Liquid chromatographic determination of hydroxyproline in tissue samples

We describe a reversed-phase assay of hydroxyproline in rat lung tissue using sarcosine for the internal standard and pre-injection reaction with both o-phthalaldehyde (OPA) and 9-fluorenylmethylchloroformate (FMOC). Intra-assay variability in the concentration range of 25–500 μM hydroxyproline was less than 1%. Normal rat (left) lung was found to have a hydroxyproline content of 1.08±0.18 mg/lung. This ability to measure minute amounts of hydroxyproline is being applied to the measure of collagen and pathological fibrosis.