Roles Of Different Calcium Channels In Regulating Susceptibility To Activation Stimuli Of Rat And Mouse Oocytes

In mammals,ovulated oocytes are arrested at the metaphase stage of the second meiotic division until fertilization or given physical and chemical stimulation,the activation of mammalian oocytes at fertilization or at parthenogenetic activation is always associated with intracellular Ca²⁺oscillations.However,rat oocytes are special:on the one hand,unlike other anamals oocytes,rat oocytes undergo spontaneous activation soon after collection from the oviduct,but the spontaneous activation is abortive with oocytes being arrested in MIII instead of forming pronuclei;on the other hand,rat oocytes are more susceptive to activation stimuli than mouse oocytes,the cause of this phenomenon had not been studied.We studied the different roles of calcium sensing receptor and Na⁺/Ca²⁺exchanger in rat oocytes and mouse oocytes susceptibility to activation stimuli and calcium fluctuation,we also comparised the different function of L-type calcium channel,T-type calcium channel,Ryanodine receptor,through which we obtained the reason of rat oocytes high susceptibility to activation stimuli is that the cooperative interaction of calcium sensing receptor,L-type calcium channel,T-type calcium channel result in calcium concentration auto rising in rat oocytes.Our experiment results demonstrated that:?1?Rat oocytes cytoplasmic calcium concentration can increase spontaneously,while mouse oocytes cannot.?2?There was a significant reduction in spontaneous activation rate?70%:30%,P<0.05?and calcium concentration?0.8:0.6,P<0.05?of rat oocytes after injection of hCG 19 h with2.5?M NPS-2143;There was a significant reduction in activation rate?38%:3%,P<0.05?and calcium concentration?3.5:0.9,P<0.05?of mouse oocytes after injection of hCG 19 h with 2?M NPS-2143.?3?There was a significant increasion in activation rate?21%:36%,P<0.05?and calcium concentration?1.8:2.5,P<0.05?of mouse oocytes after injection of hCG 13 h with 0.5?M Cinacalcet.?4?There was a significant increasion in expression of dimeric form calcium sensing receptor in rat oocytes and mouse oocytes after injection of hCG 19 h and 25 h than that of oocytes after injection of hCG 13 h?P<0.05?.?5?There was a significant reduction in spontaneous activation rate?77%:7.5%,P<0.05?of rat oocytes after injection of hCG 19 h with 50 mM NaCl;There was a significant reduction in activation rate?46%:26%,P<0.05?of mouse oocytes after injection of hCG 19 h with 75 m M NaCl.?6?There was a significant reduction in spontaneous activation rate?78%:13%,P<0.05?of rat oocytes after injection of hCG 19 h when inhibit L-type calcium channel,T-type calcium channel and calcium-sensing receptor.