Early bone lesions in the hyperparathyroidism of hyperlipidemic rats.

Hyperlipidemic rats were examined histopathologically at 10, 14, 18 and 22 weeks of age for evaluation of early bone lesions in renal secondary hyperparathyroidism. Serum chemistry revealed that the mean levels of total cholesterol, triglyceride and phospholipid were greater than the respective control levels at 10 weeks of age, and that they increased with age. The mean levels of urea nitrogen, creatinine, inorganic phosphorus and calcium were also greater than the respective control levels at and after 14 weeks of age. Grossly, the kidney showed enlargement with an irregular surface and the parathyroid gland was swollen at and after 14 weeks of age. Histologically, the bone showed proliferation and hypertrophy of osteoblasts, an increase in osteoid seams, and an increase in and irregularity of the cement lines. These changes were first seen at 14 weeks of age, and became more severe with age. In addition, osteoclasts were increased at and after 18 weeks of age, and the parathyroid gland was enlarged at and after 14 weeks of age. On the other hand, segmental glomerular sclerosis was detected at 10 weeks of age, and became more severe with increasing age.