Ultrastructural Localization of the Ammonia Transporter Protein, RhCG, in Rat Kidney Collecting Duct / 대한해부학회지

ABSTRACT

Ammonia excretion in the renal collecting duct is critical in the regulation of the acid-base homeostasis. A novel family of ammonium transporter protein, Rh C Glycoprotein (RhCG) was recently identified in the mouse and rat kidney collecting duct. The purpose of this study was to examine the ultrastructural localization of RhCG in the collecting duct. Rat kidneys were processed for light and electron microscope immunocytochemistry using anti-RhCG rabbit polyclonal antibody. Strong RhCG immunolabeling was observed in the apical domain of AE1-positive type A intercalated cells in the collecting duct. Transmission electron microscopy revealed that a high level of RhCG was expressed in the apical plasma membrane and in subapical vesicles of type A intercalated cell. Interestingly, type A cells also expressed weak immunolabel in the basolateral plasma membrane. Type B cells had weak apical plasma membrane and subapical vesicle immunolabel, and very weak basolateral plasma membrane immunolabel. Principal cells had very weak apical plasma membrane immunolabel without detectable subapical or basolateral immunolabel These results demonstrate that RhCG is mainly expressed in the apical plasma membrane and in subapical vesicles of acid-secreting type A cells and may mediate ammonia excretion in the collecting duct.