Quantitation of Lactate Dehydrogenase of Developing Molar Teeth of the Mouse

¹ School of Dentistry, and Department of Anatomy, School of Medicine, University of Michigan, Ann Arbor, Michigan

Homogenates of developing first molar teeth of 2- to 21-day-old mice were analyzed by a quantitative spectrophotometric technic and by acrylamide gel electrophoresis for lactate dehydrogenase activity. Tissue sections of these teeth were also prepared, and the enamel and dentin widths were measured. The protein content of the teeth was determined and the wet weights were recorded. The enamel and dentin widths, the wet weight, and the protein content all increased with increasing age of the tooth, expressing the stages of mouse molar development. Lactate dehydrogenase activity, measured in millimicromoles of NADH formed per minute per milligram of wet weight of tissue and in millimicromoles of NADH formed per minute per microgram of protein, decreased with increasing age of the tooth. Five lactate dehydrogenase isozymes from the teeth were demonstrated after acrylamide gel electrophoresis. With increasing age of the tooth, there was a decrease in the activity of all the isozymes. After 10 days, the two most fast-moving isozymes could not be demonstrated. The LDH isozymes were identical in electrophoretic mobility to the isozymes from mouse heart muscle, liver, kidney, skeletal muscle, and serum. At present, an exact role and mechanism of lactate dehydrogenase in the developing tooth cannot be defined.