Comparative metabolic enzymatic activity in trabecular as against cortical osteoblasts.

On the basis of studies with bone-seeking isotopes, it is generally believed that the metabolic activity of osteoblasts of the trabecular bone is greater than that of the osteoblasts of the cortex. This implies that the oxidative activity, which provides the energy for biosyntheses, will also be greater in the former than in the latter. In the present study, direct measurement of the activities of representative enzymes of the major oxidative pathways, as well as of alkaline phosphatase, showed that the reverse pertained. However, owing to the greater cellularity of trabecular bone, the activity per unit mass of bone may be higher in the trabecular bone.