A discrepancy between measurements of bone resorption in vivo and in vitro in newborn osteopetrotic rats

✍ Scribed by Marks, Sandy C.

• Publisher: Wiley (John Wiley & Sons)
• Year: 1974
• Tongue: English
• Weight: 951 KB
• Volume: 141
• Category: Article
• ISSN: 0002-9106
• DOI: 10.1002/aja.1001410305

✦ Synopsis

Abstract

Bone resorption in newborn osteopetrotic rats and their normal littermates was measured in vivo and in vitro with different results. The resorption measured in vivo was that induced by injection of parathyroid extract after labeling bone matrix with ^3^H. Resorption was measured in vitro, by a commonly used method, as the release into the culture medium of ^45^Ca and ^3^H previously incorporated in vivo into bone mineral and matrix respectively. In osteopetrotic rats resorption induced by parathyroid extract in vivo was 34 percent less than in littermate controls, whereas the resorption measured in vitro was 26 percent greater in bone from osteopetrotic rats. In addition, the hypercalcemia induced by injections of parathyroid extract was only half as great in osteopetrotic rats as in normal littermates.

Acid phosphatase appears to be important in bone resorption; osteoclasts are rich in the enzyme and it is released from them during bone resorption. Newborn osteopetrotic rats have more osteoclasts which are richer in acid phosphatase than normal littermates. Therefore, it is proposed that the enhanced resorption found in bone from osteopetrotic rats in vitro is the result of release of this excessive acid phosphatase from osteoclasts under the conditions of culture and does not truly reflect resorption in vivo.