Swelling of the intervertebral disc in vitro.

Slices of the intervertebral disc swell rapidly in aqueous solutions. Following swelling, a large proportion of the proteoglycans leach out. These changes can introduce artifacts into in vitro experimental work. Swelling results from the large Gibbs-Donnan osmotic pressure of the proteoglycans which the collagen network of the disc is unable to oppose alone. Swelling can be prevented by applying pressure to disc slices either mechanically or with iso-osmotic solutions.