A Study of the Interaction between Progesterone and Membrane Lipids*

Abstract

The ability of progesterone to associate with phospholipid was examined in a model membrane system. Molecular interaction was assessed by measuring the enthalpy of the phase transition of dipalmitoylphosphatidylcholine liposomes by differential scanning calorimetry. The response was compared to cholesterol, a constituent of cellular membranes. Unlike cholesterol, progesterone caused minimal disruption of the phospholipid bilayer phase properties at concentrations ranging from 5-33 M %. However, it interacted with the phosholipid to a greater degree when cholesterol was included in the liposomes. Progesterone can intercalate into phospholipid bilayers containing cholesterol, and raise the prospect that there may be some diffusion of the hormone across the plasma membrane.