ATP-dependent uptake of Ca2+ by a microsomal fraction from rat incisor odontoblasts

Intracellular vesicles containing alkaline phosphatase and Ca2+-ATPase activity were isolated in the microsomal fraction from free-dissected odontoblasts of rat incisors. The microsomal fraction was incubated with 45Ca2+ to study Ca2+ uptake. ATP stimulated Ca2+ uptake, whereas little uptake occurred without ATP. The maximal effect was obtained with 3mM ATP. The ATP-dependent uptake was linear for 2 h. Increasing the pH up to pH 8.2 resulted in an increased uptake. Mg2+ was stimulatory with an optimal effect at a 6mM concentration. Increasing concentrations of Ca2+ up to 100 micrometer enhanced the uptake. A correlation between Ca2+ uptake and Ca2+-ATPase in intracellular vesicles as well as a possible function in the calcification process are discussed.