Quantitative microchemical estimations of multiple additional enzyme systems (hexokinase, inorganic pyrophosphatase, isocitric dehydrogenase, aldolase, phosphoglucoisomerase, and acid phosphatase) as well as repeat evaluation of alkaline phosphatase, glucose-6-phosphate, and lactic and malic dehydrogenase have been made in the individual structural areas of the epiphyseal plate of the developing rabbit epiphysis. These observations are related to quantitative estimation of glucose, lactate, adenosine triphosphate, phosphate, and hydroxyproline content in these areas.
Large amounts of carbohydrate oxidative enzymes as well as substantial substrate and phosphatase content in the hypertrophic area of the epiphyseal plate indicate that this area of the epiphysis is not constituted of dead and dying cellular elements. These data support other tissue-culture and electron microscopic studies, which indicate this area to make a viable important cellular contribution to the process of enchondral bone formation.