Effect of Progesterone, Its Hydroxylated and Methylated Derivatives, and Dydrogesterone on Lipid Bilayer Membranes.

The interaction of progesterone (PG), 17-hydroxyprogesterone (17-OHPG), 21-hydroxyprogesterone (21-OHPG), medroxyprogesterone (MP), medroxyprogesterone acetate (MPA), and dydrogesterone (DYG), with zwitterionic dipalmitoyl phosphatidylcholine (DPPC) multilamellar liposome, was investigated as a function of drug concentration using Fourier transform infrared spectroscopy and differential scanning calorimetry. The results reveal that progesterone and its derivatives changed the physical properties of the DPPC bilayers by decreasing the main phase-transition temperature (T m) and enthalpy (ΔH m), abolishing the pre-transition and disordering the membrane. From the thermodynamic parameters analysis, we concluded that PG, 21-OHPG, and MPA are localized inside the membrane. Whereas, the insertion of 17-OHPG in the lipid bilayers cannot be excluded in view of the significant decrease in the transition enthalpy at two molar ratios. MP and DYG are rather localized near the polar heads of phospholipids at the interface water-lipid bilayer. PG derivatives increase the membrane fluidity in the order: PG ≈ 21-OHPG ≈ MPA > 17-OHPG > MP ≈ DYG. The distinct effects produced by steroids are discussed in terms of hydrophobicity and chemical structure.