The meeting is cosponsored by APS, the American College of Sports Medicine and the Canadian Society for Exercise Physiology. Additional support through unrestricted educational grants came from: the National Aeronautics and Space Administration (NASA), the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMSD), Gatorade Sports Sciences Institute, Pfizer Inc. and the U.S. Army Research Institute of Environmental Medicine (USARIEM).
Mechanosensors, desensitization under study
Though the cellular mechanosensors are very efficient, Turner noted that the biological processes involved in bone mechanotransduction are poorly understood, "yet several pathways are emerging from current research." These include ion channels in the cell membrane, ATP (adenosine triphosphate) signaling, and second messengers such as prostaglandins and nitric oxide. Specific targets of mechanical loading include the L-type calcium channel (alpha 1C isoform), a gadolinium-sensitive stretch-activated channel, P2Y2 and P2X7 purinergic receptors, EP2 and EP4 prostanoid receptors, and the parathyroid hormone receptors.
"One characteristic of the mechanosensing apparatus that has only recently been studied is the important role of desensitization," Turner notes. "Experimental protocols that insert 'rest' periods to reduce the effects of desensitization can double anabolic responses to mechanical loading," he adds. Again, it's unclear how desensitization of bone cells occur, but it's an area ripe for further study.
A recent paper with his colleague, Alexander G. Robling, "Designing exercise regimens to increase bone strength," dealt with desensitization and age-related effects of exercise, among many other topics, including development of an exercise "osteo
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5-Oct-2004