A Critique on the Relevance of Membrane Potentials to the Mechanism of Nidation

It has been proposed that contact between the rat blastocyst and the endometrium is conditioned by like electrical charges on their membranes. Clemetson, Mallikarjuneswara, Moshfeghi, Carr & Wilds (1970) and Clemetson, Kim, Mallikarjuneswara & Wilds (1972) presented data purporting to show that treatment of rats with oestrogen or with progesterone could modify the potential of the endometrium and influence contact. Clemetson et al. (1970) stated that 'the high negative membrane potential under the influence of progesterone may be the cause of delayed implantation by repelling the negatively charged blastocyst. Conversely, the lowering of the negative membrane potential under oestrogen treatment could remove or reduce this repelling action and favour contact necessary for attachment and subsequent implantation.' The mechanism by which these changes in potential occurred was attributed to hormonally controlled alterations in the concentrations of sodium and potassium ions in the luminal and intracellular fluids of the endometrial cells. Clemetson