The molecular basis of active ion transport in secretory glands such as the prostate is not well characterized. Rat nongastric H-K-ATPase is expressed at high levels in distal colon surface cell apical membranes and thus is referred to as "colonic." Here we show that the ATPase is expressed in rodent prostate complex in a lobe-specific manner. RT-PCR and Western blot analyses indicate that rat nongastric H-K-ATPase -subunit (_ng) mRNA and protein are present in coagulating gland (anterior prostate) and lateral and dorsal prostate and absent from ventral lobe, whereas Na-K-ATPase -subunit is present in all lobes. RT-PCR analysis shows that Na-K-ATPase ₄ and ₃ and gastric H-K-ATPase -subunit are not present in significant amounts in all prostate lobes. Relatively low levels of Na-K-ATPase ₂ were found in lateral, dorsal, and anterior lobes. _ng protein expression is anteriodorsolateral: highest in coagulating gland, somewhat lower in dorsal lobe, and even lower in lateral lobe. Na-K-ATPase protein abundance has the reverse order: expression in ventral lobe is higher than in coagulating gland. _ng protein abundance is higher in coagulating gland than distal colon membranes. Immunohistochemistry shows that in rat and mouse coagulating gland epithelium _ng protein has an apical polarization and Na-K-ATPase ₁ is localized in basolateral membranes. The presence of nongastric H-K-ATPase in rodent prostate apical membranes may indicate its involvement in potassium concentration regulation in secretions of these glands.