Action of parathyroid hormone, with special reference to its anabolic effect on different kinds of tissues in rats (III).

The effect of parathyroid hormone (PTH) on mineralization and matrix formation was studied on the incisal dentin of immature rats by using a time marker as well as the histochemical method. 1. When the hypersecretion of PTH was caused by a low calcium diet, mineralization and matrix formation were both accelerated. 2. Both mineralization and matrix formation were clearly inhibited by parathyroidectomy or thyro-parathyroidectomy which brought about a widening of the predentin (dentinoid) as a result of the conspicuous inhibition of mineralized matrix formation. The maturation of the matrix seemed to be inhibited also. 3. Demineralization was lower and slower in the labial than in the lingual dentin. 4. The inhibitory effect disappeared totally by the PTH injection, but the restoration of matrix formation was faster compared with that of mineralization. 5. The increase or decrease in mineralization did not necessarily occur in parallel with that in matrix formation. 6. Acid mucopolysaccharide formation in the dentin depended clearly on the quantity of PTH.