Effects of Hard Tissue-Related Hormones on the Intracellular Calcium Ion of the Rat Odontoblasts

Abstract

We examined the effects of PTH, calcitonin (CT) and parotin subunit on the intracellular Ca ²⁺ of odontoblasts using a chelate reagent, FURA2-AM. Rat CT (rCT), at a final concentration of 0.01μM, induced a gradual lowering of Ca²⁺, and addition of ATP, in the presence of CT, resulted in a partial and short-lasting recovery of Ca²⁺. At higher concentrations, it caused a rapid decrease of Ca²⁺. CTs of other animal species showed similar effects. Human PTH (hPTH) added at concentrations of 0.01, 0.1 and 1μM, caused no significant changes in intracellular Ca²⁺. Parotin subunit caused a rapid lowering of Ca²⁺ which was seen already at 0.01μM. rCT added after treatment with hPTH caused an immediate decrease of Ca²⁺ to zero level, showing that CT action was enhanced by pretreatment with hPTH. This enhancement was also confirmed by addition of hPTH after rCT, where at 1μM, it caused further acute decrease in Ca²⁺. After intracellular Ca ²⁺ was lowered by CT pretreatment, parotin, at 0.1μM, induced a further but gradual decrease of Ca²⁺. The present results, together with our previous study indicating that hPTH increased cAMP production and that CT inhibited the PTH action, made it clear that all the hormones affect odontoblasts, and that CT and parotin act via Ca-related signal transduction system, while PTH acts via CAMP-PKA-related cascade. Possible crosstalk of both systems was also suggested.