Highly effective method of human oocyte activation

Fresh and aged unfertilised human oocytes were activated by electroporation and by exposure to isotonic solution of mannitol supplemented with low concentrations of calcium, magnesium and chloride. Over 95% of the fresh oocytes were activated, all showing formation of one pronucleus and extrusion of the second polar body. Oocytes activated 1 and 2 days post-collection showed activation rates of 66.6% and 64.1%, respectively; however, the proportion of one-pronucleate oocytes in these groups was significantly lower (61.6% and 23.5%, respectively). There was no difference in the activation efficiency between the two activation modes. Twelve activated oocytes from the freshly collected group cleaved when left in culture. It is concluded that, in the human, a brief exposure to isotonic solution of mannitol with low concentrations of calcium, magnesium and chloride is a very effective activation stimulus.