Density determinations of human parathyroid glands by density gradients

The densities of human parathyroid glands were measured in density gradient columns of various media. Percoll (an aqueous colloidal solution of polyvinylpyrrolidone-coated silica), equilibrated to 300 mOsm with sodium chloride, was found to be the ideal gradient medium for density measurements of tissues with a density greater than 1.0 g/ml. which includes most parathyroid glands. The densities of the glands varied between 0.96 and 1.06 g/ml. Density measurements in gradients of Percoll were simple and reproducible and were made with an accuracy of approximately 0.001 g/ml. In other gradient media (aqueous solutions of sucrose and Ficoll, and organic solvents) there was a drift in density caused by osmotic or lipid-solving effects of the media. For measurements of densities less than 1.0 g/ml no ideal gradient medium was found, but a silicon oil or carbon tetrachloride/kerosone gradient could be used with somewhat reduced accuracy. It is concluded that the density gradient technique with the use of Percoll is potentially useful as a complement to routine histopathological parathyroid diagnosis, as glandular density is a good indicator of the relative proportions of parenchymal and fat tissue.