The molecular basis for active ion transport in many secretory glands such as the prostate has not yet been well characterized. The rat nongastric H,K-ATPase is known to be expressed at high levels in apical membranes of distal colon surface cells and thus is often referred to as "colonic" H,K-ATPase. Here we show that the ATPase is expressed in the rodent prostate complex in a lobe-specific manner. Results of RT-PCR and western blotting indicate that the rat nongastric H,K-ATPase -subunit (ng) mRNA and protein are present in the coagulating gland (anterior prostate), lateral and dorsal prostate and are absent from the ventral lobe, while Na,K-ATPase -subunit is present in all lobes. RT-PCR analysis shows that 4 and 3 isoforms of the Na,K-ATPase (4, 3) and the gastric H,K-ATPase -subunit (g) are not present in significant amounts in all lobes of the prostate. Relatively low levels of 2 isoform of Na,K-ATPase (2) were found in lateral, dorsal, and anterior lobes. The expression of ng protein is anteriodorsolateral with the highest level in the coagulating gland, somewhat lower in the dorsal lobe, and even lower in the lateral lobe. The Na,K-ATPase protein abundance has the reverse order with the expression in the ventral lobe being higher than in the coagulating gland. The abundance of the ng protein in membranes from the coagulating gland is higher than in the distal colon membranes. Immunohistochemistry shows that in rat and mouse coagulating gland epithelium the ng protein has an apical polarization while Na,K-ATPase 1-subunit is localized in basolateral membranes. The presence of the nongastric H,K-ATPase in the apical membranes of the rodent prostate lobes may indicate that this enzyme is involved in regulation of potassium concentration in secretions of these glands.