Biochemical Studies Of Otosclerosis: Protein and Enzymes in Stapedes and Cortical Bone

Abstract

Significant differences in the amounts of extracted protein and in lac-tate dehydrogenasc activity were found between normal cortical bone obtained from the inner end of the posterior metal wall and cortical bone from the same area in otosclerotic patients. The amount of protein extracted was 32% lower in cortical bone from otosclerotic patients. The activity of lactate dehydrogenase was 51 % lower on a per milliliter extract basis and 2(5% lower on a per microgram protein basis in cortical bone obtained from otosclerotic patients as compared to normal cortical bone. Since cortical bone is rarely affected by otosclerosis, these results could support the hypothesis, previously suggested, that the disease is a manifestation of a generalized metabolic disorder characterized by biochemical changes in the supporting tissues.

Differences were also found in the biochemical composition of stapedes from non-otosclerotic individuals as compared to stapedes from otoscìerotic patients. The activity of lactate dehydrogenase was lower in otosclerotic stapedes on both a per milliliter extract basis (percentage decrease, 38%) and a per microgram protein basis (percentage decrease, 49%). The activity of malate dehydrogenase was also lower in otosclerotic stapedes though not to the same degree as lactate dehydrogenase. An eightfold increase in alkaline phosphatase activity was found in otosclerotic stapedes as compared with normal.

These results suggest that otosclerosis is characterized by abnormal levels of enzyme activity, notably by decreases in lactate and malate dehydrogenase activities and by an increase in alkaline phosphatase activity.