Comparative Biochemical Study of Otosclerosis and Osteogenesis Imperfecta

Abstract

The concentration of protein and the activities of lactate dehydrogenase (LDH), phosphofructokinase (PFK), and phosphohydrolase are abnormally elevated in bone affected by osteogenesis imperfecta. In otosclerotic bone, only phosphohydrolase activity is abnormally high, while LDH activity is abnormally low. The PFK from otosclerotic bone is insensitive to negative feedback regulation by citrate. The PFK from bone affected by osteogenesis imperfecta responds normally to citrate control. Selective inhibition of LDH activity by oxalate indicates an increase in the heart-type isozyme in otosclerosis and the muscletype isozyme in osteogenesis imperfecta. The biochemical data in this study indicate that the two diseases are enzymatically distinguishable. Therefore, it is unlikely that otosclerosis and osteogenesis imperfecta are determined by a common abnormal gene, as has been hypothesized elsewhere.