Effects of saline acclimation on plasma electrolytes, urea excretion, and hepatic urea biosynthesis in a freshwater stingray, Potamotrygon sp. garman, 1877

Gerst, Jeffery W.; Thorson, Thomas B.

doi:10.1016/0300-9629(77)90446-7

Cited by 46 publications

(20 citation statements)

References 26 publications

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“…Being permanently adapted to freshwater over millions of years, the stenohaline Potamotrygonid stingrays possess low levels of OUC enzymes (Goldstein and Forster, 1971; Nitrogen metabolism in P. motoro Anderson, 1980;Anderson, 1995;Anderson, 2001), and they osmoregulate in a way similar to freshwater teleosts. Hence, unlike marine elasmobranchs, Potamotrygonid stingrays are ammonotelic, excreting the majority of the waste N as ammonia (Goldstein and Forster, 1971;Gerst and Thorson, 1977;Barcellos et al, 1997). They can survive up to 40% seawater in the laboratory (Thorson, 1967;Gerst and Thorson, 1977), but unlike other euryhaline stingrays (Piermarini and Evans, 1998;Tam et al, 2003;Ip et al, 2005), there is no induction of increased urea synthesis and retention (Thorson, 1970) as the expression of CPS III has been suppressed (Gerst and Thorson, 1977).…”

Section: Introductionmentioning

confidence: 99%

“…Hence, unlike marine elasmobranchs, Potamotrygonid stingrays are ammonotelic, excreting the majority of the waste N as ammonia (Goldstein and Forster, 1971;Gerst and Thorson, 1977;Barcellos et al, 1997). They can survive up to 40% seawater in the laboratory (Thorson, 1967;Gerst and Thorson, 1977), but unlike other euryhaline stingrays (Piermarini and Evans, 1998;Tam et al, 2003;Ip et al, 2005), there is no induction of increased urea synthesis and retention (Thorson, 1970) as the expression of CPS III has been suppressed (Gerst and Thorson, 1977). Interestingly, their plasma [Na + ] and [Cl -] increase with the ambient salinity (Bittner and Lang, 1980;Gerst and Thorson, 1977).…”

Section: Introductionmentioning

confidence: 99%

“…They can survive up to 40% seawater in the laboratory (Thorson, 1967;Gerst and Thorson, 1977), but unlike other euryhaline stingrays (Piermarini and Evans, 1998;Tam et al, 2003;Ip et al, 2005), there is no induction of increased urea synthesis and retention (Thorson, 1970) as the expression of CPS III has been suppressed (Gerst and Thorson, 1977). Interestingly, their plasma [Na + ] and [Cl -] increase with the ambient salinity (Bittner and Lang, 1980;Gerst and Thorson, 1977). However, to date, no information is available on how tissues of Potamotrygonid stingrays respond to increased plasma ionic concentrations.…”

Section: Introductionmentioning

confidence: 99%

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The freshwater Amazonian stingray, Potamotrygon motoro, up-regulates glutamine synthetase activity and protein abundance, and accumulates glutamine when exposed to brackish (15‰) water

Loong

Ching

et al. 2009

Journal of Experimental Biology

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SUMMARYThis study aimed to examine whether the stenohaline freshwater stingray, Potamotrygon motoro, which lacks a functional ornithine-urea cycle, would up-regulate glutamine synthetase (GS) activity and protein abundance, and accumulate glutamine during a progressive transfer from freshwater to brackish (15‰) water with daily feeding. Our results revealed that, similar to other freshwater teleosts, P. motoro performed hyperosmotic regulation, with very low urea concentrations in plasma and tissues, in freshwater. In 15‰ water, it was non-ureotelic and non-ureoosmotic, acting mainly as an osmoconformer with its plasma osmolality, [Na + ] and [Cl -] comparable to those of the external medium. There were significant increases in the content of several free amino acids (FAAs), including glutamate, glutamine and glycine, in muscle and liver, but not in plasma, indicating that FAAs could contribute in part to cell volume regulation. Furthermore, exposure of P. motoro to 15‰ water led to up-regulation of GS activity and protein abundance in both liver and muscle. Thus, our results indicate for the first time that, despite the inability to synthesize urea and the lack of functional carbamoyl phosphate synthetase III (CPS III) which uses glutamine as a substrate, P. motoro retained the capacity to up-regulate the activity and protein expression of GS in response to salinity stress. Potamotrygon motoro was not nitrogen (N) limited when exposed to 15‰ water with feeding, and there were no significant changes in the amination and deamination activities of hepatic glutamate dehydrogenase. In contrast, P. motoro became N limited when exposed to 10‰ water with fasting and could not survive well in 15‰ water without food.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The freshwater Amazonian stingray, Potamotrygon motoro, up-regulates glutamine synthetase activity and protein abundance, and accumulates glutamine when exposed to brackish (15‰) water

Loong

Ching

et al. 2009

Journal of Experimental Biology

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“…urea and trimethylamine oxide) and reduced size of their salt-secreting rectal gland compared with marine elasmobranchs (Thorson et al 1967, 1978, Thorson 1970, Gerst & Thorson 1977. Because they obviously face very different ionoregulatory problems than marine elasmobranchs, Potamotrygonid rays are excellent comparative models relative to euryhaline species such as D. sabina.…”

Section: Introductionmentioning

confidence: 99%

“…Because they obviously face very different ionoregulatory problems than marine elasmobranchs, Potamotrygonid rays are excellent comparative models relative to euryhaline species such as D. sabina. Indeed, there is a growing body of literature regarding ionoregulation in these animals (for example, see Thorson 1970, Carrier & Evans 1973, Gerst & Thorson 1977, Wood et al 2002. The goals of the current investigation were to isolate and characterize cDNA clones encoding StAR from the interrenal glands of freshwater stingrays (Potamotrygon hystrix and P. motoro) because of the importance of StAR to the regulated synthesis of corticosteriods that are involved in elasmobranch ionoregulation and other homeostatic processes (e.g.…”

Section: Introductionmentioning

confidence: 99%

Cloning and characterization of cDNAs encoding steroidogenic acute regulatory protein from freshwater stingrays (Potamotrygon spp.)

Nunez¹,

Piermarini²,

Evans³

et al. 2005

Journal of Molecular Endocrinology

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The steroidogenic acute regulatory protein (StAR) is critical to the regulated synthesis of steroids in vertebrates. We have isolated cDNA sequences encoding StAR in the freshwater stingrays Potamotrygon hystrix and P. motoro. A single P. hystrix StAR transcript (3376 bp) and two overlapping P. motoro StAR transcripts (1272 and 3365 bp) were isolated. The P. hystrix and P. motoro StAR transcripts contain open reading frames encoding proteins of 284 amino acids that are 99% identical to each other and 56-64% identical to other StAR proteins. Pregnenolone synthesis by green monkey kidney (COS-1) cells transfected with an expression construct encoding a human cholesterol side chain cleavage/adrenodoxin reductase/adrenodoxin fusion protein was increased 16-fold by coexpression with a pCMV5/P. motoro StAR expression construct. Northern blot analysis revealed a single 4000 bp StAR transcript in the P. motoro interrenal gland, but RT-PCR indicates StAR mRNA is also expressed in the brain, gonads, atria, ventricle, gill (female only) and muscle (female only). Expression in extragonadal and extraadrenocortical tissues is an indication that StAR may be critical to processes other than steroidogenesis. The longest P. motoro StAR transcript contains a sequence with great similarity to short interspersed repetitive elements found in other elasmobranchs. This study is the first to isolate and characterize elasmobranch StAR cDNA sequences and to demonstrate the activity of a nonmammalian StAR protein in a heterologous expression system.

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Osmoregulation and Excretion

Larsen

Deaton

Onken

et al. 2014

Comprehensive Physiology

185

141

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The article discusses advances in osmoregulation and excretion with emphasis on how multicellular animals in different osmotic environments regulate their milieu intérieur. Mechanisms of energy transformations in animal osmoregulation are dealt with in biophysical terms with respect to water and ion exchange across biological membranes and coupling of ion and water fluxes across epithelia. The discussion of functions is based on a comparative approach analyzing mechanisms that have evolved in different taxonomic groups at biochemical, cellular and tissue levels and their integration in maintaining whole body water and ion homeostasis. The focus is on recent studies of adaptations and newly discovered mechanisms of acclimatization during transitions of animals between different osmotic environments. Special attention is paid to hypotheses about the diversity of cellular organization of osmoregulatory and excretory organs such as glomerular kidneys, antennal glands, Malpighian tubules and insect gut, gills, integument and intestine, with accounts on experimental approaches and methods applied in the studies. It is demonstrated how knowledge in these areas of comparative physiology has expanded considerably during the last two decades, bridging seminal classical works with studies based on new approaches at all levels of anatomical and functional organization. A number of as yet partially unanswered questions are emphasized, some of which are about how water and solute exchange mechanisms at lower levels are integrated for regulating whole body extracellular water volume and ion homeostasis of animals in their natural habitats. © 2014 American Physiological Society.

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Effects of saline acclimation on plasma electrolytes, urea excretion, and hepatic urea biosynthesis in a freshwater stingray, Potamotrygon sp. garman, 1877

Cited by 46 publications

References 26 publications

The freshwater Amazonian stingray, Potamotrygon motoro, up-regulates glutamine synthetase activity and protein abundance, and accumulates glutamine when exposed to brackish (15‰) water

The freshwater Amazonian stingray, Potamotrygon motoro, up-regulates glutamine synthetase activity and protein abundance, and accumulates glutamine when exposed to brackish (15‰) water

Cloning and characterization of cDNAs encoding steroidogenic acute regulatory protein from freshwater stingrays (Potamotrygon spp.)

Osmoregulation and Excretion

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