The oocyte undergoes various events during maturation and requires many substances for the maturation process. Various intracellular organelles are also involved in maturation of the oocyte. During the process glucose is essential for nuclear and cytoplasmic maturation, and adenosine triphosphate is needed for reorganization of the organelles and cytoskeleton. If mitochondrial function is lost, several developmental defects in meiotic chromosome segregation and maturation cause fertilization failure. The endoplasmic reticulum, a store for Ca2+, releases Ca2+ into the cytoplasm in response to various cellular signaling molecules. This event stimulates secretion of hormones, growth factors and antioxidants in oocyte during maturation. Also, oocyte nuclear maturation is stimulated by growth factors such as epidermal growth factor. This review summarizes roles of organelles with focus on the Golgi apparatus during maturation in oocyte.

The objective of this study was to investigate the efficiency of nicotinic acid on sperm cryosurvival and fertilization ability in frozen-thawed boar semen. Boar semen was collected by glove-hand method and was frozen using freezing solution treated to 0, 5, 10 and 20 mM of nicotinic acid. The frozen sperm for sperm characteristic analysis was thawed such as viability, acrosome reaction, and mitochondrial integrity. The frozen-thawed sperm was estimated by SYBR14/PI double staining for viability, FITC-PNA/PI double staining for acrosome reaction and Rhodamine123/PI double staining for mitochondrial integrity using a flow cytometry. The embryo was estimated in vitro development and DCFDA staining for reactive oxygen species assessment. As results, frozen-thawed sperm viability was significantly higher in 5 and 10 mM (61.1 ± 1.5%, 64.7 ± 2.0%) of nicotinic acid than other groups (0 mM, 52.1 ± 2.3%; 20 mM, 47.8 ± 5.1%, P<0.05). The live sperm with acrosome reaction was significantly higher in 5 and 10 mM of nicotinic acid (26.1 ± 1.8%, 24.9 ± 1.5%) than other groups (0 mM, 35.3 ± 0.8%; 20 mM, 36.5 ± 1.9%, P<0.05). The live sperm with mitochondrial integrity was significantly higher in 5 and 10 mM (84.2 ± 3.6%, 88.4 ± 2.3%) of nicotinic acid than other groups (0 mM, 77.3 ± 4.4%; 20 mM, 73.3 ± 3.6%, P<0.05). Blastocyst rate of in vitro development was significantly higher in 10 mM (17.0 ± 1.3%) of nicotinic acid than other groups (0 mM, 9.4 ± 0.5%; 5mM, 12.6 ± 0.8%; 20 mM, 5.0 ± 1.0%, P<0.05). Moreover, total cell number was higher in 5 and 10 mM (53.6 ± 2.9%, 57.9 ± 2.8%) of nicotinic acid than other groups (0 mM, 41.0 ± 1.4%; 20 mM, 23.2 ± 2.8%, P<0.05). Hydrogen peroxide in embryos was lower in 5 mM nicotinic acid (0.7 ± 0.1%) than other groups (0 mM, 1.0 ± 0.1%; 10mM, 0.9 ± 0.0%; 20 mM, 1.4 ± 1.0%, P<0.05). In conclusion, nicotinic acid-treated semen improves cryosurvival and quality of spermatozoa. Also, the fertilized oocytes with nicotinic acid improve quality of embryo and blastocyst formation.

This study was conducted to investigate stimulatory effect of epidermal growth factor (EGF) on nuclear maturation and the expression level of EGF-receptor (EGFR), GM-130 (a marker of Golgi apparatus), transport protein Sec61 subunit beta (Sec61β), and coatomer protein complex subunit gamma 2 (COPG2) in porcine oocytes. The cumulus-oocyte complexes were collected from follicle with 3-6 mm in diameter. They were incubated in medium with/without EGF for 22 h (IVMⅠ) and subsequently incubated hormone-free medium with/without EGF for 22 h (IVMⅡ). Nuclear maturation state was checked by aceto-orcein stain. Protein expression of EGFR, GM-130, Sec61β, and COPG2 were measured by immunofluorescence. In results, nuclear maturation of oocytes in EGF non-treated oocytes were significantly lower than EGF-treated groups at IVMⅠ or IVMⅡ stage (P<0.05), whereas maturational rate in EGF treatment groups at both of IVM stage was higher in among the all treatment groups (P<0.05). EGFR, GM-130, Sec61β and COPG2 were expressed in the cytoplasm of oocytes. Especially, GM-130 and EGFR were strongly expressed, but Sec61β and COPG2 were weakly expressed in cortical area of cytoplasm. The protein level of GM-130, Sec61β, and COPG2 were significantly higher in the EGF-treated groups (P<0.05). However EGFR was no difference between non EGF-treated groups and control. In conclusion, EGF plays an important role in the systems for oocyte maturation with endoplasmic reticulum and Golgi apparatus. In addition, the protein levels of Sec61β and COPG2 could be changed by EGF in the porcine oocytes during maturation.