CHOLESTEROL IN THE DISTAL PORTIONS OF DIFFERENTIATING AND FULLY DIFFERENTIATED RAT ODONTOBLASTS OBSERVED BY FREEZE-FRACTURE

Freeze-fracture replicas of rat molar tooth germs in conjunction with the 3-beta-hydroxysterol marker filipin were used to study the distrib ution of cholesterol in the distal portions of odontoblast plasma memb rane. Filipin-sterol deformations (interactions) appeared as clusters interspersed with deformation-free regions on the distal plasma membra ne of early differentiating odontoblasts. In fully differentiated odon toblasts, the whole distal membrane, including the process, was occupi ed by packed deformations with no free regions. It seems that early de veloping odontoblasts are poorer in cholesterol than the fully differe ntiated cells. As the content and/or distribution of 3-beta-hydroxyste rols (cholesterol) is known to influence membrane fluidity, the low ch olesterol content of early differentiating odontoblasts might be relat ed to the fluidity required for the budding off of matrix vesicles.