title: A cation-retaining layer in the alveolar-capillary membrane.
abstract: The ultrastructural cytochemistry of the alveolar-capillary "membrane" has been investigated. Dialyzed iron and high iron diamine staining demonstrated a layer containing sulfated mucosubstance at the basal surface of the membranous pneumocytes. In the same layer, fixation with an osmium tetroxide-potassium pyroantimonate solution yielded abundant fine precipitates which were abolished by inclusion of ehtylene glycol bis-N,N'-tetraacetic acid (EGTA) in the fixative. This cation-retaining layer could be interpreted as providing a mechanism for retarding cation transport from the basement membrane to the alveolar space. High iron diamine staining also demonstrated a layer of sulfated mucosubstance on the microvilli of the granular pneumocytes. This layer corresponded with a sialidase-resistant, dialyzed iron-reactive stratum which overlaid the sialomucin-rich cell coat.
mesh_terms: D000818:Animals; D000965:Antimony; D001485:Basement Membrane / Q000648:ultrastructure; D002196:Capillaries / Q000648:ultrastructure*; D002241:Carbohydrates; D002414:Cations, Monovalent; D002462:Cell Membrane / Q000648:ultrastructure; D004727:Endothelium / Q000648:ultrastructure; D007501:Iron; D009439:Neuraminidase; D009992:Osmium; D011650:Pulmonary Alveoli / Q000098:blood supply / Q000648:ultrastructure*; D051381:Rats; D013194:Staining and Labeling
chemical_list: D002241:Carbohydrates; D002414:Cations, Monovalent; D009992:Osmium; D000965:Antimony; D007501:Iron; D009439:Neuraminidase