ABSTRACT
This chapter explores the relationship between membrane lipids and their permeability to Ca2+. Lipid-protein interactions are central to processes controlling the Ca2+ permeability of membranes. In postulating a role for nonbilayer phases in membrane permeability it would seem essential that they be transient in nature to preserve the normal impermeability of membranes to cations. The identification of a Ca2+ channel in the plasma membrane of many cells classified as nonexcitable has proved to be difficult because of the presence of the Ca2+ extrusion pump. The role of vitamin D in stimulating Ca2+ absorption in intestinal mucosal cells (enterocytes) is well recognized. It is possible that calcitriol influences the Ca2+ channel in a wide variety of cells, through altering the membrane lipid composition. Skeletal muscle cells and kidney cells are two such examples. A change in membrane lipid composition in response to calcitriol has been linked to modifications of the Ca2+ channel in intestinal brush-border membranes.
