Intracellular transport of calcium and its relationship to homeostasis and mineralization: An electron microscope study

• Published in: The American journal of medicine Vol. 50; no. 5; pp. 589 - 597
• Main Authors: Matthews, J.L., Martin, J.H.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.05.1971
• Subjects: Biological Transport; Bone and Bones - cytology; Bone and Bones - metabolism; Calcium - metabolism; Cell Membrane Permeability; Homeostasis; Humans; Microscopy, Electron; Mitochondria - physiology; Osteoblasts - cytology; Osteoclasts - cytology; Osteocytes - cytology
• ISSN: 0002-9343; 1555-7162
• DOI: 10.1016/0002-9343(71)90114-8

Electron microscopy of undemineralized bone reveals details of its ultramicro-architecture and histology. Based on the presence, subcellular localization and apparent movement of calcium under hormonal influences, a concept of the dynamic function of bone in extracellular calcium homeostasis is proposed. In this scheme the osteocyte is considered to be centrally important in that it responds rapidly to stimuli, is critically positioned and is anatomically capable of “communicating” with osteoblasts and the vascular system by an extensive net of cell processes or canaliculi. Calcium gains entry from the extracellular fluid bathing osteocytes by passing between adjoining osteoblasts, whereas osteoblasts are polarized and continuously extrude calcium into the interstitial fluid on their vascular side. Osteocytes can accumulate or extrude calcium, depending on their microenvironment and on hormonal factors, and can therefore be considered to be ideally suited to effect rapid changes in extracellular fluid calcium concentrations. The osteoclast is regarded primarily as being responsible for large-scale bone remodeling.