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PubMed1980

Cardiothoracic ratio as a guide to ultrafiltration therapy in dialyzed patients.

This study evaluated the cardiothoracic ratio (CTR) and the roentgenologic heart volume (RHV) as indexes of body fluid retention in 37 uremics on maintenance dialysis therapy. Both indexes related to a highly significant degree with the variations of body fluids balance assessed by the changes in body weights. Cardiomegaly (CTR greater than .500) subsided with adequate ultrafiltration therapy in most patients including those having blood pressure values within the normal range. It is concluded that the measurements of CTR provides an useful guide to ultrafiltration therapy especially in those patients whose blood pressure fails to sense the body fluid retention.

Adult↗
PubMed2005

Role of hypobaria in fluid balance response to hypoxia.

To estimate the separate and combined effects of reduced P(B) and O2 levels on body fluid balance and regulating hormones, measurements were made during reduced PB (altitude, ALT; P(B) = 432 mm Hg, F(I(O2)) = 0.207), reduced inspired O2 concentration (normobaric hypoxia, HYX; P(B) = 614 mm Hg, F(I(O2)) = 0.142), and lowered ambient pressure without hypoxia (normoxic hypobaria HYB; P(B) = 434 mm Hg, F(I(O2)) = 0.296). Nine fit and healthy young men were exposed to these conditions for 10 h in a decompression chamber. Lake Louise AMS scores, urine collections, and blood samples were obtained every 3 h, with recovery measurements 2 h after exposure. AMS was significantly greater during ALT than HYX, as previously reported (J. Appl. Physiol. 81:1908-1910. 1996), because the combination of reduced P(B) and P(O2) over the 10 h favored fluid retention by reducing urine volume, while plasma volume (PV) remained higher than during HYX. At ALT the plasma Na+ fell significantly at 6 h, probably from dilution of extracellular fluid, and antidiuretic hormone (ADH) was highest (p = 0.006 versus HYB). The PV, urine flow, free water clearance, and plasma renin activity (PRA) rose significantly during recovery from ALT as AMS symptoms subsided, suggesting increased intravascular fluid and reduced adrenergic tone. During HYB, the plasma aldosterone (ALDO) and K+ levels were significantly elevated, and PRA was highest and ADH lowest, without fluid retention. During HYX, fluid balance was similar to HYB, but PV and ALDO were significantly lower, and ALDO increased significantly in recovery from HYX. The fluid retention at ALT in AMS-susceptible subjects appears related to a synergistic interaction involving reduced P(B) and ADH and ALDO.

Acclimatization↗
PubMed1986

Lesions in lateral parabrachial nucleus enhance drinking to angiotensin II and isoproterenol.

The lateral parabrachial nucleus (LPBN) has been shown to be anatomically linked to a number of forebrain nuclei and medullary structures implicated in the control of body fluid balance and cardiovascular regulation. Although these connections suggest a role for the LPBN in body fluid homeostasis, there is currently little or no physiological or behavioral data to support this notion. The purpose of the present series of experiments was to determine the importance of the ventrolateral region of the LPBN (VLLPBN) in the behavioral response to various thirst challenges. Rats with electrolytic lesions of the VLLPBN and control rats were studied after administration of angiotensin II (ANG II) (1.5 and 3.0 mg/kg), isoproterenol (30 and 100 micrograms/kg), polyethylene glycol (20%) and hypertonic saline (4 and 12%). It was found that rats with lesions drank more in response to ANG II and isoproterenol administration than did control animals.

Angiotensin II↗
PubMed2001

Systemic administration of the long-acting GLP-1 derivative NN2211 induces lasting and reversible weight loss in both normal and obese rats.

Postprandial release of the incretin glucagon-like peptide-1 (GLP-1) has been suggested to act as an endogenous satiety factor in humans. In rats, however, the evidence for this is equivocal probably because of very high endogenous activity of the GLP-1 degrading enzyme dipeptidyl peptidase-IV. In the present study, we show that intravenously administered GLP-1 (100 and 500 microg/kg) decreases food intake for 60 min in hungry rats. This effect is pharmacologically specific as it is inhibited by previous administration of 100 microg/kg exendin(9-39), and biologically inactive GLP-1(1-37) had no effect on food intake when administered alone (500 microg/kg). Acute intravenous administration of GLP-1 also caused dose-dependent inhibition of water intake, and this effect was equally well abolished by previous administration of exendin(9-39). A profound increase in diuresis was observed after intravenous administration of both 100 and 500 microg/kg GLP-1. Using a novel long-acting injectable GLP-1 derivative, NN2211, the acute and subchronic anorectic potentials of GLP-1 and derivatives were studied in both normal rats and rats made obese by neonatal monosodium glutamate treatment (MSG). We showed previously that MSG-treated animals are insensitive to the anorectic effects of centrally administered GLP-1(7-37). Both normal and MSG-lesioned rats were randomly assigned to groups to receive NN2211 or vehicle. A single bolus injection of NN2211 caused profound dose-dependent inhibition of overnight food and water intake and increased diuresis in both normal and MSG-treated rats. Subchronic multiple dosing of NN2211 (200 microg/kg) twice daily for 10 days to normal and MSG-treated rats caused profound inhibition of food intake. The marked decrease in food intake was accompanied by reduced body weight in both groups, which at its lowest stabilized at approximately 85% of initial body weight. Initial excursions in water intake and diuresis were transient as they were normalized within a few days of treatment. Lowered plasma levels of triglycerides and leptin were observed during NN2211 treatment in both normal and MSG-treated obese rats. In a subsequent study, a 7-day NN2211 treatment period of normal rats ended with measurement of energy expenditure (EE) and body composition determined by indirect calorimetry and dual energy X-ray absorptiometry, respectively. Compared with vehicle-treated rats, NN2211 and pair-fed rats decreased their total EE corresponding to the observed weight loss, such that EE per weight unit of lean body mass was unaffected. Despite its initial impact on body fluid balance, NN2211 had no debilitating effects on body water homeostasis as confirmed by analysis of body composition, plasma electrolytes, and hematocrit. This is in contrast to pair-fed animals, which displayed hemoconcentration and tendency toward increased percentage of fat mass. The present series of experiments show that GLP-1 is fully capable of inhibiting food intake in rats via a peripherally accessible site. The loss in body weight is accompanied by decreased levels of circulating leptin indicative of loss of body fat. The profound weight loss caused by NN2211 treatment was without detrimental effects on body water homeostasis. Thus, long-acting GLP-1 derivatives may prove efficient as weight-reducing therapeutic agents for overweight patients with type 2 diabetes.

Animals↗
PubMed1999

Drink composition, voluntary drinking, and fluid balance in exercising, trained, heat-acclimatized boys.

This study examined the effects of beverage composition on the voluntary drinking pattern, body fluid balance, and thermoregulation of heat-acclimatized trained boys exercising intermittently in outdoor conditions (wet bulb globe temperature 30.4 +/- 1.0 degreesC). Twelve boys (age 13.4 +/- 0.4 yr) performed two 3-h sessions, each consisting of four 20-min cycling bouts at 60% maximal aerobic power alternating with 25-min rest. One of two beverages was assigned: unflavored water (W) or flavored water plus 6% carbohydrate and 18 mmol/l Na (CNa). Drinking was ad libitum. Total intake was higher (P < 0.05) during CNa (1,943 +/- 190 g) compared with W (1,470 +/- 143 g). Euhydration was maintained with CNa (+0.18% body wt), but a mild dehydration resulted with W (-0.94% body wt; P < 0.05). Sweat loss, much higher than previously published for children of similar age, was similar between conditions (CNa = 1,644.7 +/- 117.5; W = 1,750.2 +/- 152.7 g). The increase in rectal temperature (CNa = 0.86 +/- 0.3; W = 0.76 +/- 0.1 degreesC), heart rate, and all perceptual variables did not differ between conditions. In conclusion, a flavored carbohydrate-electrolyte drink prevents voluntary dehydration in trained heat-acclimatized boys exercising in a tropical climate despite their large sweat losses. Because hydration changes were minor, the thermoregulatory strain observed was similar between conditions.

Acclimatization↗
PubMed2001

Water and sodium balance in space.

We have previously shown that fluid balances and body fluid regulation in microgravity (microG) differ from those on Earth (Drummer et al, Eur J Physiol 441:R66-R72, 2000). Arriving in microG leads to a redistribution of body fluid-composed of a shift of fluid to the upper part of the body and an exaggerated extravasation very early in-flight. The mechanisms for the increased vascular permeability are not known. Evaporation, oral hydration, and urinary fluid excretion, the major components of water balance, are generally diminished during space flight compared with conditions on Earth. Nevertheless, cumulative water balance and total body water content are stable during flight if hydration, nutritional energy supply, and protection of muscle mass are at an acceptable level. Recent water balance data disclose that the phenomenon of an absolute water loss during space flight, which has often been reported in the past, is not a consequence of the variable microG. The handling of sodium, however, is considerably affected by microG. Sodium-retaining endocrine systems, such as renin-aldosterone and catecholamines, are much more activated during microG than on Earth. Despite a comparable oral sodium supply, urinary sodium excretion is diminished and a considerable amount of sodium is retained-without accumulating in the intravascular space. An enormous storage capacity for sodium in the extravascular space and a mechanism that allows the dissociation between water and sodium handling likely contribute to the fluid balance adaptation in weightlessness.

Aldosterone↗
PubMed1987

Brain mechanisms and drinking: the role of lamina terminalis-associated systems in extracellular thirst.

Concomitants associated with alterations in body fluid balance serve as stimuli to appraise the brain of the momentary status of body salt and water. Extracellular fluid osmolality and the peptide ANG II have been identified as the humoral components that act as stimuli to trigger central receptors related to cellular and extracellular thirst, respectively. In the case of extracellular thirst, information about pressure/volume status is also obtained from systemic vascular receptors. It is proposed that peripherally-derived neural information is integrated with ANG II-related input within structures located in periventricular tissue of the AV3V.

Angiotensin II↗
PubMed2000

Interface Properties of Circumventricular Organs in Salt and Fluid Balance.

The "sensory" circumventricular organs, with their leaky blood-brain barriers, permit contact between brain neurons and blood-borne molecules. Body fluid balance and cardiovascular control involve established interface functions of subfornical organs. Their recently identified target functions for hormones released during digestion suggest that they may coordinate fluid and food intake.

Journal Article↗
PubMed1993

Rowing performance, fluid balance, and metabolic function following dehydration and rehydration.

Eight international class lightweight rowers were examined to determine the efficacy of rehydrating with water following 24 h of dehydration on body fluid balance, metabolic function, and rowing performance. The rowers performed a maximal rowing trial on a Gjessing rowing ergometer (4200 revs, 3-kg resistance) while euhydrated (ET) and following partial rehydration (RT). Body weight was reduced using exercise together with food and fluid restriction over 24 h and was followed by consumption of 1.5 l of water over 2 h. Body weight decreased 5.16 +/- 0.14% (P < 0.05) and plasma volume decreased 12.5 +/- 1.4% (P < 0.05) after dehydration. Rehydration restored plasma volume by 6.02 +/- 0.62%. Rowing trial time increased significantly from 7.02 +/- 0.17 min for the ET to 7.38 +/- 0.21 min for the RT (P < 0.05). The net plasma lactate accumulation decreased significantly from 8.77 +/- 0.31 mmol.l-1 for the ET to 6.77 +/- 0.24 mmol.l-1 for the RT (P < 0.05). Glycogen content (glycosyl units) of the vastus lateralis decreased by 203.6 +/- 18.6 mmol.kg-1 DW during the ET compared with 139.9 +/- 13.4 mmol.kg-1 DW during the RT (P < 0.05). These results demonstrate that the dehydration/rehydration protocol reduced maximal rowing performance due to lowered plasma volume and decreased muscle glycogen utilization.

Adult↗
PubMed1999

Responses to exercise, fluid, and energy balances during Ramadan in sedentary and active males.

This study compares the effects of the Ramadan fast (RF) on body and plasma compositions, hematology, and responses to steady state submaximal exercise in six physically active (A, 35.5+/-1.6 y) and seven sedentary (S, 37.6+/-2.3 y) Kuwaiti men. Subjects were evaluated: 1) 1 wk before RF (pre-RF); 2) 2 wk after the start of RF (mid-RF); 3) at the 4th wk of RF (end-RF). Total body weight and body fat decreased insignificantly (<1.5%, P>0.3) in both groups. At the end of Ramadan, significant increases in osmolarity (P<0.05), Na (P<0.05) and bicarbonate (P<0.05), and a decrease in serum iron were noted in sedentary but not in active subjects. Platelet count was lower in both groups by the end of RF (P<0.05). Body weight and percent fat changed little (<1.5%) in either group. During RF, submaximal exercise heart rate declined insignificantly in group S but significantly (P<0.05) in group A. The respiratory exchange ratio R during steady state submaximal exercise decreased markedly (P<0.001) by the end of RF in both groups. It is concluded that energy balance is well maintained during RF both in S and in A subjects. Metabolic adaptations during RF result in lower exercise R due to increased lipid usage. Deficits or redistribution of specific micronutrients (iron, vitamins) may account for reductions in serum iron and platelet counts, particularly in sedentary subjects that need to limit intake to maintain body weight. The decrease in submaximal exercise heart rate indicates that during RF, cardiovascular adaptation to conditioning is adequate in the more physically active group. Body fluid balance was better maintained in active than in sedentary subjects.

Adult↗
PubMed1999

Effects of oral contraceptives on body fluid regulation.

To test the hypothesis that estrogen reduces the operating point for osmoregulation of arginine vasopressin (AVP), thirst, and body water balance, we studied nine women (25 +/- 1 yr) during 150 min of dehydrating exercise followed by 180 min of ad libitum rehydration. Subjects were tested six different times, during the early-follicular (twice) and midluteal (twice) menstrual phases and after 4 wk of combined [estradiol-norethindrone (progestin), OC E + P] and 4 wk of norethindrone (progestin only, OC P) oral contraceptive administration, in a randomized crossover design. Basal plasma osmolality (P(osm)) was lower in the luteal phase (281 +/- 1 mosmol/kgH(2)O, combined means, P < 0.05), OC E + P (281 +/- 1 mosmol/kgH(2)O, P < 0.05), and OC P (282 +/- 1 mosmol/kgH(2)O, P < 0. 05) than in the follicular phase (286 +/- 1 mosmol/kgH(2)O, combined means). High plasma estradiol concentration lowered the P(osm) threshold for AVP release during the luteal phase and during OC E + P [x-intercepts, 282 +/- 2, 278 +/- 2, 276 +/- 2, and 280 +/- 2 mosmol/kgH(2)O, for follicular, luteal (combined means), OC E + P, and OC P, respectively; P < 0.05, luteal phase and OC E + P vs. follicular phase] during exercise dehydration, and 17beta-estradiol administration lowered the P(osm) threshold for thirst stimulation [x-intercepts, 280 +/- 2, 279 +/- 2, 276 +/- 2, and 280 +/- 2 mosmol/kgH(2)O for follicular, luteal, OC E + P, and OC P, respectively; P < 0.05, OC E + P vs. follicular phase], without affecting body fluid balance. When plasma 17beta-estradiol concentration was high, P(osm) was low throughout rest, exercise, and rehydration, but plasma arginine vasopressin concentration, thirst, and body fluid retention were unchanged, indicating a lowering of the osmotic operating point for body fluid regulation.

Adult↗
PubMed1985

The periventricular anteroventral third ventricle (AV3V): its relationship with the subfornical organ and neural systems involved in maintaining body fluid homeostasis.

The periventricular tissue surrounding the anteroventral third ventricle (AV3V) is critically involved in the maintenance of normal body fluid balance and distribution. The present review examines the anatomical, neurochemical, and functional relationship of the AV3V with neural systems subserving body fluid homeostasis. In particular, the nature of AV3V afferents from the subfornical organ (SFO) and from brainstem noradrenergic cell groups is discussed. A model is presented proposing that specific structures within the AV3V, particularly along the ventral lamina terminalis, function to integrate information derived from blood-borne angiotensin II (via the SFO) with input arising from vascular pressure/volume receptors. The resultant of this integration is important for the generation of a normal component of thirst (i.e., drinking) associated with extracellular dehydration.

Afferent Pathways↗