Natural and synthetic compounds called endocrine-disrupting chemicals can interfere with normal hormone binding to convey inaccurate signals or send mixed messages that may result in altered health outcomes of both wildlife and humans. Estriol is one of natural origin endocrine disruptors and it is metabolite of 17β-estradiol. The aim of this work was to develop a method for determining free estriol available to capaciting sperm. In order to determine a status of estriol during mouse sperm capacitation in vitro a high performance liquid chromatography HPLC method with UV detection was used. A free estriol, and the estriol bound to the bovine serum albumin in capacitation medium can be quantified by the proposed method. A reversed-phase separation mode using a SunFire C18 column with a simple mobile phase composed of acetonitrile and water, methanol and water at the ratio 40/60 (v/v) was applied. Our results show that the level of free estriol available for mouse spermatozoa during capacitation in vitro can be quantified by HPLC method with UV detection. Therefore, this method represents an important tool to determine the amount of environmental estrogens, such as estriol, bound to sperm cells at the specific time point of capacitation in vitro.
In humans, CD46 has been detected on the acrosomal membrane in sperm, in contrast to widespread surface expression on somatic cells where it plays a key role in the protection from complement attack. In rodents, CD46 is expressed solely on the acrosomal membrane of mature sperm and their immediate precursors, spermatids. A monoclonal antibody against the short consensus repeat (SCR1) ectodomain of CD46 blocks binding of human sperm to zona-free oocytes in vitro. However, CD46-knockout mice are fertile and have an accelerated spontaneous acrosome reaction. Wild-caught field mice (Apodemus) also exhibit a rapid acrosome reaction and CD46 is not expressed in Apodemus sperm. CD46 may, therefore, play a role in stabilization of the acrosomal membrane. Two other complement regulatory proteins, CD55 and CD59, are localized on the plasma membrane of mammalian sperm. In human sperm, CD55 and CD59 are expressed also on the inner acrosomal membrane. It remains to be clarified what is the role of CD46, CD55 and CD59 during fertilization and what are the advantages of not expressing CD46 in field mice sperm.