Electrophoretically separated bone cell types from the foetal rat calvarium: a histochemical and biochemical study.

Isolated cells obtained from foetal rat bone (calvarium) by collagenase digestion can be separated into three subpopulations on the basis of surface charge by free flow electrophoresis. These subpopulations have been tentatively identified by numerical, biochemical and functional criteria and are believed to be composed of: (1) bone resorbing cell types, designated Peak I cells; (2) fibroblasts and loose connective tissue cells, designated Peak II cells; and (3) a mixture of osteoblasts and osteoprogenitor cell types, designated Peak III cells. The anatomical position of these subpopulations in the whole calvarium was determined by comparing the results of histochemical and morphological experiments with the results of biochemical experiments. It was found that Peak I cells are located predominantly on the ventral (endocranial) surface, Peak II cells in the connective tissue periosteal membranes and Peak III cells on the dorsal (ectocranial) surface and in the suture line areas. The response of these cell types to parathyroid hormone and calcitonin with regard to c amp production and 45Ca release from devitalized bone is examined and indicates that cells from Peak I and Peak III both respond to parathyroid hormone but only the cells from Peak I respond to calcitonin.