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

Abstract

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 with⁴⁵Ca²⁺ 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 µm 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.