, and oocytes from each group were incubated without sperm as controls. Dramatic transient increases in intracellular free calcium concentration were recorded in three zona-intact and seven zona-free oocytes, thought to be the first direct measurements of intracellular changes in human oocytes at fertilization. The amplitude (up to 2.5 microM), duration (120 s) and frequency (every 10-35 min) of these transients were similar in zona-intact and zona-free oocytes. They resemble those recorded in mouse oocytes, which may therefore be a suitable model for biochemical events at human fertilization.
authors.affiliation: Department of Obstetrics and Gynaecology, University of Liverpool, UK.
authors.forename: C T
authors.initials: CT
authors.lastname: Taylor
authors.forename: Y M
authors.initials: YM
authors.lastname: Lawrence
authors.forename: C R
authors.initials: CR
authors.lastname: Kingsland
authors.forename: M M
authors.initials: MM
authors.lastname: Biljan
authors.forename: K S
authors.initials: KS
authors.lastname: Cuthbertson
mesh_terms: D000331:Aequorin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D008297:Male; D013084:Sperm-Ovum Interactions / Q000502:physiology*; D015044:Zona Pellucida / Q000502:physiology*
chemical_list: D000331:Aequorin; D002118:Calcium