Enzyme histochemical analysis of Meckel's cartilage.

Osteogenesis of the body of the mandible in embryonic and neonatal rats was studied histologically and by histochemistry to determine the role of Meckel's cartilage in bone formation. Meckel's cartilage showed intense activity of lactate dehydrogenase and NADH2-diaphorase and weak activity of acid phosphatase, indicating a functioning citric acid cycle, pentose phosphate shunt and a capacity for anaerobic metabolism. The activity of these enzymes declined after hypertrophy of Meckel's cartilage. Alkaline phosphatase was the major enzyme of mineralising mandibular osteoid and was present in the osteoblasts and osteoprogenitor cells but not in Meckel's cartilage. After the differentiation of Meckel's cartilage and intramembranous bone, Meckel's cartilage supported mandibular bone formation by endochondral ossification in the anterior part of the mandible.