FSH-induced resumption of meiosis in mouse oocytes: effect of different isoforms.
The ability of different isoforms of follicle stimulating hormone (FSH) to induce the resumption of meiosis in cultured mouse oocytes was evaluated. Oocytes were cultured in the presence of hypoxanthine to prevent spontaneous resumption of meiosis. Using serial dilutions of the isoform fractions representing less acidic isoforms (pI 6. 43-5.69), mid-acidic (pI 5.62-4.96) and acidic (pI 4.69-3.75), the concentration which caused 50% of the oocytes to resume meiosis and undergo germinal vesicle breakdown (GVBD) after a culture period of 24 h (i.e. ED(50%) GVBD) was determined. The FSH concentration of the isoform fractions was determined by radioimmunoassay, radio-receptor assay or through cAMP release in a Chinese hamster ovary-cell line expressing the human FSH-receptor. Determined by radioimmunoassay, the (ED(50%) GVBD) values were: less acidic 6.4 +/- 0.3 IU/l (mean +/- SD), mid-acidic 6.1 +/- 0.7 IU/l and acidic 12.2 +/- 0.7 IU/l. The less and mid-acidic isoforms were significant lower than the acidic (P < 0.0005). Similar relationships between the isoform fractions were obtained by the two other FSH assays. The results demonstrate that FSH isoforms with a pI of >5.0 induced resumption of meiosis significantly more efficiently than acidic isoforms. Less and mid-acidic isoforms may exert an important physiological function by inducing the resumption of meiosis in oocytes from pre-ovulatory follicles during the mid-cycle gonadotrophin surge.
Laboratory of Reproductive Biology, Section 5712, Juliane Marie Center for Children, Women and Reproduction, University Hospital of Copenhagen, Blegdamsvej 9, DK-2100 Copenhagen, Denmark.
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C
Yding Andersen
L
L
Leonardsen
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A
Ulloa-Aguirre
J
J
Barrios-De-Tomasi
L
L
Moore
A G
AG
Byskov
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D005260:Female; D005640:Follicle Stimulating Hormone / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D007526:Isoelectric Point; D008540:Meiosis / Q000187:drug effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects*; D020033:Protein Isoforms / Q000737:chemistry / Q000494:pharmacology
D020033:Protein Isoforms; D005640:Follicle Stimulating Hormone