Whole-body Sodium Concentration Research Articles

Normative Data for Sweat Rate and Whole-Body Sodium Concentration in Athletes Indigenous to Tropical Climate.

This study determined normative data for sweat rate (SR) and whole-body (WB) sweat sodium concentration [Na+] in athletes indigenous to a tropical climate, categorized by age, gender, and sport classification. We analyzed data from 556 athletes (386 adult and 170 young) in endurance (END), team/ball (TBA), and combat (COM) sports exercising in tropical environments (wet bulb globe temperature = 29.4 ± 2.1 °C). SR was calculated from change in body weight corrected for urine output and fluid/food intake. Sweat was collected using absorbent patches, and regional [Na+] was determined using an ion selective analyzer and normalized to WB sweat [Na+]. Data are expressed as mean ± SD. SR was higher in males compared with females in both young (24.2 ± 7.7ml·kg-1·hr-1 vs. 16.7 ± 5.7ml·kg-1·hr-1) and adult (22.8 ± 7.4 ml·kg-1·hr-1 vs. 18.6 ± 7.0ml·kg-1·hr-1) athletes, in END sports in girls (END = 19.1 ± 6.0 ml·kg-1·hr-1; TBA = 14.6 ± 4.5ml·kg-1·hr-1), and in adult males (END = 25.2 ± 6.3 ml·kg-1·hr-1; TBA = 19.1 ± 7.2 ml·kg-1·hr-1; COM = 18.4 ± 8.5ml·kg-1·hr-1) and females (END = 23.5 ± 5.6 ml·kg-1·hr-1; TBA = 14.2 ± 5.2 ml·kg-1·hr-1; COM = 15.3 ± 5.2ml·kg-1·hr-1); p < .05. WB sweat [Na+] was higher in adult athletes than in young athletes (43 ± 10mmol/L vs. 40 ± 9mmol/L, p < .05). These norms provide a reference range for low, low average, average high, and high SR and WB sweat [Na+], which serve as a guide for fluid replacement for athletes who live and train in the tropics.

Toxicokinetic Toxicodynamic (TKTD) Modeling of Ag Toxicity in Freshwater Organisms: Whole-Body Sodium Loss Predicts Acute Mortality Across Aquatic Species

ToxicoKinetic ToxicoDynamic (TKTD) models are considered essential tools to further advance acute toxicity prediction of metals for a range of species and exposure conditions, but they are currently underutilized. We present a mechanistic TKTD model for acute toxicity prediction of silver (Ag) in freshwater organisms. In this new approach, we explicitly link relevant TKTD processes to species (physiological) characteristics, which facilitates model application to other untested freshwater organisms. The model quantifies the reduction in whole-body sodium concentration over time as a function of the target site inhibition over time, the target site density and the species-specific sodium turnover rate. Freshwater species are assumed to die instantly when they have lost a critical amount of their initial whole-body sodium concentration. Results show that mortality is significantly related to sodium loss (r(2) = 0.86) for various aquatic organisms and exposure durations. The model accurately predicts lethal effect concentrations for different freshwater organisms, including Daphnia magna, rainbow trout and juvenile crayfish, and is able to capture the observed size-specific variation of nearly 2 orders of magnitude in empirical LC50s.

Physiological Stress in Native Southern Brook Trout During Episodic Stream Acidification in the Great Smoky Mountains National Park

Episodic stream acidification from atmospheric deposition is suspected to detrimentally impact native southern brook trout (Salvelinus fontinalis) in Great Smoky Mountains National Park (GRSM) headwater streams. To test the hypothesis that episodes of stream acidification cause physiological distress to native trout, caged fish at three sites were exposed to acid episodes during in situ bioassays conducted in June 2006 and March 2007. Stream pH decreased (>0.7 pH units) and total dissolved aluminum (Al(TD)) increased (>175 microg/L) at all three sites during acid episodes in both bioassays. Whole-body sodium concentrations were significantly reduced (10-20%) following the acid episodes, when preceding 24-h mean pH values of 4.88, 5.09, and 4.87 and corresponding 24-h time-weighted average Al(TD) concentrations of 210, 202, and 202 microg/L were observed. Lower whole-body sodium concentrations were correlated with elevated H+ and Al(TD) concentrations. Loss of sodium ions in native southern brook trout was consistent with physiological distress resulting from acid exposure reported in salmonids in other investigations. Further research is necessary to conclude whether acid episodes are responsible for extirpation of brook trout from headwater streams in the GRSM.

Whole‐body sodium concentration in larval fathead minnows (Pimephales promelas) during and following copper exposure

This research used whole-body sodium concentration to characterize exposure and recovery of larval fathead minnows (Pimephales promelas) from acute pulsed copper exposures. Whole-body sodium was chosen because the acute mechanism of copper toxicity to fishes is putative disruption of ion regulation, resulting in a loss of sodium and eventually leading to mortality. Whole-body sodium response in larval fathead minnows exposed to copper was both concentration and duration dependent. The loss of sodium to approximately 70% of control levels occurred within 12 h of exposure. Organisms demonstrated an ability to recover whole-body sodium within 48 h after exposure to concentrations below 0.47 microM Cu2+ for 3, 6, or 9 h. However, at higher concentrations, organisms required more than 48 h to recover. Whole-body sodium concentrations and mortality for all continuous exposures were strongly correlated. These results may facilitate development of a physiologically based model to predict the response of organisms to copper in receiving streams.

Mechanism of acute silver toxicity in Daphnia magna

Daphnids (Daphnia magna) were exposed to AgNO3 at 0.303 +/- 0.017 microg silver/L (46.9% as Ag+), in the absence of food, in moderately hard synthetic water under static conditions for up to 48 h. Results from accumulation experiments demonstrated that silver body burden was inversely related to body mass. Daphnids exposed to silver exhibited ionoregulatory disturbance, which was characterized by decreases in whole-body sodium concentration. This ionoregulatory disturbance was explained, at least in part, by a competitive inhibition of the whole-body sodium uptake (six- to sevenfold increase in the Michaelis constant with no change in maximal velocity), which was complete by 1 h of exposure, and resulted in approximately 40% inhibition of sodium influx from the water. A rapidly developing inhibition of whole-body Na+,K(+)-dependent adenosine triphosphatase (Na+,K(+)-ATPase) activity, significant by 2 h and complete at 90% blockade by 12 h, also was observed during exposure to AgNO3. Therefore, these findings clearly demonstrate that the key mechanism involved in acute Ag+ toxicity in D. magna, the most sensitive freshwater organism tested to date, resembles that described for freshwater fish--that is, inhibition of active sodium uptake by blockade of Na+,K(+)-ATPase. Furthermore, the results showed that Na+,K(+)-ATPase inhibition was directly related to silver accumulation in the whole body of D. magna. However, the nature of the sodium uptake inhibition (competitive vs noncompetitive in fish) and the fact that whole-body chloride concentration was not disturbed in daphnids was different from fish. With regard to the biotic ligand model (BLM) for silver, our results yielded a log K value of about 8.9. However, the current version of the BLM uses a rainbow trout log K value (7.3) but achieves the correct sensitivity of the model for daphnids by reducing the saturation of toxic sites needed to cause toxicity. An alternative way may be to use the log K value derived from the present results.

The Influence of Acidic Runoff Episodes on Slimy Sculpin Reproduction in Stone Run

Abstract Much research has been devoted to the effects of acidic runoff episodes on populations of brook trout Salvelinus fontinalis. Less is known about slimy sculpin Cottus cognatus and why their numbers have declined in acidified streams. Adult tolerance of low pH and aluminum (Al) toxicity is similar in these two species. Slimy sculpin spawn in the spring, when high stream flows elevate concentrations of toxic Al and decrease stream pH in acid-sensitive watersheds. We hypothesized that acidic episodes in spring were a source of stress for slimy sculpin and hindered their reproduction. We tested this hypothesis by examining the mortality, behavior, whole-body sodium concentrations, and spawning among slimy sculpin exposed to ambient conditions during the spring spawning period in two Pennsylvania streams, Stone Run (an episodically acidified stream that formerly contained slimy sculpin) and Benner Run (a stream with slimy sculpin that does not experience severe acidic episodes). Our hypothesis was supp...

Condition factor and whole-body sodium concentrations in a freshwater fish: Evidence for acidification stress and possible ionoregulatory over-compensation

Condition factor, “K”, was measured for 1202 blacknose dace (Rhinichthys atratulus) from three streams in Shenandoah National Park (USA) of different acid neutralizing capacities (ANCs). “K” is a ratio of weight standardized to length; it is an indication of the health of the individuals in a population. R. atratulus condition factor in the low-ANC stream was found to be significantly lower (11%) than that of dace measured for fish from the intermediate- and high-ANC streams. This difference, according to the results of related investigations, is likely to be biologically significant. Whole-body sodium concentrations were measured as an additional test of sublethal stress in these streams. During summer base flow conditions, mean whole-body sodium concentrations of adult R. atratulus maintained in cages were found to be highest in the low-ANC stream and lowest in the high-ANC stream. The lower condition factor of dace in the low-ANC stream may be related to whole-body sodium concentration and ion regulation. Ion regulation in the low-ANC stream may be more metabolically costly because of chronic sublethal pH stress. R. atratulus may maintain high body Na+ concentrations in low ANC- and ionic strength waters in order to provide a buffer against large episodic pH depressions. The metabolic cost of this ionoregulatory over-compensation may necessitate the diversion of energy from somatic growth and explain the poorer condition of fish from such waters.