Involved in actively transporting phosphate into cells via Na(+) cotransport. 3 Na(+)(out) + phosphate(out) = 3 Na(+)(in) + phosphate(in) Localized at the brush border membranes of enterocytes. Highly expressed in the lung, in type II alveolar cells. Moderately expressed in kidney followed by small intestine. Appears on embryonic day 16.5 and is expressed thereafter. Up-regulated by estrogen. Belongs to the SLC34A transporter family.