Effects of doxycycline on the development of bone damage caused by prednisolone in rats

The aim of the present study was to investigate the effects of doxycycline on the development of bone damage caused by prednisolone in rats. The experiments were carried out on male WAG rats (200-260 g), divided into 2 control and 6 experimental groups receiving prednisolone (5 mg/kg im daily) or/and doxycycline (100 mg/kg po daily) for 2 or 4 weeks. The animals were sacrificed on the 15th or 29th day of the experiment and the following characteristics were examined: mass, length, mechanical properties, mineral and calcium content in the tibia and femur, width of endosteal and periosteal osteoid, endosteal and periosteal transverse growth, transverse cross-section area of the diaphysis and of the marrow cavity in the tibia, width of epiphyseal cartilage and width of trabeculae in the femur. Prednisolone caused features of osteopenia (inhibition of bone formation and intensification of bone resorption), which were stronger after 4 weeks of the experiment. Doxycycline administered alone for 2 or 4 weeks intensified the processes of bone formation and resorption. Doxycycline to some degree attenuated the influence of prednisolone on rat bones.