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Oocyte Ca2+ spike acquisition during in vitro development of early preantral follicles: influence of age and hormonal supplementation

Published online by Cambridge University Press:  09 April 2002

Odile G. Martins
Affiliation:
Instituto de Histologia e Embriologia, Faculdade de Medicina de Lisboa, Lisbon, Portugal INSERM Unité 355, Maturation Gamétique et Fécondation and IFR 13, Clamart, France
Arlette Pesty
Affiliation:
INSERM Unité 355, Maturation Gamétique et Fécondation and IFR 13, Clamart, France
António Gouveia-Oliveira
Affiliation:
Laboratório de Biomatemática, Faculdade de Medicina de Lisboa, Lisbon, Portugal
António J. Cidadão
Affiliation:
Instituto de Histologia e Embriologia, Faculdade de Medicina de Lisboa, Lisbon, Portugal
Carlos E. Plancha
Affiliation:
Instituto de Histologia e Embriologia, Faculdade de Medicina de Lisboa, Lisbon, Portugal
Brigitte Lefèvre
Affiliation:
INSERM Unité 355, Maturation Gamétique et Fécondation and IFR 13, Clamart, France

Abstract

Calcium signalling is involved in important events in oocytes, such as meiotic competence acquisition. We have previously demonstrated the positive influence of animal age and gonadotropin stimulation in vivo regarding the ability of oocytes recovered from preantral follicles to exhibit calcium spikes. In the present work we determined whether preantral follicle development in vitro also allows oocytes to acquire calcium signalling activity. We also aimed to verify the influence of animal age, FSH + LH and/or insulin on oocyte calcium spike acquisition during preantral follicle culture. Early preantral follicles were isolated from 12-day-old and 1- to 3-month-old F1 hybrid mice and cultured individually for either 2 or 6 days. At the end of the culture period the oocytes were processed for calcium imaging by confocal microscopy. We show that oocytes recovered from cultured preantral follicles exhibit variable calcium spike activity rates, depending on animal age, culture duration and hormonal supplementation. Oocytes recovered from adult animals continue to exhibit calcium spikes, and those recovered from juveniles acquire that activity after culture. Insulin and gonadotropins in combination account for an early and maintained inhibitory effect on calcium signalling acquisition by oocytes. Insulin alone also leads to an early inhibitory effect, which, however, disappears with longer culture periods. Contrary to the complex in vivo situation, the acquisition of calcium signalling by oocytes in a controlled in vitro environment does not seem to be dependent on gonadotropins alone.

Type
Research Article
Copyright
2002 Cambridge University Press

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