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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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Setup to measure water balance in mice of different ages.A) Diagram showing experimental design. Mice were placed in metabolic cages and subjected to 4 consecutive periods (3 days each) of progressively reduced water content (from 56% to 33%) of their gel food. B) Consumption of food and water, calculated based on the water content of the gel food and the amount of gel food consumed each day (median and IQR, n = 3–4, # P<0.05 relative to 56% water in gel food). 3 and 18 month old mice eat similar amount of food at all water availability that does not change with decreasing water content. 27 month old mice decrease amount of food eaten when water content decreases to 33%.
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pone-0020691-g001: Setup to measure water balance in mice of different ages.A) Diagram showing experimental design. Mice were placed in metabolic cages and subjected to 4 consecutive periods (3 days each) of progressively reduced water content (from 56% to 33%) of their gel food. B) Consumption of food and water, calculated based on the water content of the gel food and the amount of gel food consumed each day (median and IQR, n = 3–4, # P<0.05 relative to 56% water in gel food). 3 and 18 month old mice eat similar amount of food at all water availability that does not change with decreasing water content. 27 month old mice decrease amount of food eaten when water content decreases to 33%.

Mentions: Figure 1B shows the daily consumption of food and water, combined in a gel. Reducing the water content of the gel food decreases water intake, but intake of food remains constant. Although the older mice are larger, the amount of food that they consume is similar to that consumed by the younger mice over the course of the experiment. The exception is that 27 month old mice consumed less during the last period when water content of the gel food was decreased to 33%. Those mice were very dehydrated by then (see below). Since water intake was similar for the mice of different ages, any differences in hydration were due to differences in water loss.


Increased insensible water loss contributes to aging related dehydration.

Dmitrieva NI, Burg MB - PLoS ONE (2011)

Setup to measure water balance in mice of different ages.A) Diagram showing experimental design. Mice were placed in metabolic cages and subjected to 4 consecutive periods (3 days each) of progressively reduced water content (from 56% to 33%) of their gel food. B) Consumption of food and water, calculated based on the water content of the gel food and the amount of gel food consumed each day (median and IQR, n = 3–4, # P<0.05 relative to 56% water in gel food). 3 and 18 month old mice eat similar amount of food at all water availability that does not change with decreasing water content. 27 month old mice decrease amount of food eaten when water content decreases to 33%.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3105115&req=5

pone-0020691-g001: Setup to measure water balance in mice of different ages.A) Diagram showing experimental design. Mice were placed in metabolic cages and subjected to 4 consecutive periods (3 days each) of progressively reduced water content (from 56% to 33%) of their gel food. B) Consumption of food and water, calculated based on the water content of the gel food and the amount of gel food consumed each day (median and IQR, n = 3–4, # P<0.05 relative to 56% water in gel food). 3 and 18 month old mice eat similar amount of food at all water availability that does not change with decreasing water content. 27 month old mice decrease amount of food eaten when water content decreases to 33%.
Mentions: Figure 1B shows the daily consumption of food and water, combined in a gel. Reducing the water content of the gel food decreases water intake, but intake of food remains constant. Although the older mice are larger, the amount of food that they consume is similar to that consumed by the younger mice over the course of the experiment. The exception is that 27 month old mice consumed less during the last period when water content of the gel food was decreased to 33%. Those mice were very dehydrated by then (see below). Since water intake was similar for the mice of different ages, any differences in hydration were due to differences in water loss.

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