Localization and regulation of Ca2+ entry and exit pathways in exocrine gland cells.
Studies of Ca2+ transport pathways in exocrine gland cells have been useful, chiefly because of the polarized nature of the secretory epithelial cells. In pancreatic acinar cells, for example, Ca2+ reloading of empty intracellular stores can occur solely via Ca2+ entry through the basal part of the plasma membrane. On the other hand, the principal site for intracellular Ca2+ release-with the highest concentration of inositol 1,4,5-trisphosphate (IP(3)) receptors-is in the apical secretory pole close to the apical plasma membrane. This apical part of the plasma membrane contains the highest density of Ca2+ pumps and is therefore the principal site for Ca2+ extrusion. On the basis of the known properties of Ca2+ entry and exit pathways in exocrine gland cells, the mechanisms controlling Ca2+ exit and entry are discussed in relation to recent direct information about Ca2+ transport into and out of the endoplasmic reticulum (ER) and the mitochondria in these cells.
Petersen
Ole H
OH
MRC Secretory Control Research Group, The Physiological Laboratory, University of Liverpool, Liverpool L69 3BX, UK. o.h.petersen@liv.ac.uk
D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism* / Q000502:physiology; D003594:Cytoplasmic Granules / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005088:Exocrine Glands / Q000378:metabolism*; D005089:Exocytosis; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism
D015220:Calcium Channels; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium