Effect of estriol on bone collagen of rats with experimental osteoporosis.

Abstract

The inhibitory effect of estriol on the development of experimental osteoporosis produced by low calcium diet was studied through the analysis of calcium content and amino acid composition of insoluble collagen of the femurs and tibiae. A marked decrease in the calcium content of bones was significantly prevented by the simultaneous daily oral administration of 40μg estriol. Although lysine, hydroxylysine and sum of lysine and hydroxylysine in the insoluble collagen of bones in low calcium-fed rats were increased when compared with those in control, these values were decreased by the simultaneous administration of estriol, compared with those in low calcium-fed rats. The simultaneous daily oral administration of 300μg estriol to low calcium-fed rats showed no statistical difference against control, in the sum of lysine and hydroxylysine. The changes of these amino acids suggest some alteration of crosslinks in collagen.The biochemical structure of collagen has been elucidated recently. However, the mechanism of calcification in relation to the minute changes in collagen structure is not yet clear. The effect of estriol on collagen and the protecting effect of estriol against the loss of bone mineral suggest the relation of molecular structure of collagen with calcification.