Structure-function relationships in H+-secreting epithelia.
Stimulation or inhibition of H+ secretion has been associated with characteristic ultrastructural changes in various epithelial cells, including the parietal cell of the gastric mucosa, the carbonic anhydrase (CA)-rich cell of the turtle urinary bladder, and the intercalated (I) cell of the mammalian collecting duct. An electroneutral potassium-activated H+-ATPase is responsible for H+ secretion in the stomach, whereas acidification in the turtle bladder and the mammalian collecting duct is mediated by an electrogenic H+-translocating ATPase. Despite these differences, the parietal cell, the CA-rich cell, and the I cell have several morphological features in common. They are rich in mitochondria, contain numerous tubulovesicular membrane structures in the apical region of the cell, and possess a variable number of microprojections on the luminal surface. After stimulation of H+ secretion there is a significant increase in the surface area of the apical membrane concomitant with a decrease in the tubulovesicular membrane compartment in these cells, as revealed by morphometric analysis. These findings suggest that membrane (possibly containing an H+ pump) is being transferred from the tubulovesicular compartment to the apical plasma membrane on stimulation of H+ secretion. A hypothesis of membrane recycling is proposed to account for the observed morphological changes.
K M
KM
Madsen
C C
CC
Tisher
D000663:Amphibians; D000818:Animals; D002256:Carbonic Anhydrases / Q000502:physiology; D004848:Epithelium / Q000378:metabolism / Q000648:ultrastructure; D007473:Ion Channels / Q000378:metabolism / Q000648:ultrastructure*; D007685:Kidney Tubules, Collecting / Q000378:metabolism / Q000648:ultrastructure; D008854:Microscopy, Electron; D010295:Parietal Cells, Gastric / Q000378:metabolism / Q000648:ultrastructure; D011522:Protons; D011817:Rabbits; D051381:Rats; D014426:Turtles; D001743:Urinary Bladder / Q000378:metabolism / Q000648:ultrastructure
D007473:Ion Channels; D011522:Protons; D002256:Carbonic Anhydrases