Ca2+- and Mg2+-activated ATP hydrolysis in normal and carious human dentine.

Ca2+- and Mg2+-activated ATP hydrolysis was measured in various layers of hard and soft carious dentine of freeze-dried teeth. Developing, intact, fully-formed, carious and gangrenous teeth were studied. Ten milligramme samples of dentine were analysed for enzyme activity by applying a bioluminescence method for measurement of ATP. The highest ATP-hydrolysis in hard dentine was observed in the coronal circumpulpal areas of developing teeth (14.2 mumol/min X mg protein X 10(-5]. In fully-formed teeth, the corresponding values were lower (6.62 mumol/min X mg protein X 10(-5]. Ca2+-activated ATP hydrolysis gave higher values than Mg2+-activated ATP hydrolysis. In coronal circumpulpal areas, enzyme activity was higher than in apical circumpulpal areas. The highest rate of hydrolysis in soft carious dentine was 4.96 mumol/min X mg protein X 10(-5).