| Popis: |
In mammalian oocytes, the maintenance of meiotic prophase I arrest prior to the surge of luteinizing hormone (LH) that stimulates meiotic maturation depends on a high level of cAMP within the oocyte. In mouse and rat, the cAMP is generated in the oocyte, and this requires the activity of a constitutively active, Gs –linked receptor, GPR3 or GPR12, respectively. To examine if human oocyte meiotic arrest depends on a similar pathway, we looked at whether human oocytes express the same components for maintaining arrest as rodent oocytes using RT-PCR and Western blotting. RNA encoding GPR3, but not GPR12, was expressed. RNA encoding adenylate cyclase type 3 (AC3), which is the major adenylate cyclase required for maintaining meiotic arrest in the mouse oocyte, was also expressed, as was Galphas protein. To determine if this pathway is functional in the human oocyte, we examined the effect of injecting a function blocking antibody against Galphas on meiotic resumption. This antibody stimulated meiotic resumption of human oocytes that were maintained at the prophase I stage using a phosphodiesterase inhibitor. These results demonstrate that human oocytes maintain meiotic arrest prior to the LH surge using a similar signaling pathway as rodent oocytes. |
