MECHANICAL-PROPERTIES, BONE-MINERAL CONTENT, AND BONE-COMPOSITION (COLLAGEN, OSTEOCALCIN, IGF-I) OF THE RAT FEMUR - INFLUENCE OF OVARIECTOMY AND NANDROLONE DECANOATE (ANABOLIC-STEROID) TREATMENT

Nandrolone decanoate (ND) is an anabolic steroid with a positive effec t on bone mass in osteoporotic patients. The mechanism of action, (i.e ., reduction of bone resorption and/or stimulation of bone formation), the ultimate effect on mechanical properties, and the most effective dosage are not yet clear. To address these issues, dose-related effect s of the long-term effect of ND on serum and bone biochemistry, bone m ineral content, and bone mechanical properties in ovariectomized (OVX) rats (12 weeks old at the start of the experiment) were studied for 6 months. The results were compared with those obtained in age-matched, intact, and OVX rats. OVX caused in the femur a significant increase in net periosteal bone formation and net endosteal bone resorption of bone collagen content and torsional strength, and of serum alkaline ph osphatase, osteocalcin, and insulin-like growth factor-I (IGF-I) level s, whereas cortical bone density and calcium/creatinine and phosphorus /creatinine in 24-hour urine were significantly reduced. Treatment of OVX rats with 1 mg ND/14 days resulted in a significant increase in pe riosteal bone formation, femur length, cortical and trabecular bone mi neral content and density, torsion stiffness and strength, and bone IG F-I content, and a decrease in serum osteocalcin, urinary calcium/crea tinine levels, and bone collagen content compared with OVX controls. T he higher ND dosage of 2.5 mg/14 days did not improve the results. ND treatment did not reverse all changes induced by OVX to the level of t he intact controls. These results indicate that ND acts as an antireso rptive drug and as a bone formation stimulating drug. Furthermore, the increased bone mass and bone mineral density is associated with impro ved bone strength and stiffness and the presence of an increased amoun t of IGF-I. IGF-I is a growth factor considered to play a role in the maintenance of normal skeletal balance by a paracrine or autocrine mec hanism.