Bisphosphonates (BP), drugs that inhibit bone resorption, are used to minimize bone loss in long-duration spaceflight, extended bed rest, and acute spinal cord injury; however, the long term impact of BP use on recovery of bone after disuse is not well understood. This experiment tests the hypothesis that the BP zoledronic acid (ZOL) administered 7 days before hindlimb unloading (HU) will protect against loss of bone mass during 28 days of HU by suppressing bone resorption activity while also diminishing the ability of cancellous bone formation rate (BFR) to recover following HU. Male Sprague Dawley rats (6 mo) were assigned to aging control (AC), HU, and HU+ZOL groups and subjected to 28 days of HU, then to 56 days of weight-bearing recovery (REC). One group of rats was given 2 fluorescent labels 7 days apart to measure BFR in the final week of HU and the other group was given the same labels in the final week of REC. Histomorphometric analyses of the proximal tibia and distal femur showed lower osteoclast surface, a measure of bone resorption, 35 days after injection and 119 days after injection (-50% and -75%, respectively, compared to HU). This verified that ZOL successfully suppressed bone resorption. Dynamic histomorphometry revealed that cancellous BFR was lower in ZOL+HU versus AC both immediately after HU (-96.6%) and after the recovery period (-99.9%) (p



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.