Possible role of nerve impulse induced sodium ion flux in a proposed multivesicular fractional release of adrenaline and noradrenaline from the chromaffin cell.
Based on own observations concerning a two-compartment storage of CA in the adrenal medulla and a cation exchange dependent release of CA from perfused chromaffin granules in vitro, and encouraged by recent reports from other laboratories about the importance of sodium ions for the CA release from the adrenal gland, we propose a modification of the current quantal theory of CA secretion. Instead of secretion of quanta, each quantum corresponding to the content of one vesicle, we envisage a concomitant fractional release of CA from multiple vesicles adjacent to the chromaffin cell membrane. The CA secretion should be the result of a cation exchange across the contact area between the plasma membrane and the granule membrane during the period of depolarization caused by the nerve impulse. The size of the released quanta should be determined by the nerve impulse induced sodium ion flux and the number of such ions which reach the CA binding ionic sites in the cation exchanger pool (the release pool) of the granules.
D000313:Adrenal Medulla / Q000378:metabolism*; D002838:Chromaffin System / Q000378:metabolism*; D004837:Epinephrine / Q000378:metabolism*; D005089:Exocytosis; D007477:Ions; D008954:Models, Biological; D009431:Neural Conduction; D009638:Norepinephrine / Q000378:metabolism*; D012964:Sodium / Q000502:physiology*; D013153:Splanchnic Nerves / Q000502:physiology
D007477:Ions; D012964:Sodium; D009638:Norepinephrine; D004837:Epinephrine