Effect of Risedronate on Bone Mass, Remodelling and Biomechanical Strength in Orchidectomized Rats

Background: The ability of risedronate to prevent and/or treat orchidectomy-induced osteoporosis in male rats was studied. Methods: Ninety-five 10-week-old male Wistar rats were sham-operated or orchidectomized. Prevention study: Sham: sham-operated rats; ORX: orchidectomized rats; ORX + RSD: orchidectomized rats, treated for 6 weeks with risedronate. Animals were sacrificed 6 weeks after surgery. Treatment study: Sham 1 and ORX 1 : sham and orchidectomized rats sacrificed 3 months after orchidectomy; Sham 2 , ORX 2 and ORX 2 + RSD: sham-operated, and orchidectomized rats treated with placebo or risedronate for 6 weeks starting 3 months after orchidectomy, and then sacrificed. Risedronate (0.5 mg/kg/day) and placebo (saline) were administered via oral gavage. After sacrifice, bone mineral density by DEXA, bone volume (BV/TV), osteocalcin (BGP), and serum carboxyterminal telopeptide of collagen type I (CTX) were measured. Femur low-rate torsion testing was performed. Results:Orchidectomy produced an increase in bone remodelling with loss of BV/TV, without effects on torsional strength. Risedronate treatment partially prevented these effects. In the treatment study, risedronate reduced bone remodelling and restored BV/TV to levels higher than those of the sham group, improving biomechanical parameters. Conclusions: These results suggest that risedronate could be used as a prevention or treatment of male osteoporosis due to hypogonadism.