17β-estradiol (estradiol) is a natural estrogen regulating reproduction including sperm and egg development, sperm maturation-called capacitation-and sperm⁻egg communication. High doses can increase germ cell apoptosis and decrease sperm count. Our aim was to answer the biological relevance of estradiol in sperm capacitation and its effect on motility and acrosome reaction to quantify its interaction with estrogen receptors and propose a model of estradiol action during capacitation using kinetic analysis. Estradiol increased protein tyrosine phosphorylation, elevated rate of spontaneous acrosome reaction, and altered motility parameters measured Hamilton-Thorne Computer Assisted Semen Analyzer (CASA) in capacitating sperm. To monitor time and concentration dependent binding dynamics of extracellular estradiol, high-performance liquid chromatography with tandem mass spectrometry was used to measure sperm response and data was subjected to kinetic analysis. The kinetic model of estradiol action during sperm maturation shows that estradiol adsorption onto a plasma membrane surface is controlled by Langmuir isotherm. After, when estradiol passes into the cytoplasm, it forms an unstable adduct with cytoplasmic receptors, which display a signalling autocatalytic pattern. This autocatalytic reaction suggests crosstalk between receptor and non-receptor pathways utilized by sperm prior to fertilization.

• Keywords
• 17β-estradiol, CASA, HPLC MS/MS, acrosome reaction, autocatalysis, capacitation, kinetics, sperm,
• MeSH
• Acrosome Reaction drug effects   MeSH
• Estradiol metabolism   pharmacology   MeSH
• Sperm Capacitation drug effects   physiology   MeSH
• Kinetics MeSH
• Sperm Motility drug effects   MeSH
• Mice, Inbred C57BL MeSH
• Progesterone pharmacology   MeSH
• Signal Transduction * MeSH
• Semen drug effects   metabolism   MeSH
• Chromatography, High Pressure Liquid MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Estradiol MeSH
• Progesterone MeSH

Fluorides and fluoroaluminates decrease mouse sperm fertilizing potential by modifying the process of sperm preparation for fertilization, so-called capacitation, followed by acrosome reaction (AR). Capacitation was monitored by protein tyrosine phosphorylation (pTyr), and AR was induced consequently. The aim of this study was to apply kinetic analysis to the previously obtained dependences of pTyr and AR at capacitation times, and propose a mathematical theory for a mechanism when sperm maturation ability is amended by external stimuli. The experimental input data, previously obtained, are consistent with the proposed theory and the results of kinetic analysis show that sperm capacitation runs as two subsequent first-order steps. Firstly, an unstable intermediate is formed and then gradually decomposes. The time corresponding to the maximal production of the unstable intermediate is probably most suitable for sperm obtaining the ability to fertilize the egg. The presented calculations indicate that the application of kinetic analysis can serve as a tool to predict or confirm a course of biological events that are modified by external factors, and therefore the proposed theory shall be of interest to a broad scientific audience.

• Keywords
• Acrosome reaction, Capacitation, Fluoride complexes, Kinetics, Sperm fertilizing ability, Tyrosine phosphorylation,
• MeSH
• Acrosome Reaction * MeSH
• Fluorine adverse effects   pharmacology   MeSH
• Fluorides adverse effects   pharmacology   MeSH
• Aluminum adverse effects   pharmacology   MeSH
• Mice, Inbred BALB C MeSH
• Mice MeSH
• Spermatozoa cytology   drug effects   physiology   MeSH
• Sperm Maturation MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Fluorine MeSH
• Fluorides MeSH
• fluoroaluminum MeSH Browser
• Aluminum MeSH