Antibodies that are agonists of sodium pump (Na+/K+ ATPase; NKA) activity are provided. In particular, antibodies that specifically bind epitopes on the beta-1 (β1) subunit of NKA are disclosed. These antibodies have the ability to increase the activity of the catalytic alpha subunit of NKA upon β1 subunit binding. Due to their activity, the antibodies also have the ability to trigger a positive inotropic effect in cardiac tissues (i.e., increase cardiac contraction). The present invention thus includes, but is not limited to, NKA β1 subunit peptide epitopes, antibodies that specifically bind the epitopes, methods of increasing NKA activity and cardiac contraction through administration of the peptide vaccines or the antibodies, and methods of treating and/or preventing heart disease through administration of the peptides or the antibodies.