Blood samples will be obtained and an oral glucose tolerance test (OGTT) performed. Baseline exhaled nitric oxide (NO) and pulmonary blood flow will be measured in collaboration with Dr Bruce Thompson from the Alfred Respiratory Department. Sodium nitroprusside (SNP) is a known NO donor and will be used as a positive control. Following baseline measurements participants will receive an intravenous (forearm vein) infusion of SNP (titrated from 0.3ug/kg/min to a maximum of 3 ug/kg/min over 30 minutes). Blood pressure will be monitored throughout using an automated sphygmomanometer. Post infusion exhaled NO and pulmonary blood flow will be measured.