175. EFFECTS OF SPECIES DIFFERENCES ON OOCYTE REGULATION OF GRANULOSA CELL PROLIFERATION
J. Lin A , J. Juengel B and K. McNatty AA School of Biological Sciences, Victorica University of Wellington, Wellington, New Zealand.
B Invermay Agriculture Centre, AgResearch, Dunedin, New Zealand.
Reproduction, Fertility and Development 22(9) 93-93 https://doi.org/10.1071/SRB10Abs175
Published: 6 September 2010
Abstract
The role of oocytes in regulating ovulation quota between species is not fully understood. In sheep, the oocyte-derived growth factors, growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) have profound effects on ovarian follicular development and ovulation-quota. The aim of these studies was to compare the ability of oocytes from sheep (low ovulation-rate) and rat (poly-ovulator) to stimulate radiolabelled thymidine uptake by granulosa cells (GC) both within and between the two species. For these experiments, 32 oocytes denuded of cumulus-cells were co-incubated with 20 000 GC from either species. Rat or sheep oocytes stimulated thymidine uptake by GC from the same species (P < 0.005). Sheep oocytes also stimulated thymidine uptake by rat GC (P < 0.001) but not vice versa. To investigate this further, oocytes and GC were co-incubated with 3.2 µg/mL or 7.6 mg/mL monoclonal antibodies specific to GDF9 or BMP15 respectively and to a hydatids antigen (control). Both sheep and rat oocyte stimulation of thymidine uptake by GC was inhibited with the GDF9 antibody (P < 0.05) but not control, irrespective of species of GC. Sheep oocyte stimulation of rat GC was also inhibited using an antibody to BMP15 (P < 0.05). However, when using the BMP15 antibody to block the effects of rat oocytes on rat GC, the inhibition of thymidine uptake was modest (i.e. ~10%) albeit significant (P < 0.05). The molecular forms of GDF9 and BMP15 in spent media were examined by Western blotting under reducing conditions. For both species, oocyte-secreted GDF9 was present in the mature form. For sheep oocytes, secreted BMP15 was present as promature and monomeric mature forms whereas from rats, trace amounts of mature form was sometimes, but not always, detected. Thus, in sheep both BMP15 and GDF9 are essential for regulating GC proliferation whereas in rats, although responsive to BMP15, GC proliferation is likely regulated primarily by GDF9.
