CHANGES IN THE PHYSICAL CHARACTERISTICS OF THE HY- ALURONATE OF GROUND SUBSTANCE WITH ALTERA- TIONS IN SODIUM CHLORIDE

Hyaluronic acid was first isolated in 1934 by Meyer and Palmer (1) from the vitreous humor of the cattle eye. It has since been isolated from the ground substance of some connective tissues, synovial fluid, cartilage, cornea, umbilical cord, bacteria, and possibly identified in the ground substance of other material (2, 3). The sub-stance is a high polymer with a monomer of a disaccharide, f3-glucuronido-1-3 N-acetylglucosa-mine, constituting the repeating unit (4). Each of these monomers contains an ionizable carboxyl group. The compound is one of a large group of natural polyelectrolytes. The connective tissue, in the ground substance of which hyaluronic acid is found, is a ubiquitous material, and thought to be of importance in sup-port, ion transport, storage, and repair (3). Changes in the physical characteristics of hy-aluronic acid may be of importance in the exercise of these functions. Studies of the physical properties of hyaluronic acid by various methods have been reported (5-14). We have studied the relative changes in certain biophysical measurements of hyaluronate solutions including flow birefringence, viscosity, sedimentation and light scattering as a functio