Water Ingestion Reduced Exhaled Nitric Oxide in the Course of the Osmopressor Response

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Water ingestion induces a robust increase in blood pressure (BP) and vascular resistance in patients with an impaired efferent baroreflex. The mild pressor response was also present in elderly healthy subjects; however, there was no change in arterial blood pressure and notably no change, or even a slight reduction in heart rate in young healthy subjects. Nitric oxide (NO) has emerged as a major regulator mechanism of the cardiovascular system and the stressful situation has been linked to a reduction in serum NO.Thus we hypothesized that the exhaled nitric oxide(eNO) might be feasible to be a biomarker that can aid in the research of the osmopressor responses. The purpose of the present study was to examine whether the non-invasive monitor of eNO could reflect the osmopressor response after water ingestion. In a randomized, controlled, crossover fashion, 34 young healthy subjects (age, 22–35 years) ingested either 500 or 50 mL of water. Heart rate, BP, cardiac index, and total peripheral vascular resistance were measured using a Finometer hemodynamic monitor. eNO was determined by a chemiluminescence analyser before and after subjects ingested either 500 or 50 mL of water. Blood sampling for plasma osmolality was performed at 5 min before and at 25 min after either the water ingestion or control session. At 25 min after the ingestion of 500 mL of water, total peripheral resistance increased significantly, and plasma osmolality decreased. eNO decreased significantly at 25 min after ingestion of 500 mL water. This study suggests that water ingestion induced decrease of the eNO might be used as a novel biological marker in the course of the osmopressor response.