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Immunocytochemical localization of Na,K-ATPase in intercalated cells along rat nephron

IMMUNOCYTOCHEMICAL LOCALIZATION OF Na+/K+-ATPase IN INTERCALATED CELLS ALONG RAT NEPHRON Ivan Sabolic, Sylvie Breton and Dennis Brown, IMI, Zagreb, Croatia and MGH, Boston, USA Na+/K+-ATPase plays a fundamental role in physiology of various mammalian cells. In kidney, previous immunocytochemical investigations have localized this protein to the basolateral membrane in various tubule segments. However, intercalated cells (IC) of the collecting duct (CD) in rat remained unlabeled with the anti-Na+/K+-ATPase antibodies, thus leaving the question regarding the presence of this protein in IC open. By immunofluorescence cytochemistry we re-examined the presence of this antigen in IC along the rat nephron using a mono-clonal anti-Na+/K+-ATPase a-subunit antibody on detergent-treated cryostat sections of the fixed kidney tissue. Various types of IC along the nephron were discerned by the distinctive staining with polyclonal and monoclonal antibodies to 31 kDa vacuolar H+-ATPase subunit, whereas principal cells (PC) were distinguished by their basolateral labeling with a polyclonal antibody to water channel aquaporin-4 (AQP-4). In PC, the Na+/K+-ATPase and AQP-4 staining co-localized basolaterally. IC of all types also exhibited basolateral labeling with the anti-Na+/K+-ATPase antibody; the staining was weak in IC of the cortical and outer-medullary CD and strong in IC of the inner-medullary CD. A limited amount of Na+/K+-ATPase in IC along the rat nephron may play a house-keeping role in maintaining normal intracellular concentration of Na+ and K+.

Na;K-ATPase; intercalated cells; kidney tubule; rat

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