Fluctuations in surface pH of maturing rat incisor enamel are a result of cycles of H + -secretion by ameloblasts and variations in enamel buffer characteristics

article i nfo It is disputed if ameloblasts in the maturation zone of the enamel organ mainly buffer protons released by hy- droxyapatite (HA) crystal growth or if they periodically secrete protons to create alternating acidic and alkaline conditions. The latter hypothesis predicts alternating pH regimes in maturing enamel, which would be affected by pharmacological interference with ameloblast H + -secretion. This study tests these predictions. Colorimetric pH-indicators and ratiometric fluorometry were used to measure surface pH in maturation zone enamel of rat incisors. Alternating acidic (down to pH 6.24 ± 0.06) and alkaline zones (up to pH 7.34 ± 0.08) were found along the tooth coinciding with ameloblast morphological cycles. Underlying the cyclic pattern, a gradual decrease in pH towards the incisal edge was seen. Vinblastine or FR167356 (H + -ATPase-inhibitor) dis- turbed ameloblast acid-secretion, especially in the early parts of acidic zones.