Abstract
Summary
A method for quantitative determination of amount of osteoclast material in rat femurs is presented. The number of osteoclasts/unit area is sufficiently constant in normal animals to permit statistical differentiation between these and experimental groups. Parathyroidectomy reduced the osteoclast count, which was subsequently returned to normal by parathyroid extract administration. Nephrectomy, continuous peritoneal lavage, and parathyroid extract administration to normal animals, all increased significantly the number of osteoclasts/unit area. Maintenance of a normal osteoclast concentration above that of parathyroidectomized animals is discussed in relation to McLean's “feed-back’ principle of parathyroid action under which continuous secretory activity of these glands is assumed. It is felt that determination of osteoclast concentrations as described can be used as index of parathyroid activity in studying problems related to parathyroid secretion.
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