Variation in alkaline-phosphatase activity with changing load on the mandibular condylar cartilage in the rat.

Biomechanical loads were varied by feeding diets of different consistencies. One group was fed hard diet for eight weeks, a second soft diet for eight weeks, and a third soft diet for four weeks followed by four weeks of hard diet. In all groups, alkaline-phosphatase activity was localized primarily in cells and extracellular matrix of the hypertrophic zone, and in cells lining trabeculae of the subcondylar bone. The staining intensity in the hypertrophic zone was slightly less in the soft-diet and soft/hard-diet groups than in the hard-diet group. The thickness of the cell layer staining positively for alkaline-phosphatase was significantly less in the soft-diet group than in the hard- and soft/hard-diet groups.