The presence of a vacuolar-type ATPase in Malpighian tubules of the antFormica polyctenawas investigated immunocytochemically, using antibodies to vacuolar ATPases ofManduca sextamidgut and bovine kidney. Specific labelling was observed at the brush border of the epithelium extending along the entire length of the tubules. These findings agree with the current view that a vacuolar ATPase is situated at the apical membrane of Malpighian tubule cells and other insect epithelial cells, being the energizing element of an electrogenic potassium pump. When antibodies were tested on tubules in different secretion conditions prior to fixation, no differences were observed in the distribution of the vacuolar ATPase.
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