Changes in testosterone or temperature during the in vitro oocyte culture do not alter the sex ratio of bovine embryos.
High follicular testosterone levels have been associated with a skew in the sex ratio in favor of males following in vitro fertilization, whereas egg incubation temperature has been found to influence sex ratio in some reptiles. The incubation temperature interferes with the aromatase activity, resulting in a sex determination mechanism thought to be lost in mammals. In this work we aimed to test the effects of testosterone on sex ratio of bovine embryos produced in vitro and to determine whether effects of sex and temperature are effectively decoupled in mammals. Bovine oocytes were in vitro matured for 22 hr in TCM199, PVA, FSH and LH after a 22 hr meiotic arrest in TCM199, PVA and roscovitine 25 microM. Matured oocytes were in vitro fertilized and cultured up to Day 3, and embryos having three or more cells were sexed. In the first experiment, testosterone (0, 30, 300 and 1,500 nM), present both during meiotic inhibition and subsequent in vitro maturation (IVM), did not affect development rates or embryonic sex ratio. In the second experiment, increasing incubation temperatures (38, 39 or 40 degrees C) during meiotic inhibition and subsequent IVM, reduced embryo development, but did not change the sex ratio. Under our experimental conditions, testosterone does not promote a preferential selection of Y-chromosome bearing spermatozoa by the oocyte, and temperature and sex ratio seems to be decoupled in mammals.
Díez
Carmen
C
SERIDA, Area de Genética y Reproducción Animal, Gijón, Spain. mcdiez@serida.org
Bermejo-Alvarez
Pablo
P
Trigal
Beatriz
B
Caamaño
José Néstor
JN
Muñoz
Marta
M
Molina
Irene
I
Gutiérrez-Adán
Alfonso
A
Carrocera
Susana
S
Martín
David
D
Gómez
Enrique
E
D000818:Animals; D002417:Cattle / Q000502:physiology*; D046508:Culture Techniques; D047108:Embryonic Development / Q000187:drug effects / Q000502:physiology; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods / Q000662:veterinary*; D050173:Genes, Y-Linked / Q000502:physiology; D006358:Hot Temperature / Q000009:adverse effects*; D008297:Male; D009865:Oocytes / Q000187:drug effects* / Q000254:growth & development; D012732:Sex Determination Analysis / Q000662:veterinary; D012744:Sex Ratio; D013094:Spermatozoa / Q000502:physiology; D013739:Testosterone / Q000494:pharmacology*
D013739:Testosterone