| Summary: | 博士 === 中興大學 === 動物科學系所 === 95 === The objectives of this study were to determine the effect of a short-term heat shock (HS) on the developmental competence and cellular physiology including expression of heat shock protein 70 (hsp 70), apoptosis and alteration of intracellular calcium concentration ([Ca2+]i) of the in vitro matured (IVM) porcine oocytes. Cumulus-oocyte-complexes (COCs) were collected from local abattoirs and were IVM in NCSU-23 medium for 42 h. Matured oocytes were selected and randomly allocated to different treatment groups. The COCs were cultured at 39 ℃ for 0 or 4 h in the control groups (without HS) and at 41.5 ℃ for 1, 2, or 4 h in the HS groups. The expression of hsp70 was not significantly different among all groups. TUNEL-positive signals (apoptosis) was not observed in the heated oocytes compared to the Controls, but the intensity of Annexin V-FITC signals increased with the duration of HS and in vitro culture. The cleavage and blastocyst rates were declined after more than 2h HS. In addition, The Ca2+ releasing ability of matured oocytes was enhanced by a shorter duration (2h) of HS, but it declined after prolonged heat exposure and in vitro culture. After spindles/chromosomes were exchanged between non-HS oocytes and HS2h oocyets, different sensitivity of the nucleus and the ooplasma was not clearly observed. The physiologic effects and mechanisms of HS on oocytes are complex processes. HS causes multiple changes of the oocyte including enzymatic reactions, ionic influxes, DNA structure and cytoskeleton, etc. Changes in the [Ca2+] of oocytes in response to signaling molecules after different intensities of HS may be important to evaluate their developmental competence. The delicate equilibrium between the deleterious effects and thermotolerance of oocytes or embryos in response to HS is a decisive factor determining their developmental destiny. This study provides clues for further investigations to clarify the mechanism of thermal resistance in oocytes. Further investigations will be focused on regulation of Ca2+-related kinases and looking into their encoding genes responsible for regulation of thermotolerance.
|
|---|
