Fig. 5.

Comparison of calcium secretion at pH 7.4 and 7.8. Secretion was assayed with Alizarin (red stained clusters) in media supplemented with 10 nM calcitriol and 10 mM β-glycerophosphate after 14 and 21 days. At pH 7.8, stained cells and huge calcium deposits were clearly visible on days 14 and 21, respectively. At pH 7.4, no calcium could be detected until day 21.