Comparisons of processing with and without potassium pyroantimonate in quantitative autoradiography of calcium in developing teeth of the frog Rana pipiens

To assess the effect of potassium pyroantimonate (PPA) on the retention and localization of 45Ca in developing teeth, six frogs were injected with 45CaCl 2, and pairs decapitated after 5 min, 1 h and 24 h; blocks of developing teeth were dissected and processed with and without PPA. Sections from 36 teeth in similar stages of development were selected from the PPA-processed blocks and similar sections from 36 teeth without PPA treatment served as controls; all were similarly processed for autoradiographic examination. Each tooth was drawn to scale; the areas of enamel, dentine and predentine were measured and the net number of silver grains in each tissue determined after subtraction of background counts. Counts in the PPA specimens were consistently higher for all tissues and all time intervals and the differences between experimental and control mean counts were statistically significant. No differences in the distribution pattern of 45Ca were seen in any of the three tissues. The unaltered distribution but increased concentration of 45Ca with PPA suggest the formation of PPA complexes with loosely-bound calcium, which will enhance its retention during processing for autoradiography.