Fig. 2. Immunolocalization of P-type Na⁺/K⁺-ATPase (red) and V-type H⁺-ATPase (blue) in the fourth instar larval A. aegypti Malpighian tubules, rectum and anal papillae. In the distal Malpighian tubule (MT) whole mounts (A,D,E) P-type Na⁺/K⁺-ATPase was highly expressed in the stellate cells (SC; D, white arrow), whereas V-type H⁺-ATPase was expressed only in the principal cells (PC; E, white arrow). V-type H⁺-ATPase was expressed in the distal principal cell on the apical membrane and cytoplasmically as evident in paraffin sections (H). In the proximal Malpighian tubules (B,C), there were no stellate cells and the principal cells had P-type Na⁺/K⁺-ATPase and V-type H⁺-ATPase on the basal and apical membranes, respectively, as seen in the paraffin sections (G). The rectal epithelium expressed high levels of P-type Na⁺/K⁺-ATPase (F) on the basal membrane (I, white arrow) whereas the anterior hindgut (AHG) showed little expression of either ATPase (F). P-type Na⁺/K⁺-ATPase and V-type H⁺-ATPase were localized to the basal and apical aspects respectively of the anal papillae (J,K). A,F,G,I-K are overlays of Cy3 and Cy5 signal and in B-E, H, the signals have been separated. Scale bars, 100 µm (A,F), 50 µm (B-E,I,J), 10 µm (G,H,K).