Na+-Ca2+ exchange in the axolemma-rich membrane vesicle preparations from the walking-leg nerves of the American lobster.
An axolemma-rich membrane vesicle fraction was prepared from the leg nerve of the lobster, Homerus americanus. In this preparation Ca2+ transport across the membrane was shown to require a Na+ gradient (Na+-Ca2+ exchange), and external K+ was found to facilitate this Na+-Ca2+ exchange activity. In addition, at high Ca2+ concentrations (20 mM) a Ca2+-Ca2+ exchange system was shown to operate, which is stimulated by Li+. The Na+-Ca2+ exchange system is capable of operating in the reverse direction, with Ca2+ uptake coupled with Na+ efflux. Such a vesicular preparation has the potential for providing useful experimental approaches to study the mechanism of this important Ca2+ extrusion system in the nervous system.
D000818:Animals; D001369:Axons / Q000378:metabolism*; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D007700:Kinetics; D008121:Nephropidae; D010525:Peripheral Nerves / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger
D002352:Carrier Proteins; D019831:Sodium-Calcium Exchanger; D012964:Sodium; D002118:Calcium