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NASA NTRS2003

Vapor Pressure, Vapor Composition and Fractional Vaporization of High Temperature Lavas on Io

Observations show that Io's atmosphere is dominated by SO2 and other sulfur and sulfur oxide species, with minor amounts of Na, K, and Cl gases. Theoretical modeling and recent observations show that NaCl, which is produced volcanically, is a constituent of the atmosphere. Recent Galileo, HST and ground-based observations show that some volcanic hot spots on Io have extremely high temperatures, in the range 1400-1900 K. At similar temperatures in laboratory experiments, molten silicates and oxides have significant vapor pressures of Na, K, SiO, Fe, Mg, and other gases. Thus vaporization of these species from high temperature lavas on Io seems likely. We therefore modeled the vaporization of silicate and oxide lavas suggested for Io. Our results for vapor chemistry are reported here. The effects of fractional vaporization on lava chemistry are given in a companion abstract by Kargel et al.

Fegley, B., Jr.↗

NASA NTRS2003

Meter-Scale 3-D Models of the Martian Surface from Combining MOC and MOLA Data

We have extended our previous efforts to derive through controlled photoclinometry, accurate, calibrated, high-resolution topographic models of the martian surface. The process involves combining MGS MOLA topographic profiles and MGS MOC Narrow Angle images. The earlier work utilized, along with a particular MOC NA image, the MOLA topographic profile that was acquired simultaneously, in order to derive photometric and scattering properties of the surface and atmosphere so as to force the low spatial frequencies of a one-dimensional MOC photoclinometric model to match the MOLA profile. Both that work and the new results reported here depend heavily on successful efforts to: 1) refine the radiometric calibration of MOC NA; 2) register the MOC to MOLA coordinate systems and refine the pointing; and 3) provide the ability to project into a common coordinate system, simultaneously acquired MOC and MOLA with a single set of SPICE kernels utilizing the USGS ISIS cartographic image processing tools. The approach described in this paper extends the MOC-MOLA integration and cross-calibration procedures from one-dimensional profiles to full two-dimensional photoclinometry and image simulations. Included are methods to account for low-frequency albedo variations within the scene.

Soderblom, Laurence A.↗

NASA NTRS2004

Radiolytic Model for Chemical Composition of Europa's Atmosphere and Surface

The overall objective of the present effort is to produce models for major and selected minor components of Europa s neutral atmosphere in 1-D versus altitude and in 2-D versus altitude and longitude or latitude. A 3-D model versus all three coordinates (alt, long, lat) will be studied but development on this is at present limited by computing facilities available to the investigation team. In this first year we have focused on 1-D modeling with Co-I Valery Shematovich s Direct Simulation Monte Carlo (DSMC) code for water group species (H2O, O2, O, OH) and on 2-D with Co-I Mau Wong's version of a similar code for O2, O, CO, CO2, and Na. Surface source rates of H2O and O2 from sputtering and radiolysis are used in the 1-D model, while observations for CO2 at the Europa surface and Na detected in a neutral cloud ejected from Europa are used, along with the O2 sputtering rate, to constrain source rates in the 2-D version. With these separate approaches we are investigating a range of processes important to eventual implementation of a comprehensive 3-D atmospheric model which could be used to understand present observations and develop science requirements for future observations, e.g. from Earth and in Europa orbit. Within the second year we expect to merge the full water group calculations into the 2-D version of the DSMC code which can then be extended to 3-D, pending availability of computing resources. Another important goal in the second year would be the inclusion of sulk and its more volatile oxides (SO, SO2).

Cooper, John F.↗

NASA NTRS2004

Magnetic and Langmuir Probe Measurements on the Plasmoid Thruster Experiment (PTX)

The Plasmoid Thruster Experiment (PTX) operates by inductively producing plasmoids in a conical theta-pinch coil and ejecting them at high velocity. A plasmoid is a plasma with an imbedded closed magnetic field structure. The shape and magnetic field structure of the translating plasmoids have been measured with of an array of magnetic field probes. Six sets of two B-dot probes were constructed for measuring B(sub z) and B(sub theta), the axial and azimuthal components of the magnetic field. The probes are wound on a square G10 form, and have an average (calibrated) NA of 9.37 x l0(exp -5) square meters, where N is the number of turns and A is the cross-sectional area. The probes were calibrated with a Helmholtz coil, driven by a high-voltage pulser to measure NA, and by a signal generator to determine the probe's frequency response. The plasmoid electron number density n(sub e) electron temperature T(sub e), and velocity ratio v/c(sub m), (where v is the bulk plasma flow velocity and c(sub m), is the ion thermal speed) have also been measured with a quadruple Langmuir probe. The Langmuir probe tips are 10 mm long, 20-mil diameter stainless steel wire, housed in a 6-inch long 4-bore aluminum rod. Measurements on PTX with argon and hydrogen from the magnetic field probes and quadruple Langmuir probe will be presented in this paper.

Koelfgen, Syri J.↗

NASA NTRS2003

Investigation of electrolyte measurement in diluted whole blood using spectroscopic and chemometric methods

The feasibility of using near-infrared (NIR) spectroscopy in combination with partial least-squares (PLS) regression was explored to measure electrolyte concentration in whole blood samples. Spectra were collected from diluted blood samples containing randomized, clinically relevant concentrations of Na+, K+, and Ca2+. Sodium was also studied in lysed blood. Reference measurements were made from the same samples using a standard clinical chemistry instrument. Partial least squares (PLS) was used to develop calibration models for each ion with acceptable results (Na+, R2 = 0.86, CVSEP = 9.5 mmol/L; K+, R2 = 0.54, CVSEP = 1.4 mmol/L; Ca2+, R2 = 0.56, CVSEP = 0.18 mmol/L). Slightly improved results were obtained using a narrower wavelength region (470-925 nm) where hemoglobin, but not water, absorbed indicating that ionic interaction with hemoglobin is as effective as water in causing measurable spectral variation. Good models were also achieved for sodium in lysed blood, illustrating that cell swelling, which is correlated with sodium concentration, is not required for calibration model development.

Non-NASA Center↗

NASA NTRS2003

Acutely elevated vasopressin increases circulating concentrations of cortisol and aldosterone in fasting northern elephant seal (Mirounga angustirostris) pups

The physiological actions of vasopressin (VP) in marine mammals are not well defined. To help elucidate its hormonal and renal effects in this group of mammals, northern elephant seal (Mirounga angustirostris) pups (N=7; 99+/-4 kg) were first infused with 0.9% saline (control; 220 ml), followed 24 h later with VP (as a 20 ng kg(-1) bolus, then 2 ng kg(-1) min(-1) for approximately 35 min in 225+/-16 ml saline). During both control and VP periods, blood samples were collected prior to infusion, and 15, 30, 60, 120 min and 24 h after infusion to examine the hormonal responses of the pups to VP. Renal responses were quantified from 24 h urine samples obtained prior to infusion (control) and 24 h post-infusion. Compared to the control period, infusion of VP increased plasma concentrations of cortisol over a 120 min period and aldosterone over 30 min, while plasma renin activity (PRA) was decreased for a 120 min period. The plasma urea:creatinine ratio was elevated following infusion of VP. Urine output and osmotic clearance were increased by 69+/-18% (mean +/- S.E.M.) and 36+/-10%, respectively, but free water clearance and glomerular filtration rate were not significantly altered 24 h post-infusion of VP. Solute (osmolality, Na(+), K(+) and Cl(-)) excretion and fractional excretion of electrolytes were also increased when compared to control values. The increase in cortisol concentration suggests that VP may possess corticotropin releasing hormone-like activity in elephant seals. If osmotic diuresis and natriuresis are typical consequences of elevated [VP] in fasting pups, then not increasing VP normally during the fast may serve as a protective mechanism to avoid the potential loss of Na(+) induced by elevated [VP]. Therefore, under natural fasting conditions, pups may be highly sensitive to small changes in [VP], resulting in the maintenance of water and electrolyte balance.

Non-NASA Center↗

NASA NTRS2002

NRSF causes cAMP-sensitive suppression of sodium current in cultured hippocampal neurons

The neuron restrictive silencer factor (NRSF/REST) has been shown to bind to the promoters of many neuron-specific genes and is able to suppress transcription of Na(+) channels in PC12 cells, although its functional effect in terminally differentiated neurons is unknown. We constructed lentiviral vectors to express NRSF as a bicistronic message with green fluorescent protein (GFP) and followed infected hippocampal neurons in culture over a period of 1-2 wk. NRSF-expressing neurons showed a time-dependent suppression of Na(+) channel function as measured by whole cell electrophysiology. Suppression was reversed or prevented by the addition of membrane-permeable cAMP analogues and enhanced by cAMP antagonists but not affected by increasing protein expression with a viral enhancer. Secondary effects, including altered sensitivity to glutamate and GABA and reduced outward K(+) currents, were duplicated by culturing GFP-infected control neurons in TTX. The striking similarity of the phenotypes makes NRSF potentially useful as a genetic "silencer" and also suggests avenues of further exploration that may elucidate the transcription factor's in vivo role in neuronal plasticity.

Hippocampus/cytology/metabolism↗

NASA NTRS2002

Renal effects of fresh water-induced hypo-osmolality in a marine adapted seal

With few exceptions, marine mammals are not exposed to fresh water; however quantifying the endocrine and renal responses of a marine-adapted mammal to the infusion of fresh water could provide insight on the evolutionary adaptation of kidney function and on the renal capabilities of these mammals. Therefore, renal function and hormonal changes associated with fresh water-induced diuresis were examined in four, fasting northern elephant seal ( Mirounga angustirostris) (NES) pups. A series of plasma samples and 24-h urine voids were collected prior to (control) and after the infusion of water. Water infusion resulted in an osmotic diuresis associated with an increase in glomerular filtration rate (GFR), but not an increase in free water clearance. The increase in excreted urea accounted for 96% of the increase in osmotic excretion. Following infusion of fresh water, plasma osmolality and renin activity decreased, while plasma aldosterone increased. Although primary regulators of aldosterone release (Na(+), K(+) and angiotensin II) were not significantly altered in the appropriate directions to individually stimulate aldosterone secretion, increased aldosterone may have resulted from multiple, non-significant changes acting in concert. Aldosterone release may also be hypersensitive to slight reductions in plasma Na(+), which may be an adaptive mechanism in a species not known to drink seawater. Excreted aldosterone and urea were correlated suggesting aldosterone may regulate urea excretion during hypo-osmotic conditions in NES pups. Urea excretion appears to be a significant mechanism by which NES pups sustain electrolyte resorption during conditions that can negatively affect ionic homeostasis such as prolonged fasting.

NASA Center ARC↗

NASA NTRS2000

Geology and geochemistry of paleosols developed on the Hekpoort Basalt, Pretoria Group, South Africa

The Hekpoort paleosols comprise a regional paleoweathering horizon developed on 2.224 +/- 0.021 Ga basaltic andesite lavas at the top of the Hekpoort Formation of the Pretoria Group, Transvaal Supergroup, South Africa. In five separate profiles, from outcrops along road cuts near Waterval Onder and the Daspoort Tunnel and in three drill cores from the Bank Break Area (BB3, BB8, and BB14), the top of the paleosol is a sericite-rich zone. The sericite zone grades downward into a chlorite-rich zone. In core BB8 and in the road cut at the Daspoort Tunnel, we sampled the underlying or parent basaltic andesite into which the chlorite zone grades. We did not obtain samples of the parent material at Waterval Onder and in cores BB3 and BB14, but chemical analyses indicate that the chlorite and sericite zones in these profiles derive from underlying lavas similar to the ones we sampled in core BB8 and at the Daspoort Tunnel. The presence of apparent rip-up clasts of the paleosol in the overlying ironstones of the Strubenkop Formation in the cores from Bank Break makes it very unlikely that most of the alteration was a result of interactions with hydrothermal fluids. Desiccation cracks at the top of the paleosol that were filled with sand during the deposition of the overlying sediments at Waterval Onder point to a subaerial weathering origin. Very little, if any, Al, Ti, Zr, V, or Cr moved a discernible distance during weathering of any of the five profiles. The vertical distribution of Fe, Mg, Mn, Ni, and Co indicates that these elements were largely removed from the top of the soil during weathering. The overall abundance of these elements in each of the profiles indicates that a significant fraction of the complement lost from the top subsequently reprecipitated in the lower portion of the soil as constituents of an Fe2(+) -rich smectite. The loss of Fe from the top of the soil during weathering of the Hekpoort paleosols indicates that atmospheric PO2 was less than 8 x 10(-4) atm about 2.22 Ga. Fe2(+) -rich smectite should only precipitate during soil formation if atmospheric PCO2 is less than or equal to 2 x 10(-2) atm (Rye, Kuo, and Holland, 1995). Ca and Na were largely lost during weathering. Some Na was apparently added to the sericite zone in cores BB3, BB8, and BB14 after weathering. All five profiles are enriched in K and Rb, and most are enriched in Ba. The distribution of these elements indicates that they all were added during post-weathering hydrothermal metasomatism. Rb-Sr analysis of the paleosol at the Daspoort Tunnel indicates that metasomatism last affected that profile 1.925 +/- 0.032 Ga (Macfarlane and Holland, 1991).

Non-NASA Center↗

NASA NTRS1998

Optimizing the calcium content of a copolymer acrylamide gel matrix for dark-grown seedlings

A copolymer acrylamide acrylate gel was investigated as the sole root matrix for dark-grown seedlings of soybean (Glycine max Merr. 'Century 84'). Increasing Ca2+ in the hydrating solution of the hydrogel from 1 to 10 mM decreased its water-holding capacity from 97 to 46 mL g-1, yet water potential of the medium remained high, sufficient for normal plant growth at all Ca2+ concentrations tested. Elongation rate of dark-grown soybean seedlings over a 54-hour period was 0.9, 1.5, and 1.8 mm h-1 with 1.0, 2.5, or 5.0 mM Ca2+, respectively, but did not increase with further increases in Ca2+ concentration. Further study revealed that Na+ was released from the hydrogel medium and was taken up by the seedlings as Ca2+ increased in the medium. In dry hypocotyl tissue, sodium content correlated negatively with calcium content. Despite the presence of Na+ in the hydrogel, seedling growth was normal when adequate Ca2+ was added in the hydrating solution. Acrylamide hydrogels hold good potential as a sole growth matrix for short-term experiments with dark-grown seedlings without irrigation.

NASA Discipline Plant Biology↗

NASA NTRS1997

Pre-exercise hypervolemia and cycle ergometer endurance in men

Time to exhaustion at 87-91% of peak VO2 was measured in 5 untrained men (age: 31 +/- 8 years, body mass: 74.20 +/- 16.50 kg, body surface area: 1.90 +/- 0.24 m2, peak VO2: 2.87 +/- 0.40 l min-1, plasma volume: 3.21 +/- 0.88 l; means +/-SD) after consuming nothing (N) or two fluid formulations (10 ml kg-1, 743 +/- 161 ml): Performance 1 (P1), a multi-ionic carbohydrate drink, containing 55 mEq l-1 Na+, 4.16 g l-1 citrate, 20.49 g l-1 glucose, and 365 mOsm kg-1 H2O, and AstroAde (AA), a sodium chloride-sodium citrate hyperhydration drink, containing 164 mEq l-1 Na+, 8.54 g l-1 citrate, <5 mg l-1 glucose, and 253 mOsm kg-1 H2O. Mean (+/-SE) endurance for N, P1 and AA was 24.68 +/- 1.50, 24.55 +/- 1.09, and 30.50 +/- 3.44 min respectively. Percent changes in plasma volume (PV) from -105 min of rest to zero min before exercise were -1.5 +/- 3.2% (N), 0.2 +/- 2.2% (P1), and 4.8 +/- 3.0% (AA; P < 0.05). The attenuated endurance for N and P1 could not be attributed to differences in exercise metabolism (VE, RE, VO2) from the carbohydrate or citrate, terminal heart rate, levels of perceived exertion, forehead or thigh skin blood flow velocity, changes or absolute termination levels of rectal temperature. Thus, the higher level of resting PV for AA just before exercise, as well as greater acid buffering and possible increased energy substrate from citrate, may have contributed to the greater endurance.

NASA Center ARC↗

NASA NTRS1993

Montmorillonite catalysis of RNA oligomer formation in aqueous solution. A model for the prebiotic formation of RNA

Oligomers of adenylic acid of up to the 11-mer in length are formed by the reaction of the phosphorimidazolide of adenosine (ImpA) in pH 8 aqueous solution at room temperature in the presence of Na(+)-montmorillonite. These oligomers are joined by phosphodiester bonds in which the 3',5'-linkage predominates over the 2',5'-linkage by a 2:1 ratio. Reaction of a 9:1 mixture of ImpA, A5'ppA results in the formation of oligomers with a 3:1 ratio of 3',5'- to 2',5'-linked phosphodiester bonds. A high proportion of these oligomers contain the A5'ppA grouping. A5'ppA reacts much more rapidly with ImpA than does 5'-ADP (ppA) or 5'-ATP (pppA). The exchangeable cation associated with the montmorillonite effects the observed catalysis with Li+, Na+, NH4+, and Ca2+ being the more effective while Mg2+ and Al3+ are almost ineffective catalysts. 2',5'-Linked oligomers, up to the tetramer in length, are formed using UO2(2+)-montmorillonite. The structure analysis of individual oligomer fractions was performed by selective enzymatic and KOH hydrolytic studies followed by HPLC analysis of the reaction products. It is concluded from the composition of the oligomers that the rate of addition ImpA to a 3'-terminus containing a 2',5'-linkage is slower than the addition to a nucleoside joined by a 3',5'-linked phosphodiester bond. The potential importance of mineral catalysis of the formation of RNA and other oligomers on primitive Earth is discussed.

Non-NASA Center↗

NASA NTRS2001

Evidence for a role in growth and salt resistance of a plasma membrane H+-ATPase in the root endodermis

The plasma membrane of plant cells is energized by an electrochemical gradient produced by P-type H+-ATPases (proton pumps). These pumps are encoded by at least 12 genes in Arabidopsis. Here we provide evidence that isoform AHA4 contributes to solute transport through the root endodermis. AHA4 is expressed most strongly in the root endodermis and flowers, as suggested by promoter-GUS reporter assays. A disruption of this pump (aha4-1) was identified as a T-DNA insertion in the middle of the gene (after VFP(574)). Truncated aha4-1 transcripts accumulate to approximately 50% of the level observed for AHA4 mRNA in wild-type plants. Plants homozygous for aha4-1 (-/-) show a subtle reduction in root and shoot growth compared with wild-type plants when grown under normal conditions. However, a mutant phenotype is very clear in plants grown under salt stress (e.g., 75 or 110 mM NaCl). In leaves of mutant plants subjected to Na stress, the ratio of Na to K increased 4-5-fold. Interestingly, the aha4-1 mutation appears to be semidominant and was only partially complemented by the introduction of additional wild-type copies of AHA4. These results are consistent with the hypothesis that aha4-1 may produce a dominant negative protein or RNA that partially disrupts the activity of other pumps or functions in the root endodermal tissue, thereby compromising the function of this cell layer in controlling ion homeostasis and nutrient transport.

NASA Discipline Plant Biology↗

NASA NTRS2001

Model study of ATP and ADP buffering, transport of Ca(2+) and Mg(2+), and regulation of ion pumps in ventricular myocyte

We extended the model of the ventricular myocyte by Winslow et al. (Circ. Res 1999, 84:571-586) by incorporating equations for Ca(2+) and Mg(2+) buffering and transport by ATP and ADP and equations for MgATP regulation of ion transporters (Na(+)-K(+) pump, sarcolemmal and sarcoplasmic Ca(2+) pumps). The results indicate that, under normal conditions, Ca(2+) binding by low-affinity ATP and diffusion of CaATP may affect the amplitude and time course of intracellular Ca(2+) signals. The model also suggests that a fall in ATP/ADP ratio significantly reduces sarcoplasmic Ca(2+) content, increases diastolic Ca(2+), lowers systolic Ca(2+), increases Ca(2+) influx through L-type channels, and decreases the efficiency of the Na(+)/Ca(2+) exchanger in extruding Ca(2+) during periodic voltage-clamp stimulation. The analysis suggests that the most important reason for these changes during metabolic inhibition is the down-regulation of the sarcoplasmic Ca(2+)-ATPase pump by reduced diastolic MgATP levels. High Ca(2+) concentrations developed near the membrane might have a greater influence on Mg(2+), ATP, and ADP concentrations than that of the lower Ca(2+) concentrations in the bulk myoplasm. The model predictions are in general agreement with experimental observations measured under normal and pathological conditions.

NASA Discipline Cardiopulmonary↗

NASA NTRS2001

Osmoregulation in marine mammals

Osmoregulation in marine mammals has been investigated for over a century; however, a review of recent advances in our understanding of water and electrolyte balance and of renal function in marine mammals is warranted. The following topics are discussed: (i) kidney structure and urine concentrating ability, (ii) sources of water, (iii) the effects of feeding, fasting and diving, (iv) the renal responses to infusions of varying salinity and (v) hormonal regulation. The kidneys of pinnipeds and cetaceans are reniculate in structure, unlike those of terrestrial mammals (except bears), but this difference does not confer any greater concentrating ability. Pinnipeds, cetaceans, manatees and sea otters can concentrate their urine above the concentration of sea water, but only pinnipeds and otters have been shown to produce urine concentrations of Na+ and Cl- that are similar to those in sea water. This could afford them the capacity to drink sea water and not lose fresh water. However, with few exceptions, drinking is not a common behavior in pinnipeds and cetaceans. Water balance is maintained in these animals via metabolic and dietary water, while incidental ingestion and dietary salt may help maintain electrolyte homeostasis. Unlike most other aquatic mammals, sea otters commonly drink sea water and manatees frequently drink fresh water. Among the various taxonomic groups of marine mammals, the sensitivity of the renin-angiotensin-aldosterone system appears to be influenced by the availability of Na+. The antidiuretic role of vasopressin remains inconclusive in marine mammals, while the natriuretic function of atrial natriuretic peptide has yet to be examined. Ideas on the direction of future studies are presented.

Non-NASA Center↗

NASA NTRS2000

Effects of acute fresh water exposure on water flux rates and osmotic responses in Kemp's ridley sea turtles (Lepidochelys kempi)

Water flux rates and osmotic responses of Kemp's Ridley sea turtles (Lepidochelys kempi) acutely exposed to fresh water were quantified. Salt-water adapted turtles were exposed to fresh water for 4 d before being returned to salt water. During the initial salt water phase, absolute and relative water flux rates were 1.2+/-0.1 l d(-1) and 123.0+/-6.8 ml kg(-1) d(-1), respectively. When turtles were exposed to fresh water, rates increased by approximately 30%. Upon return to salt water, rates decreased to original levels. Plasma osmolality, Na(+), K(+), and Cl(-) decreased during exposure to fresh water, and subsequently increased during the return to salt water. The Na(+):K(+) ratio was elevated during the fresh water phase and subsequently decreased upon return to salt water. Aldosterone and corticosterone were not altered during exposure to fresh water. Elevated water flux rates during fresh water exposure reflected an increase in water consumption, resulting in a decrease in ionic and osmotic concentrations. The lack of a change in adrenocorticoids to acute fresh water exposure suggests that adrenal responsiveness to an hypo-osmotic environment may be delayed in marine turtles when compared to marine mammals.

Non-programmatic↗

NASA NTRS2000

Effect of hyperosmotic solutions on salt excretion and thirst in rats

We investigated urinary changes and thirst induced by infusion of hyperosmotic solutions in freely moving rats. Intracarotid infusions of 0.3 M NaCl (4 ml/20 min, split between both internal carotid arteries) caused a larger increase in excretion of Na(+) and K(+) than intravenous infusions, indicating that cephalic sensors were involved in the response to intracarotid infusions. Intravenous and intracarotid infusions of hyperosmotic glycerol or urea (300 mM in 150 mM NaCl) had little or no effect, suggesting the sensors were outside the blood-brain barrier (BBB). Intracarotid infusion of hypertonic mannitol (300 mM in 150 mM NaCl) was more effective than intravenous infusion, suggesting that cell volume rather than Na(+) concentration of the blood was critical. Similarly, intracarotid infusion (2 ml/20 min, split between both sides), but not intravenous infusion of hypertonic NaCl or mannitol caused thirst. Hyperosmotic glycerol, infused intravenously or into the carotid arteries, did not cause thirst. We conclude that both thirst and electrolyte excretion depend on a cell volume sensor that is located in the head, but outside the BBB.

NASA Discipline Regulatory Physiology↗

NASA NTRS1998

Alteration of renal function of rats following spaceflight

Following spaceflight, changes in renal function of humans have been suggested. To assess the effects of readaptation on renal function, urine was collected from male rats ( approximately 245 g) over a 2-wk period following a 14-day spaceflight. Rats were assigned to three groups: flight animals (n = 6), flight controls (n = 6) housed in the flight cages on the ground, and vivarium controls (n = 5) housed in standard shoe box cages. Animals were placed into individual metabolic cages for urine collection. Urine output was significantly increased for 3 days following flight. Excretion rates of Na+ and K+ were increased, resulting in an increased osmotic excretion rate. Creatinine excretion rate increased over the first two postflight days. Glomerular filtration rate increased immediately following spaceflight without changes in plasma creatinine, Na+, K+, or osmolality. Increased excretion of solute was thus the result of increased delivery and a decreased percent reabsorption of the filtered load. Osmolal clearance was increased immediately postflight while free water clearance was decreased. In growing rats, the diuresis after short-duration spaceflight is the result of an increase in solute excretion with an accompanying reduction in free water clearance.

STS-58 Shuttle Project↗