Baseline assessments Seven days prior to this visit, subjects will adhere to a `normal-salt' (9 - 12 grams or 150 - 200 mmol per day) and protein (1.5 - 2.0 g/kg per day) diets, in order to minimize variation in renal physiology due to salt and protein intake. Participants will abstain from alcohol (24 hours), caffeine (12 hours) and nicotine (12 hours) and heavy exercise prior to and during visits 2. One day prior to the testing day, subjects will collect 24-hour urine.