Effect of administration of retinol and etidronate on bone histomorphometric parameters in ovariectomized rats

Retinol belongs to factors affecting bone remodeling. The effect of retinol on the osseous tissue depends on the dose and duration of treatment. Retinol can cause bone damage and deformation. Retinol is frequently administered chronically in too high doses, sometimes by osteoporotic patients. The aim of the present study was to examine the interaction between retinol and an antiresorptive drug--disodium etidronate in bilaterally ovariectomized rats. The experiments were carried out on Wistar rats (200 +/- 30 g), divided into 7 groups: I--sham operated control rats. II--ovariectomized control rats (OVX), III--OVX + editronate (10 mg/kg p.o.), IV--OVX + retinol (700 IU/kg p.o.). V--OVX + retinol (3500) IU/kg p.o.), VI--OVX + etidronate (10 mg/kg p.o.) + retinol (700 IU/kg p.o.), VII--OVX + etidronate (10 mg/kg p.o.) + retinol (3500 IU/kg p.o.). The drugs were administered for 4 weeks. Bone macrometric and histomorphometric parameters of the tibia (transverse growth, width of periosteal and endosteal osteoid, area of the transverse cross-section of the diaphysis and area of the transverse cross-section of the marrow cavity) and the femur (width of epiphyseal and metaphyseal trabeculae, width of epiphyseal cartilage) were examined. Editronate partially counteracted the development of changes induced by ovariectomy. Retinol (700 IU/kg p.o.) caused decreases in the area of the transverse cross-section of the marrow cavity and the width of osteoid, and an increase in the width of trabeculae. Retinol (3500 IU/kg p.o.) caused decreases in bone mass and the area of the transverse corss-section of the marrow cavity, and an increase in the width of trabecula. Concurrent administration of etidronate and retinol in ovariectomized rats seemed not to affect bone histomorphometric parameters in a way suggesting any interaction between them.