Molecular Human Reproduction, Vol. 7, No. 2, 129-135,
February 2001
© 2001 European Society of Human Reproduction and Embryology
Ovary and oogenesis |
Effect of different FSH isoforms on cyclic-AMP production by mouse cumulus–oocyte–complexes: a time course study
1 Laboratory of Reproductive Biology, University Hospital of Copenhagen, Copenhagen, Denmark, and 2 Research Unit in Reproductive Medicine, Hospital de Ginecobstetricia `Luis Castelazo Ayala', Instituto Mexicano del Seguro Social, Mexico DF, Mexico
Abstract
The ability of different isoforms of follicle stimulating hormone (FSH) to induce accumulation of cAMP in cultured mouse cumulus–oocyte–complexes (COC) was evaluated in a time course study. Using isoform fractions representing less acidic (pI 6.43–5.69), mid-acidic (pI 5.62–4.96) and acidic (pI 4.69–3.75) isoforms, the accumulation of cAMP was monitored after an exposure time of 0, 5, 10, 15, 30, 60, 120 and 180 min. In addition, cAMP production was monitored for 0, 5, 10, 15 and 30 min following a 5 min exposure to FSH isoform fractions. Based on FSH measurements using radioimmunoassays, the less and mid-acidic isoforms caused almost twice as much cAMP to be accumulated than the acidic isoform fraction, thereby confirming an enhanced biological activity of FSH isoforms with a isoelectric point (pI) of >5.0. For all isoform fractions, maximal accumulation of cAMP was achieved after 30 min of exposure, after which the production declined to background levels. After a 5 min exposure to isoform fractions, levels of cAMP were significantly higher in the less acidic isoform fractions, but after isoform removal, the decline in cAMP production to background levels followed a similar time course. The results demonstrate that FSH isoforms with a pI of >5.0 induced significant biological responses within a period of 30 min and that prolonged exposure caused attenuated signal transduction. The present results, set in the context of the pulsatile characteristics of FSH release from the pituitary and the reported half-life of less acidic isoforms of ~35 min, make it conceivable that isoforms with a pI >5.0 actually possess important physiological functions during the periovulatory period.
cAMP/cumulus/oocyte/complexes/FSH/isoforms
Notes
3 To whom correspondence should be addressed at: Laboratory of Reproductive Biology, Section 5712, Juliane Marie Center for Children, Women and Reproduction, University Hospital of Copenhagen, Blegdamsvej 9, DK-2100 Copenhagen, Denmark. E-mail: yding{at}rh.dk
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