Thyroid Hormones Affect the Membrane Dipolar Organization: Is It a General Event in Their Non-genomic Action?

Abstract

The surface balance technique was employed to study the interactions of 3,5,3′,5′ tetraiodo L-thyronine, 3,5,3′ triiodo L-thyronine, and 3,5-diiodothyronine with monomolecular phospholipid monolayers spread at the air-water interface. With this technique the insertion of thyroid hormones into egg yolk phosphatidylcholine was investigated. An increase of surface pressure and a substantial decrement in surface potential were observed after the injection of these hormones beneath a phospholipid monolayer. The negative dipole contribution upon hormone interaction opposes the well-known positive contribution of phospholipids. These effects correlated with iodo content of the thyroid molecule analogues 3,5,3′,5′ tetraiodo L-thyronine >3,5,3′ triiodo L-thyronine >3,5-diiodothyronine. To our knowledge, these observations suggest a new and surprising effect of thyroid hormones on the regulation of transmembrane dipolar organization.