On arrival at the Clinical Research Centre on the study day, a brief medical enquiry and examination will confirm the ongoing suitability of the subject for the study. An intravenous cannula will be inserted into the antecubital fossa of each arm. We have developed a basic protocol described fully in our previous studies that allows us to measure systemic haemodynamics by the well validated technique of bioimpedance and renal function by standard para-aminohippurate (PAH; renal blood flow) and inulin (glomerular filtration rate) clearance studies.