The effect of marine alga
Sargassum horneri extracts on bone resorption
in vitro was investigated. Femoral-diaphyseal and -metaphyseal tissues obtained from normal rats were cultured for 48 hr in Dulbecco's modified Eagle's medium (high glucose, 4.5%) supplemented with antibiotics and bovine serum albumin. The experimental cultures contained water-solubilized extracts (10, 25, and 50
μg/ml of medium) of
S. horneri. The bone-resorbing factors parathyroid hormone (1-34) (PTH; 10
-7 M) and prostaglandin E
2 (PGE
2; 10
-5 M) caused a significant decrease in the diaphyseal and metaphyseal calcium content. The decrease in bone calcium content induced by PTH or PGE
2 was completely inhibited by water-solubilized extracts (10, 25, and 50
μg/ml) of S. horneri. In addition, these extracts (25 and 50
μg/ml) completely prevented the PTH (10
-7 M)- or PGE
2 (10
-5 M)-induced increase in medium glucose consumption and lactic acid production by bone tissues. Moreover, S. horneri extracts (10-50
μg/ml) blocked PTH (10
-7 M)- increased acid phosphatase activity in the diaphyseal and metaphyseal tissues. These findings indicate that water-solubilized extracts of
S. horneri have a direct inhibitory effect on bone resorption in tissue culture
in vitro.
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