Kinetic Model of the Action of 17α-Ethynylestradiol on the Capacitation of Mouse Sperm, Monitored by HPLC-MS/MS

Tereza Bosakova,Natasa Sebkova,Antonin Tockstein,Katerina Komrskova,Radomir Cabala

doi:10.3390/catal10010124

Abstract

17α-Ethynylestradiol (EE2), a synthetic estrogen used in contraceptive pills, is resistant to hepatic degradation and is excreted in the urine. It is chemically stable and has a negative impact on the endocrine system. The aim of this work was to mathematically describe the possible interaction of EE2 (200, 20, and 2 μg/L) with sperm estrogen receptors during sperm maturation, which is called capacitation. The concentrations of the unbound EE2 remaining in capacitating medium during 180 min of sperm capacitation were determined at 30 min intervals by high performance liquid chromatography with tandem mass spectrometric detection (HPLC-MS/MS) and the data obtained (relative concentrations Bt) were subjected to kinetic analysis. The suggested kinetic schema was described by the system of differential equations with the optimization of rate constants used to calculate the theoretical Bt values. Optimal parameters (overall rate constants K1–K5 and molar ratio n) were determined by searching the minimum of absolute values of the difference between theoretical and experimental Bt values. These values were used for the design of the theoretical B(t) curves which fit to experimental points. The proposed kinetic model assumes the formation of an unstable adduct between EE2 and the receptor in cytoplasm, which acts as an autocatalytic agent and gradually decomposes.

Highlights

The estrogenic hormone 17α-ethynylestradiol (EE2) belongs to a group of pollutants termed estrogenic endocrine-disrupting chemicals (E-EDC), which are chemical substances in the environment that have a negative impact on the endocrine systems of animals and humans [1]
Experiments were conducted to clarify whether EE2 is bound to bovine serum albumin (BSA), and, if so, for how long
The EE2 concentration decreases especially in the first 30 min and remains practically constant up to 90 min, which means that after 30 min no EE2 binds to BSA

Summary

Introduction

The estrogenic hormone 17α-ethynylestradiol (EE2) belongs to a group of pollutants termed estrogenic endocrine-disrupting chemicals (E-EDC), which are chemical substances in the environment that have a negative impact on the endocrine systems of animals and humans [1]. E-EDCs enter the environment in the form of waste products as a result of elevated production and consumption of a number of drugs, e.g., hormonal contraceptives or supportive substances [2], and already constitute a toxicological reproductive risk at very low concentrations (ng/L). These substances can, simulate the behavior of endogenic estrogenic hormones, which control a number of physiological processes, including sperm maturation and preparation for fertilization, binding to their receptors [2,3,4] (estrogen receptors (ERs), nuclear receptors (nER), and membrane (mER) and cytoplasmic (cER) receptors) [5,6]. The sperm could be morphologically mature, but not capable of fertilizing an egg [12]

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