Effects of Alizarine Red S Injections on the Teeth and Bones of Macacus rhesus Monkey. ∗

Seventeen Macacus rhesus monkeys of mixed or adult dentition, ranging in age from 1½ to 7 years, 1 were given multiple intravenous, intraperitoneal or subcutaneousi injections of 5-10 cc. of 2% Alizarine Red S (Sodium Sulphalizarate) of color index 1034 (Coleman and Bell Company) at 5- to 30-day intervals. The time between the last injection and death ranged from 3 hours to 125 days. The dosage ranged from 40 to 60.5 mg. per kilo.

For each injection a distinct red ring was observed in the dentin and the bone that were forming and calcifying at the time. 2 This effect was immediate, as indicated in the animals sacrificed within a few hours after the last injection. In 6 animals 4 months elapsed between the first injection and death. This long survival did not alter the staining reaction.

Measurement of the distances between successive rings indicated the amount of apposition during the corresponding intervals. The rate of apposition of dentin based on 1164 measurements made chiefly in the ground sections of bicuspids and molars ranged from 1.6 to 5.6 μ per 24 hours. This range may be explained on the basis of a growth gradient with its maximum at the cusp and along the outer dentinal surface and its minimum apically and toward the pulp. Alizarine lines were also found in the cementum. Definite staining effects could be recognized macroscopically in the jaws and long bones.

Subcutaneous administrations were found to be complicated by a sloughing of the tissues at the site of injection. Intravenous injections gave sharper effects than intraperitoneal injections of the same dose. However, thrombosis of the veins at or near the site of injections occurred frequently. The intraperitoneal injections were as effective as the intravenous ones when the dosage was increased to 10 cc.