The mechanism by which tetracycline hydrochloride inhibits mineralization in vitro.

Abstract

Abstract 1. 1. The inhibitory action of tetracycline hydrochloride on mineralization was demonstrated in vitro . Low concentrations of the drug interfered with teh precipitation of apatites from supersaturated mineralization buffers at 37° and pH 7.4. In the presence of 20 μM tetracycline, the ionic produce of calcium and phosphate required for spontaneous precipitation rose from 2.5 to 4.0 (mM) 2 . The amount of mineral in the precipitate was not altered, which suggests that tetracycline affects the primary nucleation of mineralization. 2. 2. In metastable mineralization buffers tetracycline also depressed the uptake of minerals by extracted fibers of collagen X-ray diffraction studies showed that the crystalline structure of the apatites formed in the collagen was not disturbed by the drug. The binding of radio-labeled tetracycline to the collagen was closely associated with the mineralization of the collagen. 3. 3. Finally, in a kinetic model of the mineralization induced by collagen, the two phases of apatite formation, nucleation and crystal growth, could be dissociated. In the experimental conditions used, 20 μM tetracycline depressed nucleation to about half and crystal growth to about one-third of the control values. 4. 4. It is concluded that inhibition of mineralization by antibiotics of the tetracycline group during osteogenesis and tooth formation may be due to mechanisms similar to those operating during the experimental mineralization demonstrated in the present study.