EFFECT OF KN-62, A SELECTIVE INHIBITOR OF CALMODULIN-DEPENDENT KINASE-II, ON MOUSE OOCYTE ACTIVATION

Purpose: Our purpose was to determine the association of calmodulin-de pendent protein kinase II (CaMKII) with oocyte activation and to explo re the network of protein kinases during mammalian fertilization. Meth ods: Mouse M-II oocytes were collected after superovulation induced by PMSG-hCG injection. The oocytes were inseminated or artificially acti vated by Ca ionophore (A23187) or 12-O-tetradecanoyl phorbol 13-acetat e (TPA). The effects of KN-62, a specific and selective inhibitor of c almodulin-dependent protein kinase II, on second polar body emission ( 2PBE), pronuclear formation (PF), and cortical granule exocytosis (CGE ) during fertilization or after artificial oocyte activation were inve stigated. Results: KN-62 inhibited 2PBE and PF after sperm or Ca ionop hore inducing activation. Additionally, PF was inhibited by KN-62 afte r TPA activation, whereas KN-6 did not inhibit CGE in any case. KN-04, an inactive form of KN-62, did not inhibit significantly 2PBE, CGE, o r PF. When oocytes were exposed to KN-62 after Ca ionophore or TPA act ivation, no inhibitory effects on 2PBE or PF were observed. Conclusion s: The CaMKII activation that occurs after fertilization or artificial activation of mouse oocytes is presumably secondary to increases in t he intracellular free calcium. concentration. As determined by the use of inhibitor CaMKII activity is associated with 2PBE and PF but not w ith CGE.