Alendronate prevents development of the skeletal changes induced by azathioprine in rats.

Immunosuppressive drugs are known to disturb bone remodeling. Azathioprine (AZA) is a potent immunosuppressive drug, but its effect on the skeletal system has not been reported so far. The aim of the present study was to investigate the effect of AZA on the rat bone remodeling, and the effect of alendronate on development of skeletal changes induced by AZA. The experiments were carried out on 3-month-old male Wistar rats, divided into the following groups: C - control rats (distilled water), AZA - azathioprine, ALN - alendronate, AZA + ALN - azathioprine and alendronate. Azathioprine (4 mg/kg po), alendronate (3 mg/kg po) and distilled water (2 ml/kg po) were administered once daily for 28 days. Bone remodeling was estimated based on quantitative and histomorphometric evaluation of the tibia and femur, and the mechanical properties of the femur and femoral neck. AZA at a dose of 4 mg/kg for 28 days induced bone remodeling disorders, inhibiting bone formation and mineralization. Alendronate prevented the development of skeletal changes caused by AZA administration, inhibiting bone resorption and increasing bone mineralization.