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Body fluid balance in dehydrated healthy older men: thirst and renal osmoregulation.
J Appl Physiol (1985). 1994 Apr; 76(4):1615-23.JA

Abstract

We examined osmotic control of thirst and free water clearance in healthy older (65+, n = 10) and younger (Y, n = 6) subjects during a 3-h rehydration period after an approximately 2.4% decrease in body weight. Plasma volume (PV), plasma osmolality (Posm), renal function, and thirst were measured before and after dehydration and during rehydration. In 65+, baseline PV was lower (43.1 +/- 1.6 vs. 48.1 +/- 2.5 ml/kg), Posm was higher (287 +/- 1 vs. 281 +/- 2 mosmol/kgH2O), and perceived thirst was lower than in Y. During dehydration, the osmotic threshold for increased thirst was shifted to a higher Posm in 65+. Total fluid intake was greater in Y than in 65+ (16.6 +/- 4.1 vs. 8.9 +/- 2.0 ml/kg); however, the relation between thirst and the rate of fluid intake was identical. Thus the blunted rehydration in 65+ is related to a lower overall sensation of thirst. The stimulus-response characteristics of osmotic control of free water clearance was similar in 65+ and Y; however, 65+ operated around a higher Posm and on a less-steep portion of the stimulus-response curve. These data support the hypothesis that the hyperosmotic hypovolemic state of healthy older individuals is not a result of a simple water deficit but represents a shift in the operating point for control of body fluid volume and composition.

Authors+Show Affiliations

John B. Pierce Laboratory, Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven 06519.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

8045840

Citation

Mack, G W., et al. "Body Fluid Balance in Dehydrated Healthy Older Men: Thirst and Renal Osmoregulation." Journal of Applied Physiology (Bethesda, Md. : 1985), vol. 76, no. 4, 1994, pp. 1615-23.
Mack GW, Weseman CA, Langhans GW, et al. Body fluid balance in dehydrated healthy older men: thirst and renal osmoregulation. J Appl Physiol. 1994;76(4):1615-23.
Mack, G. W., Weseman, C. A., Langhans, G. W., Scherzer, H., Gillen, C. M., & Nadel, E. R. (1994). Body fluid balance in dehydrated healthy older men: thirst and renal osmoregulation. Journal of Applied Physiology (Bethesda, Md. : 1985), 76(4), 1615-23.
Mack GW, et al. Body Fluid Balance in Dehydrated Healthy Older Men: Thirst and Renal Osmoregulation. J Appl Physiol. 1994;76(4):1615-23. PubMed PMID: 8045840.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Body fluid balance in dehydrated healthy older men: thirst and renal osmoregulation. AU - Mack,G W, AU - Weseman,C A, AU - Langhans,G W, AU - Scherzer,H, AU - Gillen,C M, AU - Nadel,E R, PY - 1994/4/1/pubmed PY - 1994/4/1/medline PY - 1994/4/1/entrez SP - 1615 EP - 23 JF - Journal of applied physiology (Bethesda, Md. : 1985) JO - J. Appl. Physiol. VL - 76 IS - 4 N2 - We examined osmotic control of thirst and free water clearance in healthy older (65+, n = 10) and younger (Y, n = 6) subjects during a 3-h rehydration period after an approximately 2.4% decrease in body weight. Plasma volume (PV), plasma osmolality (Posm), renal function, and thirst were measured before and after dehydration and during rehydration. In 65+, baseline PV was lower (43.1 +/- 1.6 vs. 48.1 +/- 2.5 ml/kg), Posm was higher (287 +/- 1 vs. 281 +/- 2 mosmol/kgH2O), and perceived thirst was lower than in Y. During dehydration, the osmotic threshold for increased thirst was shifted to a higher Posm in 65+. Total fluid intake was greater in Y than in 65+ (16.6 +/- 4.1 vs. 8.9 +/- 2.0 ml/kg); however, the relation between thirst and the rate of fluid intake was identical. Thus the blunted rehydration in 65+ is related to a lower overall sensation of thirst. The stimulus-response characteristics of osmotic control of free water clearance was similar in 65+ and Y; however, 65+ operated around a higher Posm and on a less-steep portion of the stimulus-response curve. These data support the hypothesis that the hyperosmotic hypovolemic state of healthy older individuals is not a result of a simple water deficit but represents a shift in the operating point for control of body fluid volume and composition. SN - 8750-7587 UR - https://www.unboundmedicine.com/medline/citation/8045840/Body_fluid_balance_in_dehydrated_healthy_older_men:_thirst_and_renal_osmoregulation_ L2 - http://journals.physiology.org/doi/full/10.1152/jappl.1994.76.4.1615?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -