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PubMed2002

Children at risk of developing dehydration from diarrhoea: a case-control study.

To identify the factors related to dehydration from diarrhoea, a hospital-based case-control study was carried out among under-2-year-old Bangladeshi children. The study compared 80 cases who had 'some' or severe dehydration with 160 age-matched controls who had 'no signs' of dehydration. All the cases and controls were examined and the mothers were interviewed in the hospital and followed at home on the 14th day of illness. Thirty-eight factors were studied for their probable influence on the development of dehydration. In bivariate analysis, 17 factors were found to be associated significantly with the development of dehydration and were treated with stepwise logistic regression analysis. A combination of vomiting, oral rehydration therapy at home, mother's dirty finger nails, and residing more than 3 km away from the hospital provided the maximum sensitivity (77.5 per cent) and specificity (91.2 per cent) for predicting development of dehydration. These prognostic factors would be helpful for community health workers to identify children at risk of developing diarrhoea-associated dehydration, and preventive strategies could be designed to alter the prognostic factors.

Bangladesh↗

PubMed1993

Comparative nephrotoxicity of carboplatin and cisplatin in euvolemic and dehydrated rats.

The aim of this study was to compare the renal tolerance of cisplatin and carboplatin in euvolemic and dehydrated rats. A total of 79 euvolemic or dehydrated male rats were randomly assigned to receive cisplatin (5 mg/kg body weight, i.p.), carboplatin (40 mg/kg body weight, i.p.) or vehicle. Body weight, serum creatinine, creatinine clearance, fractional excretion of sodium and urinary NAG excretion were recorded on days 1 and 5. Glomerular filtration rate (GFR), effective renal plasma flow (ERPF) and renal histology were determined on day 5. In the euvolemic and dehydrated control and carboplatin groups we observed no change in serum electrolytes, serum creatinine, creatinine clearance, GFR and ERPF. In the euvolemic and dehydrated control groups we observed no change in urinary NAG excretion. Carboplatin induced a slight but significant increase in urinary NAG excretion. In dehydrated rats carboplatin induced a significantly higher increase in urinary NAG excretion than in euvolemic rats. Cisplatin induced a marked and significant decrease in GFR and ERPF, and a significant increase in NAG. Dehydration markedly potentiated cisplatin nephrotoxicity. Euvolemic rats treated with cisplatin exhibited slight renal lesions with a mean score which was similar to the control group. The most extensive lesions were observed in euvolemic and dehydrated cisplatin treated rats with tubular necrosis in the outer stripe of the medulla.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1996

How valid are clinical signs of dehydration in infants?

Our objective was to determine the ability of several clinical signs of dehydration to distinguish among degrees of dehydration in infants with acute diarrhea. The design was a prospective cohort study in a pediatric referral hospital in Cairo, Egypt. Infant boys, 3-18 months old, with a history of acute diarrhea (5 or more watery stools per day for no more than 7 days) were eligible, except those with frank protein-energy malnutrition, serious nongastrointestinal illness, or being exclusively breast-fed. Several clinical signs of dehydration were assessed upon study entry. Subjects were then rehydrated with an oral rehydration solution and fed a standardized diet until diarrhea ceased (no watery or loose stools for 16 h). The main outcome measure was percent body weight gain at rehydration and at resolution of illness. Data from 135 subjects were available for analysis. Average (SD) rehydration phase duration was 5.2 (2.1) h, and average (SD) duration of illness was 54.5 (38) h. Multiple regression analysis selected prolonged skinfold, altered neurologic status, sunken eyes, and dry oral mucosa as the clinical signs that correlated best with percent dehydration (R2 for model 0.244, p < 0.001). Mean weight gain for the two assessment systems was 3.6-3.9% for mild, 4.9-5.3% for moderate, and 9.5-9.8% for severe dehydration. The most valid clinical signs of dehydration include prolonged skinfold, altered neurologic status, sunken eyes, and dry oral mucosa. Children with clinical signs of mild or moderate dehydration have fluid deficits on the order of 3 or 5% body weight, respectively.

Acute Disease↗

PubMed1998

Clinical and laboratory evaluation and management of children with vomiting, diarrhea, and dehydration.

Dehydration is responsible for the morbidity and, rarely, mortality secondary to vomiting and diarrhea from acute gastroenteritis. Despite the abundance of literature in the last 20 to 30 years focused on the treatment of dehydration with oral rehydration therapy, few studies have focused on the actual clinical diagnosis of dehydration. Conventional classification systems for assessing dehydration have not been subjected to rigorous prospective validation until recently. This article reviews the recent clinical evidence that validates the use of clinical signs and symptoms in assessing dehydration in children. The utility and limitations of measuring capillary refill time as a sign are also reviewed. In addition, the scant literature examining the utility of laboratory studies in evaluating dehydration is summarized. Oral rehydration therapy for the management of dehydration in children is reviewed. Finally, recent literature examining the effectiveness and advantages of rapid intravenous rehydration in the outpatient setting is discussed.

Blood Urea Nitrogen↗

PubMed1988

Aspirin enhances evaporation in hydrated and dehydrated rats.

The effect of acetysalicylic acid (aspirin) on thermoregulation in a warm environment was studied in hydrated and dehydrated adult rats to test the hypothesis that dehydration hyperthermia can be modified by an antipyretic drug. Metabolic rate (MR), evaporative water loss (EWL), and deep body temperature (Tb) were measured during 2 h of exposure to an ambient temperature of 36 degrees C after the rats had received an oral pellet of aspirin (100 mg.kg-1) or placebo. The dehydrated placebo group had a higher Tb and lower EWL than the hydrated placebo group. Aspirin increased MR and EWL in both hydrated and dehydrated animals. Aspirin did not affect Tb in hydrated rats, but reduced Tb by 0.2 degree C in dehydrated rats during the heat exposure. The elevation in EWL appears to be a thermoregulatory response to increased heat production in both hydrated and dehydrated animals after aspirin treatment. The possibility that aspirin may act in dehydrated animals to restore central thermosensitivity toward hydrated levels needs to be tested further.

Animals↗

PubMed1985

Pituitary and adrenal hormone responses to naloxone in euhydrated and dehydrated dogs.

To assess the role of endogenous opioids in the secretion of pituitary and adrenal hormones, we injected intravenously the antagonist naloxone (1 mg/kg) into six dogs, euhydrated or dehydrated. Plasma renin activity (PRA), osmolality, and concentrations of adrenocorticotropic hormone (ACTH), cortisol, aldosterone, vasopressin, Na+, and K+ were measured. Dehydration elevated (P less than 0.05) PRA, vasopressin, osmolality, and Na+. Thirty minutes after injection of naloxone, osmolality, Na+, K+, hematocrit, and plasma protein were not altered. Naloxone-induced elevations of ACTH (25 +/- 10 and 22 +/- 4 pg/ml) and cortisol (4.8 +/- 1.0 and 5.1 +/- 1.0 micrograms/dl) were similar during euhydration and dehydration, respectively. The increase in aldosterone due to naloxone was greater after euhydration (7.7 +/- 3 ng/dl) than during dehydration (2.3 +/- 0.8 ng/dl). Naloxone increased vasopressin by (5.3 +/- 2.8 microU/ml) during dehydration but not during euhydration. Intravenous hypertonic saline infusions showed that naloxone potentiates the osmotic release of vasopressin. Our results indicated that dehydration did not alter the inhibitory role of opioids in regulation of ACTH and cortisol but suppressed the inhibition of aldosterone secretion. Our findings also showed that opioids inhibit secretion of vasopressin during dehydration by decreased responsiveness to osmotic stimulation.

Adrenocorticotropic Hormone↗

PubMed1988

Influence of dehydration on locally mediated hindlimb vasodilation in baboons.

Previous studies indicate that the heat stress-induced cutaneous vasodilation in baboons is attenuated during dehydration by mechanisms other than the well-known neurohumoral vasoconstrictor mechanisms. Therefore, this study sought to determine whether dehydration also attenuates locally mediated maximum hindlimb blood flow and vascular conductance in baboons. Five baboons were chronically instrumented to measure arterial blood pressure and mean external iliac artery blood flow (MIBF). Hindlimb vasodilation was induced by occlusions of the external iliac artery for 2.5, 5.0, 7.5, and 10.0 min and by close-arterial injections of acetylcholine (ACh) and sodium nitroprusside (NP) in graded doses. These vasodilatory stimuli were applied in euhydrated and dehydrated states, the latter being produced by water deprivation for 64-68 h. Maximum MIBF and iliac vascular conductance (IVC) after arterial occlusion were reduced by 67-70% during dehydration. Also, maximum MIBF and IVC produced by ACh in the dehydrated state were 46-52% lower than in the euhydrated state. A similar reduction in the responses to NP occurred during dehydration. It is concluded that the maximum hindlimb blood flow and vascular conductance produced by local, nonneurohumoral mechanisms are attenuated in the baboon during dehydration.

Acetylcholine↗

PubMed1986

Attenuation of hindlimb vasodilation in heat-stressed baboons during dehydration.

The influence of dehydration on hindlimb vasodilation during environmental heating (EH) was examined in eight unanesthetized chronically instrumented baboons. Mean iliac blood flow (MIBF), arterial blood pressure, and core temperature (Tc) were measured during EH of baboons in euhydrated and dehydrated states. EH consisted of acute exposure to high ambient temperatures (39-44 degrees C) until Tc reached 39.5 degrees C. Dehydration was produced by 68-72 h of fluid deprivation, which caused increases in plasma osmolality [291 +/- 1 (SE) to 338 +/- 6 mosmol/kg H2O] and sodium concentration (143 +/- 2 to 163 +/- 3 meq/l) and a 16% fall in plasma volume. The primary influence of dehydration was attenuation of the progressive rise in MIBF and iliac conductance (IC) during EH. Absolute MIBF and IC levels at Tc = 39.5 degrees C during EH were 44 and 52%, respectively, lower in the dehydrated state. Also, the MIBF-Tc and IC-Tc linear regression coefficients during EH were lower by 33 and 43%, respectively, in the dehydrated state. Since limb skeletal muscle blood flow does not increase during EH, we conclude that dehydration attenuates the heat stress-induced rise in skin blood flow in baboons, an influence that is similar to what occurs in humans.

Animals↗

PubMed1994

Plasma volume conservation in pigeons: effects of air temperature during dehydration.

We assessed the effects of the ambient air temperature prevailing during dehydration, which included complete water and food deprivation, on plasma volume (PV) conservation in pigeons (Columba livia) exposed to air temperatures of 25 degrees C (n = 7), 36 degrees C (n = 12), and 40 degrees C (n = 24). The pigeons were dehydrated for 65.4, 32.3, and 27.7 h, on average, at 25, 36, and 40 degrees C, respectively. Dehydration rates averaged 5, 10, and 15.2% of initial total body water (TBW) per day at the three air temperatures, in ascending order. Birds exposed to 25 and 36 degrees C maintained PV despite the fact that they lost, on average, 14 and 17.3% of their TBW, respectively. In contrast, PV in pigeons exposed to 40 degrees C decreased by 8.9%, even though the reduction in TBW (17.7%) was similar to that incurred at 36 degrees C. Mean plasma osmolalities reached 347.7, 345.6, and 374.8 mosmol/kgH2O at 25, 36, and 40 degrees C, respectively. No significant changes occurred in hematocrit (Hct) and hemoglobin concentrations (Hb) during dehydration at 25 and 36 degrees C. However, at 40 degrees C Hb increased by 8.2% with no change in Hct, indicating a decrease in red blood cell volume (RBCV). The results of this study suggest that maintenance of PV and RBCV is affected not only by the dehydration level attained but also by the ambient conditions under which dehydration is induced and the rate at which dehydration takes place.

Animals↗

PubMed1999

Effect of an exercise-heat acclimation program on body fluid regulatory responses to dehydration in older men.

We examined if an exercise-heat acclimation program improves body fluid regulatory function in older subjects, as has been reported in younger subjects. Nine older (Old; 70 +/- 3 yr) and six younger (Young; 25 +/- 3 yr) male subjects participated in the study. Body fluid regulatory responses to an acute thermal dehydration challenge were examined before and after the 6-day acclimation session. Acute dehydration was produced by intermittent light exercise [4 bouts of 20-min exercise at 40% peak rate of oxygen consumption (VO(2 peak)) separated by 10 min rest] in the heat (36 degrees C; 40% relative humidity) followed by 30 min of recovery without fluid intake at 25 degrees C. During the 2-h rehydration period the subjects drank a carbohydrate-electrolyte solution ad libitum. In the preacclimation test, the Old lost approximately 0.8 kg during dehydration and recovered 31 +/- 4% of that loss during rehydration, whereas the Young lost approximately 1.2 kg and recovered 56 +/- 8% (P < 0.05, Young vs. Old). During the 6-day heat acclimation period all subjects performed the same exercise-heat exposure as in the dehydration period. Exercise-heat acclimation increased plasma volume by approximately 5% (P < 0.05) in Young subjects but not in Old. The body fluid loss during dehydration in the postacclimation test was similar to that in the preacclimation in Young and Old. The fractional recovery of lost fluid volume during rehydration increased in Young (by 80 +/- 9%; P < 0.05) but not in Old (by only 34 +/- 5%; NS). The improved recovery from dehydration in Young was mainly due to increased fluid intake with a small increase in the fluid retention fraction. The greater involuntary dehydration (greater fluid deficit) in Old was accompanied by reduced plasma vasopressin and aldosterone concentrations, renin activity, and subjective thirst rating (P < 0.05, Young vs. Old). Thus older people have reduced ability to facilitate body fluid regulatory function by exercise-heat acclimation, which might be involved in attenuation of the acclimation-induced increase in body fluid volume.

Acclimatization↗

PubMed2005

P2Y2 receptor mRNA and protein expression is altered in inner medullas of hydrated and dehydrated rats: relevance to AVP-independent regulation of IMCD function.

Arginine vasopressin (AVP), acting through a cAMP second messenger system, regulates osmotic water permeability (Pf) of the collecting duct. In the collecting duct, the activities of cAMP and phosphonositides (PI) are mutually inhibitory. The P2Y2 receptor (P2Y2-R) is a G protein-coupled extracellular nucleotide receptor associated with PI signaling pathway. Previously, we showed that P2Y2-R is expressed in inner medullary collecting duct (IMCD) of rat, and its agonist (ATP/UTP) activation decreased AVP-induced Pf and resulted in enhanced production of prostaglandin E2. Hydrated and dehydrated states are associated with alterations in the circulating levels of AVP, expression and/or subcellular distribution of AVP-regulated aquaporin-2 water channel in IMCD and thus Pf of IMCD. We hypothesized that altered expression and/or signaling via P2Y2-R may also modulate IMCD function in these conditions. Sprague-Dawley rats were subjected to dehydration by water deprivation (48 h) or hydration (48 or 96 h) by providing sucrose water. Hydration or dehydration resulted in marked alterations in mRNA expression (Northern blot analysis and real-time RT-PCR) and protein abundance (Western blot analysis) of P2Y2-R, with hydrated rats showing significantly higher levels compared with dehydrated rats. Sequential hydration and dehydration experiments also revealed that the regulated expression profiles of P2Y2-R mRNA and protein are discordant. Conversely, the expression of V2-R mRNA remained unaltered during hydration and dehydration. Because virtually all renal cells release ATP in a regulated fashion, the observed alterations in P2Y2-R expression in the inner medulla in hydrated and dehydrated states may constitute a novel mechanism of purinergic modulation of IMCD function.

Animals↗

PubMed1978

Response of the renin-aldosterone system in the camel to acute dehydration.

Plasma renin activity (PRA), renin substrate concentration (PRS), aldosterone concentration (PA), and cortisol levels were determined in five camels during dehydration (8-10 days complete denial of water) and at timed intervals after rapid rehydration in cool spring and hot summer weather. Plasma sodium concentration increased from 138 +/- 3.7 to 147 +/- 2.5 (mean +/- SE) meq/l during spring dehydration, and from 146 +/- 1.3 to 157 +/- 1.14 meq/l during dehydration in the summer. Plasma sodium concentration returned to control levels over the course of several hours following rapid rehydration. Only minor changes in plasma potassium concentration occurred. The hormonal changes were accentuated in the summer dehydration. PRA increased slightly on dehydration, and returned to control levels over the course of several hours following rehydration. PA increased slightly on dehydration but was markedly elevated 24 h after rehydration. PRS showed a slight increase following rehydration in the spring experiment, but no significant change in the summer experiment. Changes in cortisol were insignificant. The results are consistent with a role for angiotensin and aldosterone in enhancing sodium and water reabsorption from kidney and large intestine on dehydration in this species.

Aldosterone↗

PubMed1979

Heat and acute dehydration effects on acceleration response in man.

Though heat and dehydration each impair acceleration tolerance, interactions among these stresses have not previously been studied. Seven men were dehydrated in heat by 0, 1, and 3% of body weight before a series of +Gz, gradual-onset centrifuge runs with the capsule first 38 degrees C, then 20 degrees C. Heat alone raised heart rate by 6.5 beats/min independent of other stresses. Dehydration and acceleration appeared to act synergistically in raising HR. Heat lowered relaxed G tolerance by 0.3 G; dehydration tended to lower G tolerance and increased the variability of response to heat. A high-tolerance subgroup (n = 4) could normally sustain +7 Gz for 60 s with anti-G suit and straining, but 3% dehydration reduced mean time to 35 s. Dehydration was associated with a decrease in the loss of plasma volume at 7 G. Heat-induced tolerance loss appears similar for both gradual- and rapid-onset centrifuge profiles. In contrast, dehydration effects are greater in rapid-onset runs, evidence that normal anti-G protective mechanisms can partly counteract the effect of fluid deficit. The results are relevant for crew members of high-performance aircraft, where unexpected diminution of their normally high G tolerance can have disastrous consequences.

Acceleration↗

PubMed2006

Study of erythrocyte ATPases in infants evaluated during the recovery phase of severe dehydration caused by diarrhea.

BACKGROUND/AIMS: Patients severely dehydrated from diarrhea are at risk of developing hyperkalemia consequent to fluid therapy treatment. In parallel with the regulation of external potassium balance by the kidney and gastrointestinal tract, plasma potassium is rapidly regulated by redistribution of potassium between the extracellular and intracellular compartments. Erythrocytes contain ATPases that play a role in this potassium movement. In this study, erythrocyte ATPase effectiveness was evaluated in infants dehydrated from diarrhea and compared to that of healthy infants. METHODS: Blood samples were collected from dehydrated and healthy infants. The activity of Na+,K+-ATPase and of an ouabain-insensitive K+-ATPase were assessed. Serum electrolytes and blood pH were also determined. RESULTS: No hyperkalemia was found, even in dehydrated infants presenting with severe hyperchloremic metabolic acidosis. In the erythrocytes of dehydrated infants, Na+,K+-ATPase activity was increased correlating positively with the amount of sodium administered. High K+-ATPase activity in the erythrocytes correlated with low plasma potassium. The K+-ATPase activity correlated positively with the amount of potassium administered to dehydrated infants. CONCLUSION: These findings suggest that the erythrocytes Na+,K+-ATPase and K+-ATPase both protect against plasma potassium abnormalities in dehydrated infants. In such infants, the risk of hyperkalemia is probably low.

Acidosis↗

PubMed1986

Dehydration increases the electrically evoked dopamine release from the neural and intermediate lobes of the rat hypophysis.

The effect of dehydration on dopamine (DA) release from the neural and intermediate lobes of the rat pituitary gland after electrical stimulation of the pituitary stalk was studied in vitro. The amount of DA released from pituitary lobes of dehydrated rats (no water for 72 h), in which the hormone secretion from the hypophysis, especially the neural lobe, is known to be greatly enhanced, was significantly higher when compared with that from control tissues. In control and dehydrated rats the evoked DA release from the intermediate lobe was higher than that from the neural lobe. After dehydration, the stimulus-evoked DA release from the neural lobe increased by more than 200%, whereas that from the intermediate lobe increased by only 60%, indicating a preferential activation of the DA system of the neural lobe. There was a decrease in DA released per pulse from the combined neuro-intermediate lobe of control rats with increasing number of stimulation pulses. In contrast, DA release per pulse from the neuro-intermediate lobe of dehydrated rats showed a tendency to increase with increasing number of pulses. As the availability of newly synthesized DA is believed to be the limiting factor for transmitter release, the present observations suggested a higher in vitro DA synthesis rate in the tissues from dehydrated rats. This agrees with in vivo results of Alper and his colleagues who found an increased accumulation of L-3,4-dihydroxyphenylalanine (DOPA) in neuro-intermediate lobes of dehydrated rats after inhibition of DOPA-decarboxylase.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2004

The effect of dehydration on wrestling minimum weight assessment.

UNLABELLED: Given that some wrestlers arrive for minimum weight (MW) testing in a dehydrated condition, it is important to understand the effects of dehydration on MW assessment methods. PURPOSE: To determine the effect of dehydration on the assessment of MW by three-site skinfolds with the Lohman formula (SF), leg-to-leg bioelectrical impedance analysis (BIA), and multifrequency bioelectrical impedance spectroscopy (BIS) compared with a four-component (4C) criterion. METHODS: Twenty-two male collegiate wrestlers (mean +/- SD, age: 19.9 +/- 1.4 yr, height: 174.0 +/- 6.8 cm, body mass: 77.4 +/- 9.1 kg) had their body composition assessed by the 4C criterion, hydrostatic weighing (HW), SF, BIA, and BIS in euhydration (EUH) and dehydration (DEH). Subjects dehydrated 2-5% of body weight through fluid restriction and exercise in a hot environment. RESULTS: In EUH, the total error (TE) for HW (1.75 kg) and SF (2.15 kg) were not significantly different, but the TE for HW and SF methods were significantly lower than the TE for both BIS (3.68 kg) and BIA (3.77 kg). In DEH, SF, BIA, and BIS methods had a TE approaching or exceeding 4 kg (8.8 lb). Dehydration increased the TE for SF and BIA through an artificial lowering of body weight and for BIS by an increased error in intracellular water prediction. CONCLUSION: Acute thermal dehydration violates assumptions necessary for the accurate and precise prediction of MW by SF, leg-to-leg BIA, and multifrequency BIS.

Adolescent↗

PubMed2025

Dehydration and rehydration in donkeys: the role of the hind gut as a water reservoir.

Body fluid distribution was measured in three donkeys, fully hydrated, following dehydration and after being rapidly rehydrated. In twenty other donkeys that were slaughtered to supply food for predators in a safari zoo, the water content in the different compartments of the gastrointestinal tract (GIT) was assessed. Prior to being slaughtered, four of the animals were fully hydrated, four dehydrated and 12 dehydrated, rehydrated and then slaughtered and examined, four at 1, for at 3 and four at 5 hours following drinking. When the body mass of dehydrated donkeys dropped to 75.4 +/- 2.4% of their initial value, total body water of the animals (HTO space), extracellular volume (SCN space) and plasma volume (EB space) were reduced to 76.6 +/- 5.3%, 80.9 +/- 10.6% and 73.2 +/- 8.3% of their initial values, respectively. The amount of water retained in the GIT of the fully hydrated donkeys amounted to 15.9 +/- 3.4 1, 19% of total body water. In the dehydrated donkeys it was only 7.4 +/- 1.3 1. The calculated total intracellular volume in the dehydrated donkeys was only 14% lower than in the fully hydrated animals. When drinking was allowed, dehydrated donkeys consumed 17.6 +/- 2.4 1 of water. The increase in the water content in the gut of newly rehydrated donkeys matched this volume, 80% of which was retained in the hind gut. During the five hours after drinking, only slow and moderate changes in the volume of the hind gut were recorded. Changes in plasma volume were also suppressed. It is suggested that the hind gut of the donkey, similar to the rumen of goats and sheep, plays a role as a water reservoir that helps maintain the osmotic stability of the body.

Animals↗

PubMed2002

Effects of dehydration on endocrine regulation of the electrolyte and fluid balance and atrial natriuretic peptide-binding sites in perinatally malnourished adult male rats.

OBJECTIVE: The first aim of this work was to investigate, under basal conditions in adult male rats, the long-term consequences of perinatal maternal food restriction on the plasma concentrations of vasopressin (VP), aldosterone and atrial natriuretic peptide (ANP) and on plasma renin activity (PRA). Furthermore, under these same conditions, the hypothalamic VP gene expression as well as the density (B(max)), affinity (K(d)) and gene expression of ANP receptors were determined in kidneys and adrenals. The second aim of this work was to examine the responsiveness to dehydration in perinatally malnourished rats. Thus, the latter parameters were studied in these rats after 72 h water deprivation. METHODS: This study was conducted on 4-Month-old male rats from mothers exposed to 50% food restriction (FR50) during the last week of gestation and lactation and on age-matched control animals (C). At this stage, both C and FR50 rats were killed by decapitation between 0900 h and 1000 h in order to determine parameters under basal conditions or after 72 h water deprivation. Plasma VP, ANP and aldosterone levels and PRA were determined by radioimmunoassay. Hypothalamic VP gene expression was determined in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) by in situ hybridization. The B(max) and K(d) values of ANP receptors were evaluated from Scatchard plots. ANP receptor gene expression was determined by Northern blot analysis. RESULTS: Under basal conditions, perinatal malnutrition reduced body weight, absolute weight of kidneys and adrenals, and haematocrit. Compared with control rats, FR50 rats had significantly greater plasma VP and aldosterone levels but PRA, plasma ANP levels, plasma osmolality and hypothalamic VP gene expression were not significantly different. Perinatal malnutrition did not significantly affect glomerular ANP receptor density, but in adrenals it decreased both B(max) and K(d) values of ANP-B receptors (biological receptors) and increased B(max) of ANP-C receptors (clearance receptors). ANP-B(A) (receptor subtype A of ANP-B receptors) receptor gene expression was not significantly affected, whereas ANP-C receptor gene expression was enhanced in both adrenals and kidneys in FR50 rats. After 72 h dehydration, control rats showed a significant rise in haematocrit, plasma osmolality, PRA, circulating levels of VP and aldosterone and VP gene expression in both PVN and SON but showed a decrease in plasma ANP levels. B(max) of ANP-B receptors was decreased whereas B(max) of ANP-C receptors was enhanced in both adrenals and kidneys. ANP-B(A) receptor gene expression was not significantly affected in either kidneys or adrenals in dehydrated control rats. Similarly, ANP-C receptor gene expression was unaffected in kidneys whereas it was significantly enhanced in adrenals. In FR50 rats, the effects of water deprivation were qualitatively similar to those reported in controls concerning plasma parameters except for plasma VP levels which tended to rise (not significant) but this increase was only very slight compared with controls. Moreover, unlike controls, VP gene expression in both PVN and SON was not enhanced after dehydration in FR50 rats. In kidneys, dehydrated FR50 rats, like controls, upregulated ANP-C receptors, but they were unable to downregulate ANP-B receptors. In adrenals, unlike controls, FR50 rats enhanced ANP-B receptor density whereas they decreased both ANP-C receptor density and expression after 72 h dehydration. Similar to controls, the expression of ANP-B(A) receptors in both kidneys and adrenals as well as the expression of ANP-C receptors in kidneys, were unaffected in dehydrated FR50 rats. CONCLUSION: Perinatal malnutrition had long-lasting effects on regulation of the fluid and electrolyte balance under basal conditions. The main effects were a significant rise in circulating levels of VP and aldosterone, and changes in density of adrenal ANP-binding sites and ANP-C receptor gene expression in both adrenals and kidneys. Perinatal malnutrition also affects the responsiveness to water deprivation with alterations in both hypothalamic VP gene expression and regulation of ANP-binding sites.

Adrenal Glands↗