Microphotometric quantitation of succinic dehydrogenase in whole isolated osteoclasts

The microphotometric quantitation of succinic dehydrogenase (SDH) in whole isolated osteoclasts was performed. Osteoclasts were obtained from imprints of the external metaphyseal area of tibia, a zone of physiological bone resorption. SDH was demonstrated histochemically and the reaction product was measured in a Zeiss Cytoscan microphotometer in arbitrary units (AU) of activity from 0 to 500. Total enzyme activity (TEA) was 10 to 50 AU in 78% of the cells. The enzyme concentration (MEC), taken as the activity per unit volume was 0.10 to 0.40 AU in 94% of the cells. Values of reactive cytoplasm area (RCA) were high for most of the cells, but lower for a few, probably mononuclear, osteoclasts. The correlation index for TEA vs RCA was significant. The study of enzyme activity in whole osteoclasts by microphotometric quantitation has been proven possible. This technique could be employed in further studies of enzyme activity of osteoclasts in other physiological or pathological states of bone resorption.