Usefulness of biochemical markers of bone turnover in rats after clodronate administration

Dichloromethylene bisphosphonate (clodronate), an inhibitor of bone resorption, has been administered subcutaneously (1.25 mg/day, 3 consecutive days) to control male albino Wistar rats (n = 8). Variations in the levels of serum alkaline phosphatase (AP) and osteocalcin (BGP), biochemical markers of bone formation, and in urinary hydroxyproline (OH-Prol) and serum tartrate-resistant acid phosphatase (TRAP), markers of bone resorption, have been analyzed. A significant decrease was observed in OH-Prol/creatinine and TRAP. We found a positive correlation between the percentage of decrease, with respect to basal values, of TRAP and OH-Prol/creatinine (p < 0.05). These results suggest that TRAP could be a useful marker to evaluate the changes of bone resorption induced by bisphosphonates in the rat together with the classical marker OH-Prol. A significant decrease was observed in AP. BGP also decreased significantly, but the decrease was relatively small compared to the coefficient of variation of the method. We suggest the preferential use of AP determination, instead of BGP, in the study of the effects produced by bisphosphonates on bone formation in rats, if hepatic function is maintained.