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Calcium elevation in sheep cumulus‐oocyte complexes after luteinising hormone stimulation
Author(s) -
Mattioli Mauro,
Gioia Luisa,
Barboni Barbara
Publication year - 1998
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(199807)50:3<361::aid-mrd13>3.0.co;2-7
Subject(s) - biology , oocyte , calcium , stimulation , endocrinology , hormone , medicine , microbiology and biotechnology , embryo
We investigated Ca 2+ levels in intact cumulus‐oocyte complexes (COCs) on exposure to peak levels of luteinising hormone (LH). Specific preparations were used where cumulus corona cells were loaded with a membrane‐permeant Ca 2+ ‐sensitive dye (FLUO‐3AM), whereas the oocyte was injected directly with the nonpermeant form of the dye (FLUO‐3). After exposure to LH, cumulus and corona radiata cells showed distinct rises in intracellular Ca 2+ in 50–200 sec. The pattern of Ca 2+ response varied in the different cells both for the duration of the transients and for their persistence. Interestingly, Ca 2+ elevations were recorded in all the layers of the cumulus mass, including the innermost layer of corona cells, demonstrating the wide diffusion of LH receptors. Following the Ca 2+ raise in somatic cells, an intracellular Ca 2+ elevation also was recorded within the oocyte with a delay of 100–300 sec. The elevation started at the cortex of the oocyte and then spread all over the ooplasm. The addition of verapamil or manganese chloride did not prevent LH‐induced Ca 2+ elevation in the COC, whereas mechanical uncoupling of cumulus cells from the oocyte prevented any Ca 2+ response within the oocyte. The results indicate that cumulus‐corona cells are capable of transducing LH message by rising intracellular Ca 2+ and show that this signal is rapidly transferred into the oocyte through gap junctions. This may result from the direct diffusion of Ca 2+ or its putative releaser IP3 from cumulus cells to the oocyte. Mol. Reprod. Dev. 50:361–369, 1998. © 1998 Wiley‐Liss, Inc.