Urinary concentrating defect in the aged rat

Bengele, H. H.; Mathias, Robert; Perkins, John H.; Alexander, E. A.

doi:10.1152/ajprenal.1981.240.2.f147

Cited by 47 publications

(49 citation statements)

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“…However, UV was also greater in old rats, both as absolute and body weight-adjusted measures, and the urine from old rats was more dilute. This is consistent with the reduced concentrating ability of the aged kidney that has been observed by others (4,16,21,23).…”

Section: Discussionsupporting

confidence: 92%

“…As in elderly humans, kidneys of aging rats have diminished capacity to concentrate urine (4,16,21,23) and to release renin when challenged (1-3, 28). However, there are only a few studies in aging rats investigating the capacities of behavioral systems, namely, thirst and salt appetite, to supply sufficient water and sodium to maintain adequate hydration.…”

mentioning

confidence: 99%

“…However, there are only a few studies in aging rats investigating the capacities of behavioral systems, namely, thirst and salt appetite, to supply sufficient water and sodium to maintain adequate hydration. 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.…”

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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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: Discussionsupporting

confidence: 92%

mentioning

confidence: 99%

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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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“…For example, the aging kidney has reduced concentrating ability (6), and old rats excrete loads of water and hypotonic saline more slowly than young rats (34). Following administration of hypertonic saline loads, old rats ultimately excrete a greater fraction of the injected sodium than young rats (34,40) by producing a larger volume of dilute urine (40).…”

Section: Discussionmentioning

confidence: 99%

Hypotension- and osmotically induced thirst in old Brown Norway rats

Thunhorst¹,

Beltz²,

Johnson³

2009

American Journal of Physiology-Regulatory, Integrative and Comp

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Thunhorst RL, Beltz TG, Johnson AK. Hypotension-and osmotically induced thirst in old Brown Norway rats. Am J Physiol Regul Integr Comp Physiol 297: R149 -R157, 2009. First published May 6, 2009 doi:10.1152/ajpregu.00118.2009.-Compared to young cohorts, old rats drink less water in response to several thirst-inducing stimuli. In these experiments, we characterized water drinking in response to hypotension and cellular dehydration in young (4 mo), middle-aged adult (12 mo) and old (29 -30 mo) male Brown Norway rats. We injected the vasodilator, minoxidil as an intravenous bolus in a range of doses (0 -20 mg/kg), so that drinking responses could be compared at equivalent reductions of arterial pressure. Old rats had greatly diminished reflex tachycardia and became significantly more hypotensive after minoxidil compared with young and middle-aged rats. When compared at equivalent reductions of arterial pressure, old rats drank one-third as much as middle-aged rats, and one-fifth as much as young rats. In addition, there were age-related deficits in drinking in response to a range of administered loads of sodium (0.15-2 M NaCl, 2 ml/100 g body wt). Urinary excretion of water and sodium in response to the loads was equivalent across ages. Both middle-aged and old rats were less able than young rats to repair their water deficits after sodium loading, attributable almost entirely to their reduced drinking responses compared with young rats. Lastly, agerelated declines in drinking appeared to be more severe in response to hypotension than in response to cellular dehydration. aging; drinking; diuresis; natriuresis; dehydration; blood pressure; heart rate ELDERLY PEOPLE AND OLD ANIMALS have impaired drinking responses to many thirst-inducing challenges (21, 23, 25, 28, 29, 33-35, 40, 41). However, the nature of the underlying causes of reduced drinking that accompanies old age, such as impaired neural or humoral signaling mechanisms, remain largely undetermined. Knowledge of the causes of age-related declines in drinking will increase our understanding of the ways to help the elderly maintain better fluid homeostasis. This is an important consideration for an increasingly aging population and for the relationship between hydrational status and disorders, such as heat-related injury.Hypotension is a potent stimulus of thirst in rats (e.g., 10,17,18,26,30,38). Thirst following hypotension is due mainly to release of renin and formation of ANG II in the circulation (26, 38; for a review, see Ref. 20) and is blocked by interfering with the actions of, or formation of, ANG II (10,26,33,38). There are conflicting reports about whether old rats drink less in response to hypotension. For example, old rats have been found to drink less after subcutaneous injections of isoproterenol compared with young rats (24, 34, 37), although not always (25,34). These previous studies did not record arterial pressure or control for differences in arterial pressure that may occur with aging (24,25,34,37). This information is important becau...

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“…Control male and female animals had lower urine osmolality at 12 months of age compared to 2-4 months, suggesting urineconcentrating capacity had declined with age. Declining urine concentrating capacity has been observed in elderly humans (Rowe et al, 1976;Phillips et al, 1984) as well as studies of ageing animals (Bengele et al, 1981;Perucca et al, 2007;Singh et al, 2011). This decline is multifactorial, linked to progressive loss of functional glomeruli, reduced secretion of vasopressin (Tian et al, 2004), impaired cellular response to vasopressin (Beck & Yu, 1982;Corman et al, 1992;Geelen & Corman, 1992) and reduced GFR (Levinsky et al, 1959).…”

Section: Urinary Excretion Under Basal Conditionsmentioning

confidence: 98%

Gestational hypoxia and programming of disease

Walton¹

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Fetal hypoxia remains the most common complication throughout pregnancy and has a wide aetiology including, but not limited to, placental insufficiency, high altitude living and maternal factors such as smoking and pulmonary disease. Intrauterine growth restriction and subsequent low birth weight are common features of pregnancies complicated by reduced oxygenation. Suboptimal organ development may arise, thereby substantially increasing vulnerability to cardiovascular and renal diseases in adulthood. Recently it has been established that prenatally programmed vulnerability to disease may be exacerbated by a postnatal 'second-hit', such as a high salt diet or ageing. The primary aim of this thesis was to investigate the effects of maternal hypoxia on the programming of cardiovascular and renal disease in mice, and secondly whether excess dietary salt intake throughout life may exacerbate disease outcomes.Pregnant CD1 mice were housed in a hypoxia chamber set to 12% oxygen throughout the last five days of pregnancy, from embryonic day (E) 14.5 until birth (P0). Control animals remained in normoxic room conditions (21% oxygen) throughout pregnancy. Upon littering, animals were removed from the hypoxia chamber and raised in normoxic room conditions. A subset of mice was fed a high salt diet from 10 weeks of age until post-mortem. Mice were housed in metabolic cages for 24 hours to assess renal function under basal conditions, and in response to a 24 hour water deprivation challenge, at 4 and 12 months of age. Blood pressure and microvascular function and structure were assessed in offspring at 12 months of age.Kidneys, hearts and aortas were collected for stereological and histological analyses.Prenatal hypoxia reduced nephron number in the kidneys of male offspring, leading to glomerular hypertrophy, renal fibrosis and mild albuminuria by 12 months of age. However, female offspring exposed to the same hypoxic insult in utero presented with normal number of glomeruli and renal pathology equivalent to control animals by 12 months of age. Both male and female hypoxia-exposed offspring had elevated mean arterial pressure at 12 months of age. A high salt diet throughout adult life increased cardiac tissue fibrosis, particularly in male hypoxia-exposed offspring, and exacerbated renal pathology in male hypoxia-exposed offspring only. Pressurized myography was performed at the time of post-mortem to assess functional, structural and mechanical properties of mesenteric resistance arteries at 12 months of age. Both male and female offspring exposed to maternal hypoxia had significantly 3 impaired endothelial function, which was not exacerbated by the high salt diet. The combination of prenatal hypoxia and a postnatal high salt diet caused marked stiffening of the microvasculature as well as loss of elastin integrity and increased collagen content in the aorta, consistent with vascular stiffness. This suggests that kidneys from female offspring are somehow protected from the in utero insult; however, this protection...

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Urinary concentrating defect in the aged rat

Cited by 47 publications

References 10 publications

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

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

Hypotension- and osmotically induced thirst in old Brown Norway rats

Gestational hypoxia and programming of disease

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