Purinergic Signalling in Development

Abstract

Most early studies of the roles of nucleotides in development have been discussed in terms of their intracellular roles and as a source of energy. However, since it is now generally accepted that purines and pyrimidines have potent extracellular actions mediated by the activation of specific membrane receptors (see Burnstock 1997), many of these previous studies can now be reinterpreted. ATP and adenosine play key roles from the very beginnings of life, i.e. the moment of conception. ATP is obligatory for sperm movement (Yeung 1986) and is a trigger for capacitation, the acrosome reaction necessary to fertilise the egg (Foresta et al. 1992). Extracellular ATP also promotes a rapid increase in Na⁺ permeability of the fertilised egg membrane through the activation of a specific ATP receptor (Kupitz and Atlas 1993). Mg²⁺-ATPase activity has been localised on the entire surface of unfertilised eggs and in pre- and post-implantation embryos (Smith et al. 1983; Ishikawa and Seguchi 1985). Together with the demonstration that ATP-activated spermatozoa show very high success rates in fertilisation tests (Foresta et al. 1992), this strongly suggests that ATP is a key sperm-to-egg signal in the process of fertilisation.