Maturation of rabbit follicular oocytes in a defined medium of varied osmolality

Rabbit oocytes from follicles greater than or equal to 1 mm in diameter were cultured for 18 h in a defined medium with osmolality adjusted in 20 mosmol increments from 230 to 350 mosmol by altering only the NaCl concentration. Adjustment, based upon determination of the osmolality of the medium, was necessary because a difference existed between calculated and achieved osmolality in this complex solution. The proportions of oocytes which matured to meiosis II with polar body formation were 64, 68, 64 and 65% in media of 250, 270, 290 and 310 mosmol, respectively.