Early stage of urolithiasis formation in experimental hyperparathyroidism

Purpose: We have previously noted marked acceleration in the proliferative activity of parathyroid cells in rats with spontaneous hypercholesterolemia and secondary hyperparathyroidism. Using this proliferative potential we i nvestigated whether transplantation of these enlarged parathyroids into nor mal rats would induce hyperparathyroidism and renal stones. Materials and Methods: We used 26-week-old male rats with spontaneous hyper cholesterolemia as donors, and 5-week-old normal male Sprague-Dawley rats a nd rats with spontaneous hypercholesterolemia as recipients. Enlarged parat hyroid glands were transplanted into group 1-Sprague-Dawley rats with no tr eatment, group 2-Sprague-Dawley rats that received FK-506 as an immune-supp ressor, group 3-rats with spontaneous hypercholesterolemia rats that underw ent parathyroidectomy plus FK-506 administration and group 4-Sprague-Dawley rats that underwent parathyroidectomy plus FK-506 administration. Parathyr oidectomy was performed in recipients before transplantation to ensure a lo w calcium condition. Results: Crafts were rejected within 11 and 15 weeks in groups 1 and 2, res pectively. In group 3, 78% of the grafts were successful even after 19 week s. In group 4 graft survival was 30% at 15 weeks with complete rejection at 19 weeks. In group 3 gradually elevated serum parathyroid hormone was obse rved as well as stone plaques containing calcium oxalate and calcium phosph ate in renal tubules located mainly in the corticomedullary junction. An in creased number of plaques was associated with higher parathyroid hormone. Conclusions: Our study shows that transplanted parathyroid glands function with an immunosuppressive agent and the maintenance of hypocalcemic conditi ons, and they secrete sufficient parathyroid hormone to demonstrate hyperpa rathyroidism. Plaque in these kidneys indicates an early stage of urolithia sis caused by hyperparathyroidism.