THE THIOL REAGENT, THIMEROSAL INDUCES INTRACELLULAR CALCIUM OSCILLATIONS IN MATURE HUMAN OOCYTES

The aim of this study was to investigate the effects of thimerosal on intracellular calcium in human oocytes related to the stage of nuclear maturity. A total of 20 oocytes from superovulated women undergoing g amete intra-Fallopian transfer (GIFT) were studied. The calcium-sensit ive fluorescent dye Fura-2 was used to monitor intracellular calcium. Regular oscillations in the concentration of cytosolic calcium were ob served in 13 out of 20 oocytes following exposure to thimerosal; five oocytes did not respond to thimerosal treatment, and spontaneous oscil lations of cytosolic free calcium were recorded in two oocytes. Thimer osal induced oscillations of intracellular calcium in a significantly higher proportion of metaphase II oocytes (10/11) compared with metaph ase I oocytes (3/8; P < 0.2), These findings demonstrate that thimeros al is a potentially useful agent for the study of the calcium signalli ng processes in human eggs and suggest that the underlying cellular me chanisms develop at a relatively late stage of oocyte maturation.