Interaction of sex hormones and cholesterol with monolayers of dipalmitoylphosphatidylcholine in different phase state.
Interactions of estradiol, progesterone, testosterone and cholesterol with dipalmitoylphosphatidylcholine (DPPC) monolayers at the air/water interface using Wilhelmy-Tensiometer were studied by measuring the change of the monolayer surface tension gamma (mN/m). In order to estimate the role of DPPC phase state on the deltagamma effects the experiments were carried out at three temperatures: 37 degrees C, 41.5 degrees C and 47 degrees C, since at 37 degrees C and 47 degrees C the formation of ripple gel Pbeta and liquid-crystalline Lalpha DPPC phases respectively were realized. Surface tension lowering capacity of the individual components at the air/water interface decreases in the order cholesterol>estradiol>progesterone>testosterone. The surface tension decrease of previously formed DPPC monolayer after addition of cholesterol and hormones follows the order cholesterol>>estradiol>progesterone approximately = testosterone. The higher activity of cholesterol and estradiol is interpreted by the existence of hydroxyl group in the steroid A-ring and hydrocarbon chain in the cholesterol structure and the same hydroxyl group in the estradiol, with possible formation of hydrogen bond between this group and the C=O group of the DPPC. It is shown that the existence of C-H chain in the molecular structure is stronger determinant than the OH group regarding the interactions with the DPPC monolayers. The very low capacity of progesterone and testosterone to interact with the DPPC monolayer is explained by the lack of the C-H chain and OH group in their structures. It was shown that the interaction forces of the steroids studied with DPPC monolayers were dependent on the DPPC phase state, being in any conditions stronger in the Lalpha (47 degrees C) than in Pbeta (37 degrees C) phase. At 41.5 degrees C more complex behavior of the components at the monolayers was observed. The obtained results could serve the concept of regulated entry of the steroid sex hormones into the cells with the participation of the lipid membrane components.
Dimitrov
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Department of Human and Animal Physiology, Sofia University St. Kliment Ohridski, Faculty of Biology, Bulgaria.
Lalchev
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ZI
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism*; D012739:Gonadal Steroid Hormones / Q000378:metabolism*; D006860:Hydrogen Bonding; D008563:Membrane Lipids / Q000502:physiology; D013256:Steroids / Q000737:chemistry; D013499:Surface Properties; D013500:Surface Tension / Q000187:drug effects; D013696:Temperature; D013997:Time Factors
D012739:Gonadal Steroid Hormones; D008563:Membrane Lipids; D013256:Steroids; D015060:1,2-Dipalmitoylphosphatidylcholine; D002784:Cholesterol