Effects of gonadotrophins, growth hormone and prolactin on developmental competence of domestic cat oocytes matured in vitro

Abstract

Specific aims were to (1) examine the developmental capacity of felid oocytes matured in vitro and (2) determine the effects of gonadotrophins, growth hormone and prolactin on nuclear and cytoplasmic maturation oocytes in vitro. Oocytes were obtained from excised ovaries of 21 cats, and were matured for 45-46 h in modified CMRL-1066 culture medium (1 mM glutamine, 1 mM pyruvate and 20% bovine calf serum), with one of the following: (1) gonadotrophins (1.0 micrograms mL-1 hFSH+10 micrograms mL-1 hLH), (2) gonadotrophins+10 micrograms mL-1 growth hormone, (3) gonadotrophins+10 micrograms mL-1 prolactin, or (4) no hormones. Oocytes were inseminated with ejaculated cat sperm capacitated in TALP medium. Embryos were cultured in modified CMRL-1066 medium until developmental arrest, then stained with Hoechst 33342 to assess nuclear status or cell number. Gonadotrophins enhanced (P < or = 0.05) the incidence of nuclear maturation, but neither gonadotrophins, growth hormone nor prolactin improved fertilization or developmental potential of oocytes matured in vitro. Mean percentages of mature oocytes that were fertilized and cleaved to or beyond the 2, 4, 8 and 16-cell stages were 80, 77, 66, 42 and 24%, respectively. Three embryos progressed to 40-60 cells, but none developed a blastocoel. Thus, although gonadotrophins enhance nuclear maturation of oocytes in vitro, and mature oocytes are capable of fertilization and development to the morula stage, culture with growth hormone, prolactin or gonadotrophins during maturation in vitro does not enhance developmental competence or overcome the morula-to-blastocyst-stage block in development of domestic-cat oocytes matured in vitro.