Effects of 1,25(OH)2D3 on turnover, mineralization, and strength of bone in growing rats with liver cirrhosis induced by administration of carbon tetrachloride.

To clarify the effects of 1 alpha,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) on bone growth, strength, and turnover in growing rats with liver cirrhosis induced by carbon tetrachloride (CCl(4)) injection, groups of 4-week-old male Wistar rats (n = 10, each) were injected intraperitoneally with CCl(4) twice weekly for 7 weeks. One group was treated with the vehicle alone (Group 1). Three CCl(4)-injected groups were orally administered 1,25(OH)(2)D(3) at doses of 0, 0.05, and 0.1 micro g/kg, respectively (Groups 2, 3, and 4). At the end, serum levels of 1,25(OH)(2)D(3), IGF-I, and osteocalcin were reduced in Group 2 compared to Group 1, and the corresponding values in Group 4 were larger than those in Group 2. Urinary deoxypyridinoline levels increased in Group 2 compared to Group 1, and did not significantly differ in Groups 2-4. The values for bone sizes, mineral content (BMC) in the lumbar vertebra and femur, and ultimate bending load in the femur were reduced in Group 2 compared to Group 1, and lumbar BMC in Group 3 and bone sizes in Group 4 were larger than those in Group 2. The values for lumbar trabecular bone volume in Group 2 were reduced compared to Group 1, and the corresponding values in Group 4 were larger than those in Group 2. Bone formation rates, reduced in Group 2 compared to Group 1, did not differ in Groups 2-4. Parameters for trabecular osteoclasts did not differ among all groups. In the proximal tibia, the value of activation frequency (Ac.f) in Group 2 significantly decreased compared to Group 1. Ac.f values in Groups 3 and 4 were larger than that in Group 2. These data demonstrated that retardation of bone growth in CCl(4)-injected rats was associated with reduced serum 1,25(OH)(2)D(3) and IGF-I levels. The trabecular bone in the rats exhibited low turnover osteopenia. 1,25(OH)(2)D(3) administration partially prevented the growth disturbance, but did not substantially affect bone turnover. Factors other than 1,25(OH)(2)D(3) and IGF-I appeared to be critical in the low turnover osteopenia evident in liver cirrhosis.