Immunolocalization of 15-kDa membrane proteins in the kidneys of normal and acidotic rats.
Proteins with apparent molecular masses between 15 kDa and 17 kDa were enriched from rat renal brush-border membranes by preparative gel electrophoresis and used for immunization of rabbits. The serum of one of the rabbits reacted in Western blots of separated renal brush-border proteins with a single 15-kDa band. A comparably strong reaction is seen with a 15-kDa band of renal endosomal proteins. Basolateral membranes show a much weaker reaction. In light- and electron-microscopic studies the serum stains brush-border membranes and endosomes in rat proximal tubule cells, but not mitochondria and basolateral membranes. In cortical collecting ducts, principal cells are not stained with the antiserum. alpha-type (H(+)-secreting) intercalated cells bind the antibodies at apical tubulovesicles. The luminal membrane is scarcely labelled. Conversely, beta-type (HCO3(-)-secreting) intercalated cells exhibit antibody binding to their basolateral membrane. Thus, the antiserum detects 15-kDa proteins differently sorted in alpha- and beta-intercalated cells. After induction of an acute (6 h) metabolic acidosis, the antibody-binding pattern changes only in intercalated cells, type alpha, and occurs at the markedly enlarged luminal plasma membrane. The amount of alpha-type intercalated cells with enlarged luminal membrane ("secreting cell") increases at the expense of alpha cells with apical tubulovesicles ("resting cell"). Taken together, the antiserum detects 15-kDa proteins, the localization and adaptive changes to metabolic acidosis of which are similar to H(+)-ATPases. The functional role of the 15-kDa proteins needs to be established in further studies.
Jehmlich
K
K
Max-Planck-Institut für Biophysik, Frankfurt am Main, Federal Republic of Germany.
Sablotni
J
J
Heitmann
K
K
Burckhardt
G
G
Haase
W
W
D000138:Acidosis / Q000378:metabolism*; D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D007150:Immunohistochemistry / Q000379:methods; D007668:Kidney / Q000378:metabolism* / Q000648:ultrastructure; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008854:Microscopy, Electron; D008871:Microvilli / Q000378:metabolism; D008970:Molecular Weight; D051381:Rats; D012016:Reference Values; D013194:Staining and Labeling
D008565:Membrane Proteins