Possible role of H+--alkali cation countertransport in secretory granule swelling during exocytosis.
Studies in model systems, as well as observations in intact cells, suggest that osmotic swelling of secretory granules is an essential step in exocytosis. A model is proposed whereby the low pH recorded in most secretory organelles could provide the driving force for granule swelling. The model assumes that during stimulation an exchange of H+ for alkali cations is triggered across the granule membrane. The outgoing H+ are rapidly replaced by the internal buffering capacity with a concomitant osmotic gain. The exchange is independent of anions and could be triggered by cytoplasmic Ca2+. The H+ -pump is responsible for the delta pH but independent of the exchange mechanism.
D003594:Cytoplasmic Granules / Q000502:physiology*; D005089:Exocytosis; D007425:Intracellular Membranes / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism*; D008954:Models, Biological; D009997:Osmotic Pressure; D011522:Protons
D007473:Ion Channels; D011522:Protons