Abstract
A colorimetric assay of free serum hydroxyproline, based on the method of Stegemann, has been conducted by adding improvements. The most important improvement was to use freeze-dried sulfosalicylic acid as deproteinizing reagent. This modified method was evaluated in regard to the accuracy of determination, the simplicity of procedure, and the applicability for routine work. A normal level of free serum hydroxyproline was obtained from 530 healthy Thoroughbred horses. It decreased significantly with the advance in age and was assumed to be related with bone development. Further, the level of free hydroxyproline was found high in many cases assumed to be of metabolic disorders of bone, including osteogenesis imperfecta, osteoporosis of the sesamoid, and hypoplasia. It was also high in some cases of such bone diseases as wobbles, periostitis, and bone metastasis of tumor. On the other hand, it was low in some cases of serious disorders of skeletal and cardiac muscles. From the findings of these clinical cases, it was concluded that serum hydroxyproline was a more reliable index for the diagnosis of bone diseases, particularly osteogenesis imperfecta, than serum alkaline phosphatase, calcium or phosphorus.
