THE EFFECT OF GALLIUM NITRATE ON HEALING OF VITAMIN-D-DEFICIENT AND PHOSPHATE-DEFICIENT RICKETS IN THE IMMATURE RAT

The effect of gallium on rapid in vivo mineralization was studied in a rachitic rat model in which rickets were induced in immature rats the n reversed (''healed'') with repletion of vitamin D and phosphate. Gal lium was administered to selected groups of animals before and during the healing phase. In nonrachitic animals and rachitic animals before healing, the mineral content of diaphyseal and metaphyseal bone was in creased, and the crystal size was decreased in those animals that rece ived gallium compared with those that did not. Mineralization of the u ndermineralized osteoid appeared histologically normal by 72 hours in all animals. However, animals that received gallium both before and du ring the healing phase had less well-mineralized bones at 18 hours, an d by 72 hours, they had lesser increases in osteocalcin and mineral co ntent, which was associated with smaller crystal sizes, than did any a nimal that did not receive gallium at any time. Prior to the healing p hase, the ratio of gallium to hydroxyproline in the metaphyses of rach itic animals was similar to that in nonrachitic animals. Likewise, thi s ratio did not change in the animals receiving gallium both before an d during the healing phase. The ratio of gallium to calcium was higher in rachitic animals compared with controls, and this ratio lowered si gnificantly by the end of the healing phase. Results may be explained in part by direct effect of gallium on the physical process of mineral formation during the rapid healing phase as well as by effects of gal lium on osteoblasts and osteoclasts during the induction of rickets.