A histomorphometric study on effects of single and concurrent intermittent administration of human PTH (1–34) and bisphosphonate cimadronate on tibial metaphysis in ovariectomized rats

This study compared the single administration of hPTH(1–34), bisphosphonate cimadronate (YM-175), and concurrent therapy of these two for restoration of lost bone mass in ovariectomized (OVX) rats. Animals were untreated for 4 weeks after surgery, and then injected s.c. with vehicle (OVX+V), hPTH(1–34) (30 μg/kg) (OVX+P), YM-175 (5 μg/kg) (OVX+Y), or a combination of these two (OVX+P+Y), 3 days a week, for 8 weeks, and sacrificed. Their proximal tibia were processed undecalcified for quantitative bone histomorphometry. Although OVX+Y showed a reduction of bone turnover compared to OVX+V, it failed to restore lost bone mass in OVX rats. In contrast, OVX+P exhibited a stimulation of bone formation and restored cancellous osteopenia due to OVX. OVX+P+Y also resulted a recovery of osteopenia, however, stimulation of bone formation by PTH was suppressed by YM-175.