Variables measured: Total body water will be determined using bioelectrical impedance from Valhalla Scientific body comp scale®. Blood pressure monitors will be provided to each participant for measurement and record their own blood pressure twice daily for the duration of the study. In addition, at the end of each of the two sodium loading phases, trained personnel will measure BP three time using standard procedures, following an 8 hour fast and a 10 minute rest period at the clinic. Laboratory measurements. Blood and urine analysis will be performed at the start and end of each salt loading phase at the Advanced Research and Diagnostic Laboratory (ARDL). NT-proBNP will be measured using the Roche-Elecsys proBNP® (Roche Diagnostics, Indianapolis, IN). This method has a range of values that extends from 1 - 25000 pg/mL and the intra-assay precision is below 4% and the CV and interassay precision below 5% 21. Plasma BNP will be measured on a Siemens Advia Centaur instrument using a chemiluminescent immunoassay which has a minimal detection limit of 1.9 pg/mL and a CV of 3.4%. cGMP will be measured using a competitive enzyme immunoassay by Bio-Techne (Minneapolis, MN) intra essay CV is 7%. NT-proBNP will be measured using the Roche-Elecsys proBNP® (Roche Diagnostics, Indianapolis, IN). This method has a range of values that extends from 1 - 25000 pg/mL and the intra-assay precision is below 4% CV and inter-assay precision below 5% 21.