1993 Fiscal Year Final Research Report Summary
Extracellular rather than intracellular pathway plays an important role in attenuating thirst and drinking desirability during head-out immersion in hypohydrated men.
| Project/Area Number |
03454138
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
環境生理学(含体力医学･栄養生理学)
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| Research Institution | University of Occupational and Environmental Health |
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Principal Investigator |
SHIRAKI Keizo University of Occupational and Environmental Health, School of Medicine Physiology Professor, 医学部, 教授 (00035453)
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| Project Period (FY) |
1991 – 1993
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| Keywords | Thirst / Plasma volume / Plasma osmolality / Plasma arginine vasopressin / Cardiopulmonary baroreceptors / Atrial natriuretic peptides / 尿量 / 心房性ナトリウム利尿ペプチド |
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| Research Abstract |
The purpose of this study was to investigate the mechanisms underlying a reduction of thirst sensation during head-out water immersion (HOI) in hypohydrated subjects. Eight males (19-25 yr) were subjected to thermoneutral HOI (water temperature ; 34.5ﾟC) and thermoneutral air (room temperature ; 28ﾟC) under two different conditions, euhydrated (Eu-H_2O and Eu-air) and hypohydrated (Hypo-H_2O, 3.8% weight loss after exercise in heat, Posm = +10 mosmol/kg and Hypo-air). Subjects were not allowed to drink throughout experimental periods. Thirst sensation on a visual analog scale with Hypo-H_2O was decreased (P<0.05) in 10 min of HOI.A significant attenuation of diuresis and a sustained increase in plasma volume occurred throughout HOI with Hypo-H_2O.In Eu-H_2O, however, a transient plasma expansion was observed early during HOI, while a remarkable diuresis was observed throughout HOI.There was a prompt and sustained increase (P<0.05) in the plasma level of atrial natriuretic peptides and a sustained decrease (P<0.05) in the plasma renin activity during HOI in both Eu-H_2O and Hypo-H_2O.Plasma arginine vasopressin decreased (P<0.05) during HOI in Hypo-H_2O but not in Eu-H_2O.The increment of stroke volume was greater (P<0.05) with Hypo-H_2O during HOI.Therefore, a greater increase (P<0.05) in stroke volume during HOI may suggest the greater stimulation of the mechanoreceptors with Hypo-H_2O.Plasma osmolality remained elevated in the presence of an attenuated thirst during HOI.Thus, the present results may support the hypothesis that the extracellular pathways may play an important role in reducing thirst sensation during HOI in hypohydrated subjects.
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