[A model for the study of mechanical properties of membranes during hormone binding]

Bilayer lipid membranes (BLM) were used to reconstitute the hormonal reception system for insulin and glucagon. The effect of the hormones on both BLM and BLM with incorporated rat liver plasma membrane fragments (BLM-PM) was studied by measuring the elastic parameter of membranes--the Young modulus of elasticity in the direction perpendicular to the membrane plane (E perpendicular)--using an electroconstriction method. The effect of insulin (in a concentration of 10(-10) mol.l-1) on BLM-PM resulted in a much greater (about threefold) decrease of E perpendicular) compared to that on BLM. The high content of cholesterol had a strong inhibitory effect on this interaction. The effect of the insulin antagonist glucagon on BLM-PM resulted in opposite changes of the relative value of E perpendicular compared to the effect of insulin. While the effect of insulin resulted in a relative decrease of E perpendicular by about 60%, glucagon in the same concentration induced a relative increase of E perpendicular by about 8%.