Effects of caffeine on bone cells and bone development in fast-growing rats

Caffeine exerts harmful effects on fetal and suckling rats. To elucidate the effects of caffeine on bone in growing rats further, dams were fed normal laboratory chow until delivery. At birth, the litters were combined and eight pups were randomly assigned to each dam. Dams with the combined litters were divided into two groups. Dams of group 1 received a 20% protein diet as a control, and dams of group 2 received the 20% protein diet supplemented with caffeine (4 mg/100 g b.w.). Pups from both groups were killed on days 11, 15, 22, and 50. Parameters studied were ultrastructure of femoral osteoblasts, osteocytes, and osteoclasts; the number of osteocytes per area of bone in femoral histological cross sections; structural remodeling and shape of the lateral tibial metaphysis as revealed by scanning electron microscopy; and plasma Cu and Zn concentrations.

Rats in the caffeine groups had significantly fewer osteocytes per area of femoral cross section, retarded structural remodeling of the lateral tibial metaphysis, osteoblasts and osteocytes with disrupted swollen mitochondria, and decreased plasma Cu and Zn levels when compared with controls.

These results indicate that if young, rapidly growing rats are exposed to caffeine, disruption of osteoblasts and retarded bone development occur, which could be related to the decreased plasma Cu level in the young animals.