The main characteristic of polycystic kidney disease (PKD) is the development of multiple fluid filled renal cysts. The discovery of mislocated Na, K-ATPase in the apical membrane of cyst lining epithelia alluded to a reversal of polarity as a possible explanation for the fluid secretion. The topic of apical Na, K-ATPase in cysts remains controversial with some investigators finding conventional localization in cysts. Thus, we investigated localization of the Na, K-ATPase and assessed the apical-basolateral polarization of cyst lining epithelia by means of immunohistochemistry on tissue from six anonymous PKD patients undergoing nephrectomy. The Na, K-ATPase α1 subunit was conventionally situated in the basolateral membrane of all immunoreactive cysts. Proteins of the Crumbs and partitioning defective (Par) complexes were localized to the apical membrane domain in cyst epithelial cells. The apical t-SNARE protein Syntaxin-3 also immunolocalized to the apical domain of cyst lining epithelial cells. Proteins of the basolateral Scribble complex immunolocalized to the basolateral domain of cysts. Furthermore, we confirmed that cysts can originate from virtually any tubular segment with preserved polarity. In conclusion, we find no evidence of a reversal in apical-basolateral polarity in cyst lining epithelia in polycystic kidney disease. This study was supported by Aarhus University Research Foundation(AUFF) AU-Ideas, and the Danish Council for Independent Research—MedicalSciences. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.