Edwin Berryman

Impact of Mrp2 on the biliary excretion and intestinal absorption of furosemide, probenecid, and methotrexate using Eisai hyperbilirubinemic rats.

AbstractPurpose. This study assesses the impact of rat multidrug resistance-associated protein 2 (Mrp2) on the biliary excretion and oral absorption of furosemide, probenecid, and methotrexate using Eisai hyperbilirubinemic rats (EHBR). Methods. To assess Mrp2-mediated biliary excretion, rats received a 2-h intravenous infusion of furosemide, probenecid, or methotrexate. Blood and bile samples were collected at specified intervals. To assess Mrp2s impact on oral absorption, rats received furosemide, probenecid, or methotrexate orally at 5 mg/kg. Jugular and portal blood samples were obtained at timed intervals. All samples were analyzed by LC-MS/MS. Pharmacokinetic parameters were estimated using WinNonlin and standard pharmacokinetic equations. Results. Thirty seven- and 39-fold reductions in biliary clearance were observed in EHBR as compared to control rats for probenecid and methotrexate, respectively. Biliary clearance was comparable between EHBR and control rats for furosemide. In all cases, no significant difference in absorption was observed between EHBR and control rats. Conclusions. This study provides the first evidence that Mrp2 mediates the biliary excretion of probenecid but not furosemide. Additionally, Mrp2 apparently has a less profound impact on intestinal absorption than biliary excretion of its substrates. Furthermore, alteration in systemic clearance in EHBR indicates that a potential compensatory mechanism may occur in EHBR.

Age-related Changes in Marmoset Trabecular and Cortical Bone and Response to Alendronate Therapy Resemble Human Bone Physiology and Architecture

In older humans, bone elongation ceases, periosteal expansion continues, and bone remodeling remains a dominant metabolic process. An appropriate animal model of type I and type II osteoporosis would be a species with sealed growth plates and persistence of bone remodeling. The rat is commonly used as a primary model, but due to delayed epiphyseal closure with continuous modeling and lack of Haversian remodeling, Food and Drug Administration guidelines recommend assessment of bone quality in an additional, nonrodent, remodeling species. This study investigated the skeletal characteristics of senescent marmosets to evaluate their suitability as an osteoporosis model. Animals were randomized across three experimental groups; controls for both sexes and marmosets receiving alendronate for either 30 or 60 days (28 μg/kg, sc, twice per week). Outcome measures included serum chemistry and bone biomarkers, DEXA, histomorphometry, micro‐computed tomography, and histopathology. Results showed that the adult marmoset skeleton has similar anatomical characteristics to the adult human, including the absence of growth plates, presence of Haversian system, and true remodeling of cancellous and cortical bone. Structural analyses of senescent marmoset cancellous bone demonstrated loss of trabecular mass and architecture similar to skeletal changes described for elderly men and women. Treatment with alendronate improved trabecular volume and number by reducing bone resorption, although bone formation was also reduced through coupling of bone remodeling. The common marmoset may provide a valuable model for research paradigms targeting human bone pathology and osteoporosis due to skeletal features that are similar to age‐related changes and response to bisphosphonate therapy reported for humans. Anat Rec, 2007.

Correlation between μCT imaging, histology and functional capacity of the osteoarthritic knee in the rat model of osteoarthritis

BackgroundTo acquire the most meaningful understanding of human arthritis, it is essential to select the disease model and methodology translatable to human conditions. The primary objective of this study was to evaluate a number of analytic techniques and biomarkers for their ability to accurately gauge bone and cartilage morphology and metabolism in the medial meniscal tear (MMT) model of osteoarthritis (OA).MethodsMMT surgery was performed in rats to induce OA. A dynamic weight bearing system (DWB) system was deployed to evaluate the weight-bearing capacity of the front and hind legs in rats. At the end of a 10-week study cartilage pathology was evaluated by micro computed tomography (μCT), contrast enhanced μCT (EPIC μCT) imaging and traditional histology. Bone tissue was evaluated at the tibial metaphysis and epiphysis, including the subchondral bone. Histological techniques and dynamic histomorphometry were used to evaluate cartilage morphology and bone mineralization.ResultsThe study results showed a negative impact of MMT surgery on the weight-bearing capacity of the operated limb. Surgery caused severe and extensive deterioration of the articular cartilage at the medial tibial plateau, as evidenced by elevated CTX-II in serum, EPIC μCT and histology. Bone analysis by μCT showed thickening of the subchondral bone beneath the damaged cartilage, loss of cancellous bone at the metaphysis and active osteophyte formation.ConclusionsThe study emphasizes the need for using various methodologies that complement each other to provide a comprehensive understanding of the pathophysiology of OA at the organ, tissue and cellular levels. Results from this study suggest that use of histology, μCT and EPIC μCT, and functional DWB tests provide powerful combination to fully assess the key aspects of OA and enhance data interpretation.

Effect of antiresorptive and anabolic bone therapy on development of osteoarthritis in a posttraumatic rat model of OA

IntroductionOsteoarthritis (OA) is a leading cause of disability, but despite the high unmet clinical need and extensive research seeking dependable therapeutic interventions, no proven disease-modifying treatment for OA is currently available. Due to the close interaction and interplay between the articular cartilage and the subchondral bone plate, it has been hypothesized that antiresorptive drugs can also reduce cartilage degradation, inhibit excessive turnover of the subchondral bone plate, prevent osteophyte formation, and/or that bone anabolic drugs might also stimulate cartilage synthesis by chondrocytes and preserve cartilage integrity. The benefit of intensive zoledronate (Zol) and parathyroid hormone (PTH) therapy for bone and cartilage metabolism was evaluated in a rat model of OA.MethodsMedial meniscectomy (MM) was used to induce OA in male Lewis rats. Therapy with Zol and human PTH was initiated immediately after surgery. A dynamic weight-bearing (DWB) system was deployed to evaluate the weight-bearing capacity of the front and hind legs. At the end of the 10-week study, the rats were euthanized and the cartilage pathology was evaluated by contrast (Hexabrix)-enhanced μCT imaging and traditional histology. Bone tissue was evaluated at the tibial metaphysis and epiphysis, including the subchondral bone. Histological techniques and dynamic histomorphometry were used to evaluate cartilage morphology and bone mineralization.ResultsThe results of this study highlight the complex changes in bone metabolism in different bone compartments influenced by local factors, including inflammation, pain and mechanical loads. Surgery caused severe and extensive deterioration of the articular cartilage at the medial tibial plateau, as evidenced by contrast-enhanced μCT and histology. The study results showed the negative impact of MM surgery on the weight-bearing capacity of the operated limb, which was not corrected by treatment. Although both Zol and PTH improved subchondral bone mass and Zol reduced serum CTX-II level, both treatments failed to prevent or correct cartilage deterioration, osteophyte formation and mechanical incapacity.ConclusionsThe various methods utilized in this study showed that aggressive treatment with Zol and PTH did not have the capacity to prevent or correct the deterioration of the hyaline cartilage, thickening of the subchondral bone plate, osteophyte formation or the mechanical incapacity of the osteoarthritic knee.

A novel endpoint for the assessment of chemotherapy‐induced peripheral neuropathy in rodents: biomechanical properties of peripheral nerve

Chemotherapy‐induced peripheral neuropathy (CiPN) is a frequent adverse effect in patients and a leading safety consideration in oncology drug development. Although behavioral assessment and microscopic examination of the nerves and dorsal root ganglia can be incorporated into toxicity studies to assess CiPN risk, more sensitive and less labor‐intensive endpoints are often lacking. In this study, rats and mice administered vincristine (75 μg kg−1 day−1, i.p., for 10 days in rats and 100 μg kg−1 day−1, i.p., for 11 days in mice, respectively) were employed as the CiPN models. Behavioral changes were assessed during the dosing phase. At necropsy, the sural or sciatic nerve was harvested from the rats and mice, respectively, and assessed for mechanical and histopathological endpoints. It was found that the maximal load and the load/extension ratio were significantly decreased in the nerves collected from the animals dosed with vincristine compared with the vehicle‐treated animals (P < 0.05). Additionally, the gait analysis revealed that the paw print areas were significantly increased in mice (P < 0.01), but not in rats following vincristine administration. Light microscopic histopathology of the nerves and dorsal root ganglia were unaffected by vincristine administration. We concluded that ex vivo mechanical properties of the nerves is a sensitive endpoint, providing a new method to predict CiPN in rodent. Gait analysis may also be a useful tool in these pre‐clinical animal models.