EFFECT OF CULTURE CONDITIONS ON ARTIFICIAL ACTIVATION OF PORCINE OOCYTES MATURED IN-VITRO

The effects of culture media used and culture period for in vitro matu ration of porcine oocytes on their subsequent response to chemical and electrical activation, were investigated. Activated oocytes were iden tified by the presence of a pronucleus(ei) or cleavage. Porcine oocyte s were cultured for 24, 30, 36, 42 and 48 h in TCM199 with Earle's sal ts (199) supplemented with 10% fetal calf serum (199-FCS) before elect rical stimulation. Although few oocytes were activated after 24 h and 30 h of culture (54% and 6.1% respectively), the percentage of activat ed oocytes increased significantly to 93.2% after 42 h in culture (P < 0.05); however, when the culture period was extended to 48 h, there w as a significant decrease to 56.7% (P<0.05). Oocytes were also culture d in four types of media: (1) 199-FCS; (2) 199 supplemented with 5 mg mL(-1) bovine serum albumin (199-BSA); (3) Kreb's-Ringer bicarbonate s olution supplemented with 10% FCS (KRB-FCS); and (4) KRB supplemented with BSA (KRB-BSA). After 42 h of culture in each medium, the oocytes were electrically activated. Although rates of maturation of oocytes c ultured in the four media were similar (74.0-80.8%), all oocytes excep t those cultured in 199-FCS failed to be activated. In addition, oocyt es were cultured for 36, 42 and 48 h in 199-FCS and then stimulated by treatment with ethanol. Significantly fewer oocytes were activated in the chemically-treated group than in the electrically-treated group. These results indicate that culture conditions used for the culture of porcine oocytes in vitro are important with respect to their subseque nt response to artificial activation.