Alterations in Long Bones of Young Albino Rats Induced by Dihydrotachysterol. (Hytakerol). ∗

Summary

Groups of young albino rats were treated either by repeated subcutaneous injections or by repeated forced feedings with dihydrotachysterol (Hytakerol) over periods ranging from 7 to 30 days, total dosage of the drug varying from .31 to 5.5 mg. The histological alterations in the long bones resulting from this treatment have been described. Significant changes were induced with relatively lower dosage when the drug was given by stomach tube but with either method were in direct proportion to the total dosage and duration of the experiment. The most striking changes consisted of the appearance of extensive channels, wide passageways and cystic cavities extending varying distances from the endosteal toward the periosteal surfaces of the cortex of the long bones. After prolonged oral administration most of the shaft was reduced to a trabecular meshwork. Some of these spaces were occupied by highly vascular hemopoietic tissue, with some infiltration of fibroblastic cellular tissue. Infrequently at the distal ends of these spaces, large multinucleated osteoclasts were found. With chronic oral treatment of a 10-day period only minor irregularities were encountered on the endosteal surface and a thin layer of osteoid tissue, apparently recently deposited, was present.