The osmopressor response to water drinking

Abstract

Water drinking elicits profound pressor responses in patients with impaired baroreflex function and in sinoaortic-denervated mice. Healthy subjects show more subtle changes in heart rate and blood pressure with water drinking. The water-induced pressor response appears to be mediated through sympathetic nervous system activation at the spinal level. Indeed, water drinking raises resting energy expenditure in normal weight and obese subjects. The stimulus setting off the response is hypoosmolarity rather than water temperature or gastrointestinal stretch. Studies in mice suggest that this osmopressor response may involve transient receptor potential vanniloid 4 (Trpv4) receptors. However, the (nerve) cell population serving as peripheral osmosensors and the exact transduction mechanisms are still unknown. The osmopressor response can be exploited in the treatment of orthostatic and postprandial hypotension in patients with severe autonomic failure. Furthermore, the osmopressor response acutely improves orthostatic tolerance in healthy subjects and in patients with neurally mediated syncope. The phenomenon should be recognized as an important confounder in cardiovascular and metabolic studies.

Ingestão De Água No Sistema Nervoso Autônomo: Uma Revisão Sistemática E Meta-Análise

“…Todavia, a teoria da osmolalidade vem sendo alvo de grandes estudos e mostram que a IA é capaz de estimular o receptor Trpv4, localizados no fígado e na circulação portal. Porém, toda a população dos receptores e os mecanismos de transdução ainda não estão bem esclarecidos, sendo aqueles sensíveis à queda de osmolalidade, no qual realizam um aumento reflexo da atividade simpática nervosa muscular, através do estímulo na atividade adrenérgica pós-ganglionar 21 .…”

“…Já é demonstrado que o consumo de água tem se tornado um fator profilático e terapêutico para pacientes que sofrem de hipotensão ortostática [14][15][16] , e tendo em vista que o tratamento medicamentoso é dispendioso e o efeito bastante questionado 17 , percebeu-se a necessidade de encontrar os reais estímulos fisiológicos causados pela IA que induzem as respostas autonômicas, na qual duas vertentes vêm sendo alvo de maiores estudos para esclarecer tal fenômeno como a distensão gástrica 18,19 e a osmolalidade 20, 21 .…”

Acute effect of oral water intake during exercise on post-exercise hypotension

“…11,30 Oral water intake also has effects on BP and HR in normal subjects, although the actions are more subtle. 13,31 The water-induced pressor response appears to be mediated through sympathetic nervous activation. 32 However, this increase in BP after fluid ingestion is not obtained when the same volume of 5% dextrose in water is administered by venous infusion.…”

“…32 The pressor response after water drinking at rest is likely to result from hypoosmolarity rather than gastrointestinal stretch or water temperature, because the maximal response was usually observed after B40 min. 13 The local changes in osmolality through water drinking may elicit a powerful pressor response via sympathetic nervous system activation. Studies in mice suggest that this osmopressor response may involve activation of transient receptor potential vanilloid 4 receptors, which may be located on putative peripheral osmoreceptors in the portal vein and liver.…”

“…[10][11][12] Also, oral water intake has an acute effect on BP even in normal subjects, although the effects are more subtle. 11,13 Although the exact mechanism that causes this pressor response has not been precisely elucidated, it is likely to involve vasoconstriction via water-induced sympathetic activation. 12,14 The increase in BP by drinking water is associated with an increase in plasma norepinephrine levels and sympathetic nerve discharge, 15 and a consequent increase in vascular resistance in the periphery.…”