Rapid responses to estrogens

Besides the well known activity of transcription modulators, estrogens (ES) have been recently demonstrated to exert also rapid effects in several cell types, acting on intracellular second messengers and not involving gene transcription. The present reviews summarizes our knowledge on these different signalling pathways involved in ES action, focusing in particular on the most recent findings on classic and novel estrogen receptors (ERs) and their subcellular localization. The rapid effects exerted by ES and the characterization of their different receptors in human spermatozoa will be discussed using such cells as a good model of nongenomic ER system.