Ca(2+)-independent regulation of neurosecretion by intracellular Na+.
While secretion from nerve endings is strictly controlled by an increase in cytoplasmic free calcium several reports suggest intracellular sodium may serve a regulatory role. Whether sodium acts directly to modulate secretion or indirectly by influencing cytoplasmic calcium dynamics is unknown. This study shows, based on parallel experiments studying [Na+]i, [Ca2+]i and vasopressin secretion, that sodium acts directly to regulate secretion in isolated nerve endings from the rat neurohypophysis. The elevation in secretion that develops is dose-dependently related to the [Na+]i and can occur in the absence of changes in [Ca2+]i.
Nordmann
J J
JJ
Centre de Neurochimie CNRS, Strasbourg, France.
Stuenkel
E L
EL
D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D004072:Digitonin / Q000737:chemistry; D066298:In Vitro Techniques; D008564:Membrane Potentials; D009411:Nerve Endings / Q000378:metabolism* / Q000502:physiology; D010902:Pituitary Gland / Q000378:metabolism; D051381:Rats; D012964:Sodium / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
D001127:Arginine Vasopressin; D012964:Sodium; D004072:Digitonin; D002118:Calcium