Effects of on/off anabolic hPTH and remodelling inhibitors on metaphyseal bone of immobilized rat femurs. Tomographical (pQCT) description and correlation with histomorphometric changes in tibial cancellous bone

An anabolic effect of hPTH(1–38) (s.c. doses of 200 ug/kg/d during 75 days) on trabecular and cortical bone mass is tomographically described in the metaphyseal region of immobilized rat femurs using pQCT technology, in agreement with previous histomorphometrical studies of the proximal tibial metaphyses. Correlations between pQCT and histomorphometrical data showed that this effect derived from a stimulation of endosteal and trabecular bone modeling that induced a transference from trabecular to cortical bone mass. Loss of effects after withdrawal, resulting from a stimulation of bone remodeling, could be total or partially prevented by subsequent s.c. injections of risedronate (5 ug/kg/2/wk), 17-B-estradiol (10 ug/kg/d) or calcitonin (10 ug/kg/d) given during 60 days, in this order of effectiveness. The preventive potency was proportionally related to the reduction induced in histomorphometric indices of bone resorption.