Supplementation of canine oocyte in vitro maturation medium with progesterone, somatotropin, and epidermal growth factor

Abstract

The aim of this project was to assess meiotic resumption of canine oocytes in vitro in response to medium supplemented with either progesterone (P₄), somatotropin (ST), and/or epidermal growth factor (EGF). A mono-phasic in vitro maturation (IVM) system was tested using IVM medium supplemented with a) 0.0, 2000, 4000, or 8000 ng/ml P₄ (Exp. 1) or b) 0.0, 20, 200, or 2000 ng/ml P₄ (Exp. 2). Overall meiotic resumption rates for Exp. 1 were 58.5, 48.3, 40.0, and 45.3%, and for Exp. 2 were 48.1, 46.9, 54.0, and 35.5%, respectively. Treatments 200 and 2000 ng/ml were different statistically in meiotic resumption in Exp. 2. Maturation rates to MII for Exp. 1 were 1.9, 8.6, 1.8, and 1.9%, and for Exp. 2 were 14.7, 8.4, 10.7, and 9.9%, respectively with no significant differences in either experiment. Responsiveness of oocytes obtained at all estrous cycle stages was investigated in Exp. 2. Results indicated oocytes collected from ovaries of diestrous bitches had higher MII rates. A bi-phasic IVM system was also tested using oocytes from ovaries of diestrous or proestrous bitches. This system involved 1mM dbcAMP for 20 hours, then transfer of oocytes into IVM medium without inhibitor, but in the presence of 0.0, 20, 200, or 2000 ng/ml P₄ for an additional 48 hours. Significant differences in maturation to MII indicated oocytes obtained from ovaries of diestrous bitches were optimal. The effectiveness of ST, EGF, or combination of ST and EGF was also tested. Exp.l tested human ST (hST) at 0.0, 500, 1000, or 2000 ng/ml. Rates of meiotic resumption were 70.3, 57.6, 59.2, and 64.7%, and rates to MlI were 2.7, 0.0, 0.0, and 0.0%, respectively. No significant differences were observed in meiotic resumption or maturation to MII. Exp. 2 tested porcine ST (pST) and EGF. Maturation rates for meiotic resumption for control (without ST or EGF), 5000 ng/ml pST, 50 ng/ml EGF, and combination of pST and EGF were 70.7, 71.4, 78.4, 77.2%, and rates to MII were 19.0, 10.7, 2.0, and 12.3%, respectively. Significant differences in MII rates indicated the combination of pST and EGF was least effective.