Abstract
Quantitative bone histology, and serum and urinary biochemistry were studied in male SHC rats that spontaneously develop hypercholesterolemia and renal insufficiency; age-matched Sprague-Dawley (SD) rats served as controls. An increase in serum levels of urea nitrogen and inorganic phosphorus was observed in the SHC rats at the age of 15 weeks and thereafter. In 27-week-old SHC rats, an acceleration of osteoclastic bone resorption and bone formation, and increased deposition of osteoid were observed in the trabecular bone of the proximal tibial metaphysic. A peritrabecular fibrous tissue formation, myelofibrosis, was also seen in the SHC rats. The double fluorescence labeling method and contact microradiography revealed impaired mineralization of osteoid tissue in the tibial trabecular bone of SHC rats. Neither osteopenia nor osteosclerosis existed in the bone. These results indicate that the trabecular bone lesion in the SHC rats is characterized by osteitis fibrosa accompanied by osteomalacia. Analysis of the tibial shaft, on the other hand, showed decreased cortical bone area with increased marrow area, but no increased osteoid tissue.
The SHC rat spontaneously develops chronic renal failure, hyperphosphatemia, hyperparathyroidism, and metastatic calcification in soft tissues. The findings presented here indicate that these rats have bone disease resembling that of patients with renal osteodystrophy.
