Aging and fluid homeostasis in rats

Rowland, Neil E.; Morien, Annie; Garcea, Mircea; Fregly, Melvin J.

doi:10.1152/ajpregu.1997.273.4.r1441

Cited by 20 publications

(76 citation statements)

References 22 publications

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“…In their study using similar sodium depletion procedures, Rowland et al (30) found that 20-mo-old male SD and F344 rats had reduced sodium intakes compared with their younger (5-mo-old) cohorts. Their old rats repaired through ingestion Ͻ30% of the accrued sodium deficit.…”

Section: Discussionmentioning

confidence: 96%

“…One commonly employed model to stimulate water and sodium ingestion involves administration of a diuretic combined with sodium restriction (30,31,40). Injections of furosemide are given to cause diuresis and natriuresis, and then animals are sodium restricted overnight, having access only to water to drink or to sodium-deficient chow and water.…”

Section: Discussionmentioning

confidence: 99%

“…Investigators variously report that old rats have diminished (14,23,33), increased (4,14,16,22), or unchanged (35,36) daily intakes of water compared with young cohorts. Compared with young rats, old rats reportedly drink equivalent (30) or smaller (33) amounts of water in response to water deprivation and exogenously administered ANG II. Old rats of some strains drink less water than their younger cohorts in response to isoproterenol treatment (30) but drink as much as young rats after osmotic loads (30).…”

mentioning

confidence: 94%

“…Compared with young rats, old rats reportedly drink equivalent (30) or smaller (33) amounts of water in response to water deprivation and exogenously administered ANG II. Old rats of some strains drink less water than their younger cohorts in response to isoproterenol treatment (30) but drink as much as young rats after osmotic loads (30). Old rats have diminished salt appetite responses after sodium depletion and converting enzyme inhibition (28,30).…”

mentioning

confidence: 94%

“…Old rats of some strains drink less water than their younger cohorts in response to isoproterenol treatment (30) but drink as much as young rats after osmotic loads (30). Old rats have diminished salt appetite responses after sodium depletion and converting enzyme inhibition (28,30). There are insufficient data to derive a consensus concerning the conditions under which old rats may express diminished thirst and salt appetite responses.…”

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confidence: 99%

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Thirst and salt appetite responses in young and old Brown Norway rats

Thunhorst

Johnson²

2003

American Journal of Physiology-Regulatory, Integrative and Comp

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Thunhorst, Robert L., and Alan Kim Johnson. Thirst and salt appetite responses in young and old Brown Norway rats. Am J Physiol Regul Integr Comp Physiol 284: R317-R327, 2003. First published October 10, 2002 10.1152/ ajpregu.00368.2002 Norway rats aged 4 mo (young) and 20 mo (old) received a series of experimental challenges to body fluid homeostasis over ϳ3 mo. Water was available for drinking in some tests, and both water and 0.3 M NaCl were available in others. The series included three episodes of extracellular fluid depletion (i.e., furosemide ϩ 20 h of sodium restriction), two tests involving intracellular fluid depletion (i.e., hypertonic saline: 1 or 2 M NaCl at 2 ml/kg body wt sc), one test involving overnight food and fluid restriction, and testing with captopril adulteration of the drinking water (0.1 mg/ml) for several days. Old rats were significantly heavier than young rats throughout testing. Old rats drank less water and 0.3 M NaCl after sodium deprivation than young rats, in terms of absolute and body weightadjusted intakes. Old rats drank only half as much water as young rats in response to subcutaneous hypertonic NaCl when intakes were adjusted for body weight. Old rats drank less 0.3 M NaCl than young rats after overnight food and fluid restriction when intakes were adjusted for body weight. In response to captopril adulteration of the drinking water, young rats significantly increased daily ingestion of 0.3 M NaCl when it was available as an alternative to water and significantly increased daily water intakes when only water was available, in terms of absolute and body weight-adjusted intakes. Old rats had no response to captopril treatment. These results add important new information to previous reports that aging rats have diminished thirst and nearabsent salt appetite responses to regulatory challenges. aging; drinking; diuresis; natriuresis; dehydration; hypovolemia ELDERLY HUMANS CONSUME ADEQUATE fluids on a daily basis (7). Yet dehydration is a major health risk for the elderly (5), and the elderly are susceptible to dehydration because of increased fluid losses (41). Aged kidneys have a decreased ability to concentrate urine (17, 27) and to conserve sodium (8), along with a relative resistance to vasopressin (25), and release less renin when challenged (6). These changes with age predispose the elderly to hypovolemia and dehydration because of the reduced ability to conserve water and sodium during times of relative water and sodium loss. The elderly have decreased thirst sensation (24, 26, 32). As a result, they are slower than young people to restore fluid balance after exercise-induced dehydration (19) and water deprivation (26). It thus appears that the elderly are more vulnerable to the consequences of physiological challenges to body fluid homeostasis and that diminished thirst in the elderly contributes to their problems of fluid balance (15).The capacities of the aging kidney have been extensively investigated in rat models of aging. As in elderly humans, kidneys of aging r...

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Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 94%

mentioning

confidence: 94%

mentioning

confidence: 99%

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Thirst and salt appetite responses in young and old Brown Norway rats

Thunhorst

Johnson²

2003

American Journal of Physiology-Regulatory, Integrative and Comp

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Thirst and Water‐Salt Appetite

Rowland

2002

Stevens' Handbook of Experimental Psychology

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In this chapter, the current theoretical concepts and known physiological mechanisms for mammalian fluid homeostasis are reviewed. Fluid loss from the intracellular fluid compartment is sensed by osmoreceptors, which are located peripherally in structures such as the liver as well as in the brain, and underlie osmotic or intracellular thirst and water intake. Fluid loss from the extracellular fluid compartment is sensed by pressure‐sensitive cardiopulmonary receptors, and underlies hypovolemic or extracellular thirst and water intake. The peptide hormone, angiotensin II, released during hypovolemia may contribute to extracellular thirst. Both types of dehydration produce vasopressin secretion; its primary role is to minimize further fluid loss from the kidney and it does not seem to contribute to thirst. Brain structures of the forebrain lamina terminalis are critically involved in transduction and integration of this neurosensory and hormonal information to engage drinking behavior, for example naturally‐occurring thirst such as after deprivation or during meals. Aspects of thirst during ontogeny and aging, as well as genetic and individual differences in thirst are discussed briefly. Extracellular dehydration involves loss of sodium as well as water, and so both preference and appetite for sodium, and the roles of the hormones aldosterone and angiotensin II are reviewed. Several problem areas in which our knowledge is less complete are also identified.

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