Effects of insulin and 1 alpha-hydroxy vitamin D3 on streptozotocin-induced diabetic rats fed a low zinc diet.

Streptozotocin-induced diabetic rats (LZ-DM rats) developed nephrocalcinosis after being fed a low zinc diet for 4 weeks. However, administration of 1 alpha-hydroxy vitamin D3 (1-OHD3) or insulin inhibited the formation of nephrocalcinosis. The urinary calcium level increased when 1-OHD3 was administered to these rats, but decreased in the group receiving insulin. It was also observed that the femur recovered its hardness when insulin was administered, although the hardness in the LZ-DM rats remained lower than that of the control rats. Rat femur hardness, however, did not completely recover with 1-OHD3 treatment. These results indicate that the effects of insulin and 1-OHD3 differ, even though nephrocalcinosis was reduced by administration of either insulin or 1-OHD3. It appears that insulin assists bone formation, and the 1-OHD3 hastens calcium excretion.