Analysis of hydroxyproline by high performance liquid chromatography and its application to collagen turnover studies in bone cultures.

We describe a high performance liquid chromatography (HPLC) technique for separating and quantitating hydroxyproline in calvarial cultures. Using a reverse-phase Nova-Pak C18 column and a 140 mM sodium acetate, 0.05% triethylamine (TEA), 6% acetonitrile solvent system, we obtained a complete separation of hydroxyproline. Recovery of added standards ranged from 89 to 103% and intraassay variability was less than 8%. [3H]hydroxyproline measurements were used to examine changes in collagen turnover in rat calvariae labeled with [3H]proline and "chased" in the presence of 10 mM unlabeled proline. The addition of parathyroid hormone (PTH) during a 24-48 hour "chase" period increased the release of acid-soluble [3H]hydroxyproline into the culture medium, indicating an increase of fully degraded collagen. This method offers a sensitive and reproducible technique for monitoring changes in bone matrix degradation and in studying agents that modify this process.