The capability of epithelial cells in caprine mammary glands to absorb electrolytes across the apical membranes is poorly investigated. This study was performed to examine the capacity of sodium-dependent phosphate transport across the apical membranes and to identify sodium-phosphate transporters on molecular level. Apical membranes delivered physiologically from epithelial cells were used for radioactive vesicle uptake studies. An inside-directed sodium-dependent phosphate transport across the apical membrane was detected with a strong sodium dependency. Phosphonoformic acid inhibited the transport process in a dose-dependent manner. This phosphate transport seemed to be based on a sodium phosphate cotransporter type IIb (SLC34A2). The respective protein could be detected in the isolated apical membranes specifically by western analysis. This was confirmed by localising NaPi IIb immunhistochemically in the apical membranes of epithelial cells. The physiological meaning of phosphate reabsorption in epithelial cells of caprine mammary glands remains unclear. Possibly, this transport mechanism supports the electrolyte maintenance of epithelial cells during lactation and -with more significance - during regeneration within the involution.