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Increased insensible water loss contributes to aging related dehydration.

Dmitrieva NI, Burg MB - PLoS ONE (2011)

Bottom Line: All 3 groups maintain water balance while consuming only the water in gel food containing 56% water.However, both older groups excrete a smaller volume of urine of higher osmolality, indicating greater extra urinary water loss.The greater insensible water loss occurs at an earlier age (18 months) than decreased urine concentrating ability (27 months).

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Kidney and Electrolyte Metabolism, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America. dmitrien@nhlbi.nih.gov

ABSTRACT
Dehydration with aging is attributed to decreased urine concentrating ability and thirst. We further investigated by comparing urine concentration and water balance in 3, 18 and 27 month old mice, consuming equal amounts of water. During water restriction, 3 month old mice concentrate their urine sufficiently to maintain water balance (stable weight). 18 month old mice concentrate their urine as well, but still lose weight (negative water balance). 27 month old mice do not concentrate their urine as well and lose even more weight than the 18 month old mice, indicating a larger negative water balance. Negative water balance in older mice is accompanied by increased vasopressin excretion, providing further evidence of dehydration. All 3 groups maintain water balance while consuming only the water in gel food containing 56% water. However, both older groups excrete a smaller volume of urine of higher osmolality, indicating greater extra urinary water loss. Since their feces also contain less water, the excess water lost by the older mice apparently is through other routes, presumably insensible loss through the respiratory tract and skin. The greater insensible water loss occurs at an earlier age (18 months) than decreased urine concentrating ability (27 months). We propose that insensible water loss through skin and respiration increases with age, making a major contribution to aging related dehydration.

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Analysis of activation of water conservation mechanisms at different levels of water consumption.A) AVP excretion; B) % of water in feces; Note: data are missing for 27 month old mice when gel food contained 33% of water because the mice became constipated; C) Urine volume; D) Urine Osmolality. Data are presented as median and IQR, n = 3–4, * P<0.05 relative to 3 months old; # P<0.05 relative to 56% water in gel food; Mann-Whitney Test (one-tailed).
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pone-0020691-g003: Analysis of activation of water conservation mechanisms at different levels of water consumption.A) AVP excretion; B) % of water in feces; Note: data are missing for 27 month old mice when gel food contained 33% of water because the mice became constipated; C) Urine volume; D) Urine Osmolality. Data are presented as median and IQR, n = 3–4, * P<0.05 relative to 3 months old; # P<0.05 relative to 56% water in gel food; Mann-Whitney Test (one-tailed).

Mentions: Mice of all ages maintained water balance (stable weight) when their gel food contained 56% water (Fig. 2). Consistent with ample hydration, all had low levels of AVP excretion (Fig. 3A). Despite similar water intake (Fig. 1B), however, 18 and 27 month old mice excreted less urine (Fig. 3C) of higher osmolality (Fig. 3D) and had less water in their feces (Fig. 3B) than 3 month old mice. The most plausible explanation for this difference is greater insensible water loss by the older mice. When the water content of their gel food was decreased (Fig. 1B), 3 month old mice adjusted by excreting less urine (Fig. 3C) of higher osmolality (Fig. 3D), and they remained in water balance, as evidenced by stable weight (Fig. 2). 18 month old mice concentrated their urine as much or more than 3 month old mice (Fig. 3C and 3D) and excreted less water in their feces (Fig. 3B), yet they lost weight (Fig. 2), confirming greater insensible water loss than 3 month old mice. 27 month old mice did not concentrate their urine, decrease urine volume (Fig. 3C), or increase their urine osmolality as much as younger mice (Fig. 3D), indicating that their greater dehydration during water restriction (Fig. 2) involved both insensible water loss and loss of water in urine because of decreased concentrating ability. Note that reduced urine volume in 27 month old mice when their gel food contained 33% of water (Fig. 3C) was not due to increased urine concentration (Fig. 3D). We conclude that insensible water loss increases with age in mice and that this occurs at an earlier age (18 months) than decreased urine concentrating ability (27 months).


Increased insensible water loss contributes to aging related dehydration.

Dmitrieva NI, Burg MB - PLoS ONE (2011)

Analysis of activation of water conservation mechanisms at different levels of water consumption.A) AVP excretion; B) % of water in feces; Note: data are missing for 27 month old mice when gel food contained 33% of water because the mice became constipated; C) Urine volume; D) Urine Osmolality. Data are presented as median and IQR, n = 3–4, * P<0.05 relative to 3 months old; # P<0.05 relative to 56% water in gel food; Mann-Whitney Test (one-tailed).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3105115&req=5

pone-0020691-g003: Analysis of activation of water conservation mechanisms at different levels of water consumption.A) AVP excretion; B) % of water in feces; Note: data are missing for 27 month old mice when gel food contained 33% of water because the mice became constipated; C) Urine volume; D) Urine Osmolality. Data are presented as median and IQR, n = 3–4, * P<0.05 relative to 3 months old; # P<0.05 relative to 56% water in gel food; Mann-Whitney Test (one-tailed).
Mentions: Mice of all ages maintained water balance (stable weight) when their gel food contained 56% water (Fig. 2). Consistent with ample hydration, all had low levels of AVP excretion (Fig. 3A). Despite similar water intake (Fig. 1B), however, 18 and 27 month old mice excreted less urine (Fig. 3C) of higher osmolality (Fig. 3D) and had less water in their feces (Fig. 3B) than 3 month old mice. The most plausible explanation for this difference is greater insensible water loss by the older mice. When the water content of their gel food was decreased (Fig. 1B), 3 month old mice adjusted by excreting less urine (Fig. 3C) of higher osmolality (Fig. 3D), and they remained in water balance, as evidenced by stable weight (Fig. 2). 18 month old mice concentrated their urine as much or more than 3 month old mice (Fig. 3C and 3D) and excreted less water in their feces (Fig. 3B), yet they lost weight (Fig. 2), confirming greater insensible water loss than 3 month old mice. 27 month old mice did not concentrate their urine, decrease urine volume (Fig. 3C), or increase their urine osmolality as much as younger mice (Fig. 3D), indicating that their greater dehydration during water restriction (Fig. 2) involved both insensible water loss and loss of water in urine because of decreased concentrating ability. Note that reduced urine volume in 27 month old mice when their gel food contained 33% of water (Fig. 3C) was not due to increased urine concentration (Fig. 3D). We conclude that insensible water loss increases with age in mice and that this occurs at an earlier age (18 months) than decreased urine concentrating ability (27 months).

Bottom Line: All 3 groups maintain water balance while consuming only the water in gel food containing 56% water.However, both older groups excrete a smaller volume of urine of higher osmolality, indicating greater extra urinary water loss.The greater insensible water loss occurs at an earlier age (18 months) than decreased urine concentrating ability (27 months).

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Kidney and Electrolyte Metabolism, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America. dmitrien@nhlbi.nih.gov

ABSTRACT
Dehydration with aging is attributed to decreased urine concentrating ability and thirst. We further investigated by comparing urine concentration and water balance in 3, 18 and 27 month old mice, consuming equal amounts of water. During water restriction, 3 month old mice concentrate their urine sufficiently to maintain water balance (stable weight). 18 month old mice concentrate their urine as well, but still lose weight (negative water balance). 27 month old mice do not concentrate their urine as well and lose even more weight than the 18 month old mice, indicating a larger negative water balance. Negative water balance in older mice is accompanied by increased vasopressin excretion, providing further evidence of dehydration. All 3 groups maintain water balance while consuming only the water in gel food containing 56% water. However, both older groups excrete a smaller volume of urine of higher osmolality, indicating greater extra urinary water loss. Since their feces also contain less water, the excess water lost by the older mice apparently is through other routes, presumably insensible loss through the respiratory tract and skin. The greater insensible water loss occurs at an earlier age (18 months) than decreased urine concentrating ability (27 months). We propose that insensible water loss through skin and respiration increases with age, making a major contribution to aging related dehydration.

Show MeSH
Related in: MedlinePlus