Excretion and conservation of glycerol, and expression of aquaporins and glyceroporins, during cold acclimation in Cope's gray tree frog Hyla chrysoscelis

2007 ◽  
Vol 292 (1) ◽  
pp. R544-R555 ◽  
Author(s):  
Sarah L. Zimmerman ◽  
James Frisbie ◽  
David L. Goldstein ◽  
Jennifer West ◽  
Kevin Rivera ◽  
...  
Keyword(s):  
Cold Acclimation ◽  
Expression System ◽  
Plasma Concentrations ◽  
Water Channel ◽  
Tree Frog ◽  
Hyla Chrysoscelis ◽  
Water Reabsorption ◽  
Real Time Quantitative Pcr ◽  
Xenopus Oocyte Expression ◽  
Gray Tree Frog

Cope's gray tree frog Hyla chrysoscelis accumulates glycerol during cold acclimation. We hypothesized that, during this process, gray tree frogs adjust renal filtration and/or reabsorption rates to retain accumulated glycerol. During cold acclimation, plasma concentrations of glycerol rose >200-fold, to 51 mmol/l. Although fractional water reabsorption decreased, glomerular filtration rate (GFR) and, consequently, urine flow were <5% of warm levels, and fractional glycerol reabsorption increased. In contrast, dehydrated frogs increased fractional water reabsorption, decreased GFR, and did not accumulate glycerol. We hypothesized that expression of proteins from the aquaporin (AQP)/glyceroporin (GLP) family was associated with changing patterns of water and glycerol movement. We cloned the cDNA for three such proteins, quantified mRNA expression in nine tissues using real-time quantitative PCR, and functionally characterized them using a Xenopus oocyte expression system. HC-1, an AQP1-like water channel conferring low glycerol permeability, is expressed ubiquitously in warm- and cold-acclimated tissues. HC-2, a water channel most similar to AQP2, is primarily expressed in organs of osmoregulation. HC-3, which is most similar to AQP3, is functionally characterized as a GLP, with low permeability to water but high permeability to glycerol. Aspects of expression levels and functional characteristics varied between cold and warm conditions for each of the three AQPs, suggesting a complex pattern of involvement in osmoregulation related to thermal acclimation.

Renal water handling in rats with decompensated liver cirrhosis

2000 ◽  
Vol 279 (6) ◽  
pp. F1101-F1109 ◽  
Author(s):  
Thomas E. N. Jonassen ◽  
Sten Christensen ◽  
Tae-Hwan Kwon ◽  
Susanna Langhoff ◽  
Nanna Salling ◽  
...  
Keyword(s):  
Liver Cirrhosis ◽  
Collecting Duct ◽  
Plasma Concentrations ◽  
Water Channel ◽  
Intraperitoneal Administration ◽  
Plasma Sodium ◽  
Water Reabsorption ◽  
Decompensated Liver Cirrhosis ◽  
Water Excretion ◽  
Urine Production

The present study was performed to investigate the renal handling of water in rats with decompensated liver cirrhosis. Liver cirrhosis was induced by intraperitoneal administration of carbon tetrachloride twice weekly for 16 wk. Control rats were treated with vehicle. The cirrhotic rats developed severe disturbances in water homeostasis: urine production was decreased and hyperosmotic, the rats had significantly decreased plasma sodium concentration and ascites, and the ability to excrete an intravenous water load was significantly impaired. Plasma concentrations of vasopressin and aldosterone were increased. Mean arterial pressure, glomerular filtration rate (GFR), and fractional lithium excretion were decreased. Acute vasopressin type 2-receptor blockade with the selective nonpeptide antagonist OPC-31260 (800 μg · kg−1 · h−1) was performed during conditions whereby volume depletion was prevented by computer-driven, servo-controlled intravenous volume replacement with 150 mM glucose. The aquaretic response to OPC-31260 was similar in cirrhotic and control rats. However, the OPC 31260-induced rises in fractional water excretion (ΔV/GFR; +24%) and fractional distal water excretion (ΔV/CLi; +46%) were significantly increased in the cirrhotic rats, where V is flow rate and Δ is change. This suggests that vasopressin-mediated renal water reabsorption capacity was increased in the cirrhotic rats. Semiquantitative immunoblotting revealed that the expression of the vasopressin-regulated water channel aquaporin-2 was unchanged in membrane fractions of both whole kidney and inner medulla from cirrhotic rats. Together, these results suggest a relative escape from vasopressin on collecting duct water reabsorption in rats with decompensated liver cirrhosis.

Isolation and characterization of simple sequence repeat loci in the gray tree frog, Hyla chrysoscelis

Genome ◽  
1999 ◽  
Vol 42 (4) ◽  
pp. 676-680 ◽  
Author(s):  
J.D. Krenz ◽  
R.D. Semlitsch ◽  
H.C. Gerhardt ◽  
P.A. Mahoney
Keyword(s):  
Simple Sequence Repeat ◽  
Tree Frog ◽  
Hyla Chrysoscelis ◽  
Sequence Repeat ◽  
Isolation And Characterization ◽  
Simple Sequence ◽  
Gray Tree Frog

Season and testosterone affect contractile properties of fast calling muscles in the gray tree frog Hyla chrysoscelis

2003 ◽  
Vol 284 (6) ◽  
pp. R1513-R1520 ◽  
Author(s):  
Mahasweta Girgenrath ◽  
Richard L. Marsh
Keyword(s):  
Breeding Season ◽  
Sound Production ◽  
Contractile Properties ◽  
Trunk Muscles ◽  
Tree Frog ◽  
Hyla Chrysoscelis ◽  
Nonbreeding Season ◽  
Secondary Sexual Characteristics ◽  
Sexual Characteristics ◽  
Gray Tree Frog

In anurans, circulating levels of androgens influence certain secondary sexual characteristics that are expressed only during the breeding season. We studied the contractile properties of external oblique muscles (used to power sound production) in a species of North American gray tree frog, Hyla chrysoscelis, during the breeding season and also in testosterone-treated captive males and females after the breeding season. Compared with the muscles of breeding-season males, the trunk muscles of postbreeding-season males have 50% less mass, 60% longer twitches, and 40% slower shortening velocities. Testosterone levels similar to those found in breeding-season male hylid frogs restore the contractile speed and mass of male trunk muscles and also convert the small slow trunk muscles of females into larger fast-contracting muscles. We conclude that androgens likely play a key role in altering the contractile properties of these muscles in males during the annual cycle, allowing them to operate in the breeding season at the frequencies required to produce the characteristic rapidly pulsed calls of this species. Females as well as nonbreeding-season males do not produce advertising calls, and therefore the slower muscles found in these animals may allow more economic operation of these muscles. The effects of testosterone on female trunk muscles indicate the potential of this hormone in contributing to the sexual dimorphism in size and contractile properties of these muscles, but this dimorphism is likely due to the interaction of more than one hormone.

Isolation and characterization of simple sequence repeat loci in the gray tree frog, Hyla chrysoscelis

Genome ◽  
1999 ◽  
Vol 42 (4) ◽  
pp. 676-680 ◽  
Author(s):  
J D Krenz ◽  
R D Semlitsch ◽  
H C Gerhardt ◽  
P A Mahoney
Keyword(s):  
Simple Sequence Repeat ◽  
Large Scale ◽  
Genomic Library ◽  
Tree Frog ◽  
Hyla Chrysoscelis ◽  
Sequence Repeat ◽  
Isolation And Characterization ◽  
Ssr Loci ◽  
Simple Sequence ◽  
Gray Tree Frog

A gray tree frog (Hyla chrysoscelis) genomic library was constructed and characterized with regard to the incidence and complexity of simple sequence repeat (SSR) loci. The partial genomic library, containing approximately 10 000 clones with an average-sized insert of 350 bp, was screened with six SSR repeat oligonucleotides (AC, AG, ACG, AGC, AAC, and AAG). Screening identified 31 unique positive clones containing 41 SSR loci. Sequences of tandemly arrayed dinucleotide repeats were more common (36 of 41) than trinucleotide repeats. Twenty-six loci were identified using the AC dinucleotide probe, while 7 loci were identified using the AG dinucleotide probe. An additional 3 AT dinucleotide loci were serendipitously identified. The AT repeats generally comprised the longest dinucleotide repeat loci. The SSR repeat loci reported here should provide potent markers for identity, parentage, and short-lineage determinations in large-scale experiments using gray tree frogs.Key words: Hyla chrysoscelis, simple sequence repeat, SSR, gray tree frog, microsatellite.

scholarly journals Vasopressin-vermittelte Wasserrückresorption im Sammelrohr der Niere

BIOspektrum ◽  
2021 ◽  
Vol 27 (2) ◽  
pp. 165-167
Author(s):  
Sandrine Baltzer ◽  
Enno Klussmann
Keyword(s):  
Water Balance ◽  
Small Molecules ◽  
High Throughput ◽  
Molecular Mechanisms ◽  
Collecting Duct ◽  
Water Channel ◽  
Water Reabsorption ◽  
Balance Disorders ◽  
Water Homeostasis ◽  
Balance Disorder

AbstractVasopressin-mediated water reabsorption from primary urine in the renal collecting duct is essential for regulating body water homeostasis and depends on the water channel aquaporin-2 (AQP2).Dysregulation of the process can cause water balance disorders. Here, we present cell-based high-throughput screenings to identify proteins and small molecules as tools to elucidate molecular mechanisms underlying the AQP2 control and as potential starting points for the development of water balance disorder drugs.

scholarly journals Specific and Nonspecific Effects of Protein Kinase C on the Epithelial Na + Channel

2000 ◽  
Vol 115 (5) ◽  
pp. 559-570 ◽  
Author(s):  
Mouhamed S. Awayda
Keyword(s):  
Membrane Trafficking ◽  
Expression System ◽  
Na Channel ◽  
Specific Effects ◽  
Nonspecific Effects ◽  
Oocyte Expression ◽  
Xenopus Oocyte Expression ◽  
Oocyte Expression System ◽  
Baseline Values ◽  
Epithelial Na Channel

The Xenopus oocyte expression system was used to explore the mechanisms of inhibition of the cloned rat epithelial Na+ channel (rENaC) by PKC (Awayda, M.S., I.I. Ismailov, B.K. Berdiev, C.M. Fuller, and D.J. Benos. 1996. J. Gen. Physiol. 108:49–65) and to determine whether human ENaC exhibits similar regulation. Effects of PKC activation on membrane and/or channel trafficking were determined using impedance analysis as an indirect measure of membrane area. hENaC-expressing oocytes exhibited an appreciable activation by hyperpolarizing voltages. This activation could be fit with a single exponential, described by a time constant (τ) and a magnitude (ΔI V). A similar but smaller magnitude of activation was also observed in oocytes expressing rENaC. This activation likely corresponds to the previously described effect of hyperpolarizing voltage on gating of the native Na+ channel (Palmer, L.G., and G. Frindt. 1996. J. Gen. Physiol. 107:35–45). Stimulation of PKC with 100 nM PMA decreased ΔIV in hENaC-expressing oocytes to a plateau at 57.1 ± 4.9% (n = 6) of baseline values at 20 min. Similar effects were observed in rENaC-expressing oocytes. PMA decreased the amiloride-sensitive hENaC slope conductance (gNa) to 21.7 ± 7.2% (n = 6) of baseline values at 30 min. This decrease was similar to that previously reported for rENaC. This decrease of g Na was attributed to a decrease of membrane capacitance (C m), as well as the specific conductance (gm/Cm ). The effects on gm/Cm reached a plateau within 15 min, at ∼60% of baseline values. This decrease is likely due to the specific ability of PKC to inhibit ENaC. On the other hand, the decrease of Cm was unrelated to ENaC and is likely an effect of PKC on membrane trafficking, as it was observed in ENaC-expressing as well as control oocytes. At lower PMA concentrations (0.5 nM), smaller changes of Cm were observed in rENaC- and hENaC-expressing oocytes, and were preceded by larger changes of gm and by changes of gm/Cm, indicating specific effects on ENaC. These findings indicate that PKC exhibits multiple and specific effects on ENaC, as well as nonspecific effects on membrane trafficking. Moreover, these findings provide the electrophysiological basis for assessing channel-specific effects of PKC in the Xenopus oocyte expression system.

Regulation of a cloned epithelial Na+ channel by its β- and γ-subunits

1997 ◽  
Vol 273 (6) ◽  
pp. C1889-C1899 ◽  
Author(s):  
Mouhamed S. Awayda ◽  
Albert Tousson ◽  
Dale J. Benos
Keyword(s):  
Fluorescence Intensity ◽  
Expression System ◽  
Fold Increase ◽  
Na Channel ◽  
Β Subunit ◽  
Open Probability ◽  
Animal Pole ◽  
Α Subunit ◽  
Amino Acid Peptide ◽  
Xenopus Oocyte Expression

Using the Xenopus oocyte expression system, we examined the mechanisms by which the β- and γ-subunits of an epithelial Na+channel (ENaC) regulate α-subunit channel activity and the mechanisms by which β-subunit truncations cause ENaC activation. Expression of α-ENaC alone produced small amiloride-sensitive currents (−43 ± 10 nA, n = 7). These currents increased >30-fold with the coexpression of β- and γ-ENaC to −1,476 ± 254 nA ( n = 20). This increase was accompanied by a 3.1- and 2.7-fold increase of membrane fluorescence intensity in the animal and vegetal poles of the oocyte, respectively, with use of an antibody directed against the α-subunit of ENaC. Truncation of the last 75 amino acids of the β-subunit COOH terminus, as found in the original pedigree of individuals with Liddle’s syndrome, caused a 4.4-fold ( n = 17) increase of the amiloride-sensitive currents compared with wild-type αβγ-ENaC. This was accompanied by a 35% increase of animal pole membrane fluorescence intensity. Injection of a 30-amino acid peptide with sequence identity to the COOH terminus of the human β-ENaC significantly reduced the amiloride-sensitive currents by 40–50%. These observations suggest a tonic inhibitory role on the channel’s open probability ( P o) by the COOH terminus of β-ENaC. We conclude that the changes of current observed with coexpression of the β- and γ-subunits or those observed with β-subunit truncation are likely the result of changes of channel density in combination with large changes of P o.

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