Mediates the exchange of one Ca(2+) ion against three to four Na(+) ions across the cell membrane, and thereby contributes to the regulation of cytoplasmic Ca(2+) levels and Ca(2+)-dependent cellular processes (PubMed:7986817). Contributes to Ca(2+) transport during excitation-contraction coupling in muscle. In a first phase, voltage-gated channels mediate the rapid increase of cytoplasmic Ca(2+) levels due to release of Ca(2+) stores from the endoplasmic reticulum. SLC8A1 mediates the export of Ca(2+) from the cell during the next phase, so that cytoplasmic Ca(2+) levels rapidly return to baseline. Required for normal embryonic heart development and the onset of heart contractions (By similarity). Ca(2+)(in) + 3 Na(+)(out) = Ca(2+)(out) + 3 Na(+)(in) Activated by micromolar levels of Ca(2+). The cytoplasmic Calx-beta domains bind the regulatory Ca(2+). The first Calx-beta domain can bind up to four Ca(2+) ions. The second domain can bind another two Ca(2+) ions that are essential for calcium-regulated ion exchange. Belongs to the Ca(2+):cation antiporter (CaCA) (TC 2.A.19) family. SLC8 subfamily.