Development of Na+, K+ ATPase enzyme activity and expression patterns of sulfate transporters in gills, intestine and kidney during smoltification and SW acclimation in Atlantic salmon (Salmo salar L.)

Postponed access: the file will be accessible after 2021-06-03Masteroppgave i biologiBIO399MAMN-BI

Role of the kidneys in acid-base regulation and ammonia excretion in freshwater and seawater fish: implications for nephrocalcinosis

Maintaining normal pH levels in the body fluids is essential for homeostasis and represents one of the most tightly regulated physiological processes among vertebrates. Fish are generally ammoniotelic and inhabit diverse aquatic environments that present many respiratory, acidifying, alkalinizing, ionic and osmotic stressors to which they are able to adapt. They have evolved flexible strategies for the regulation of acid-base equivalents (H+, NH4+, OH− and HCO3−), ammonia and phosphate to cope with these stressors. The gills are the main regulatory organ, while the kidneys play an important, often overlooked accessory role in acid-base regulation. Here we outline the kidneys role in regulation of acid-base equivalents and two of the key ‘urinary buffers’, ammonia and phosphate, by integrating known aspects of renal physiology with recent advances in the molecular and cellular physiology of membrane transport systems in the teleost kidneys. The renal transporters (NHE3, NBC1, AE1, SLC26A6) and enzymes (V-type H+ATPase, CAc, CA IV, ammoniagenic enzymes) involved in H+ secretion, bicarbonate reabsorption, and the net excretion of acidic and basic equivalents, ammonia, and inorganic phosphate are addressed. The role of sodium-phosphate cotransporter (Slc34a2b) and rhesus (Rh) glycoproteins (ammonia channels) in conjunction with apical V-type H+ ATPase and NHE3 exchangers in these processes are also explored. Nephrocalcinosis is an inflammation-like disorder due to the precipitation of calcareous material in the kidneys, and is listed as one of the most prevalent pathologies in land-based production of salmonids in recirculating aquaculture systems. The causative links underlying the pathogenesis and etiology of nephrocalcinosis in teleosts is speculative at best, but acid-base perturbation is probably a central pathophysiological cause. Relevant risk factors associated with nephrocalcinosis are hypercapnia and hyperoxia in the culture water. These raise internal CO2 levels in the fish, triggering complex branchial and renal acid-base compensations which may promote formation of kidney stones. However, increased salt loads through the rearing water and the feed may increase the prevalence of nephrocalcinosis. An increased understanding of the kidneys role in acid-base and ion regulation and how this relates to renal diseases such as nephrocalcinosis will have applied relevance for the biologist and aquaculturist alike.publishedVersio

New wine in old bottles: Modification of the Na+/K+-ATPase enzyme activity assay and its application in salmonid aquaculture

The Na+, K+ ATPase (NKA) enzyme is important to generate the transmembrane ion gradient in the gills, intestine, and kidneys, hence, is vital for secondary transport of fluids and different solutes in teleosts. Gill NKA enzyme activity is often used as a proxy for parr–smolt transformation (PST) during which anadromous salmonids prepare for seawater (SW). Increased intensification and production of larger smolts in modern salmonid aquaculture has resulted in reports of gill NKA activity being less reliable as a proxy for smolt quality. Consequently, changes in mRNA nka-α1b/α1a ratios in gills are increasingly used as indicators of PST. However, nka isoform mRNA abundance may not reflect translation into the functional protein, nor the activity of the mature enzyme. This may limit the predictive power of molecular markers under certain environmental conditions, rearing regimes and biological scenarios. During PST, the osmoregulatory transformations necessary for SW tolerance and survival does not only occur in the gills. Equally important are the changes in ion transporting activities, including NKA activity, in the intestine and kidneys. However, to our knowledge, there are no previous studies addressing the timing and concurrent changes in NKA activity in the three osmoregulatory tissue during PST. Here we present modifications and optimization of the NKA enzyme activity protocols for gill, intestinal and kidney tissue and outline how to best utilize NKA activity measurements as part of a more holistic approach to evaluate overall smolt quality in modern aquaculture.New wine in old bottles: Modification of the Na+/K+-ATPase enzyme activity assay and its application in salmonid aquaculturepublishedVersio

Betydning av tidspunkt og lengde av vintersignal i RAS for prestasjon i sjø ved utsett av stor smolt

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Betydning av tidspunkt og lengde av vintersignal i RAS for prestasjon i sjø ved utsett av stor smolt

Source at https://nofima.no/.Under kontrollerte forhold i kar var det en positiv effekt av et vintersignal kombinert med brakkvann i RAS på vekst etter overføring til sjøvann. Men et vintersignal ga også økt kjønnsmodning i hannfisk når fisken gikk lenge i RAS på kontinuerlig lys etter at vintersignalet var avsluttet. Kjønnsmodning ble redusert når fisken ble satt ut på lav sjøtemperatur. Resultatene fra utsett i sjømerder viste betydelig høyere dødelighet som følge av vintersår og lavere vekst i sjøfase hos stor smolt på henholdsvis 320 og 850 g satt ut i oktober og januar sammenlignet med fisk satt ut i september ved 160 g. Resultatene fra kar med sjøvann viste ikke store forskjeller i TGC mellom de ulike utsettene, og fisk overført på 320 g hadde høyest TGC i kar. Dødelighet i kar med sjøvann var lav, henholdsvis 0, 0,2 og 1,1 % for de tre utsettene. Forsøket i kar med sjøvann viste at den større smolten har et potensial for god vekst i sjøvann, men også høyere risiko for kjønnsmodning, særlig på høy temperatur i sjøfase. Årsaken til at den større smolten var mer sensitiv mot vintersår og hadde høyere dødelighet i merder i sjø enn mindre fisk som hadde gått lenger i sjø før utbruddet startet bør undersøkes nærmere

Ion transporters and osmoregulation in the kidney of teleost fishes as a function of salinity

Euryhaline teleosts exhibit major changes in renal function as they move between freshwater (FW) and seawater (SW) environments, thus tolerating large fluctuations in salinity. In FW, the kidney excretes large volumes of water through high glomerular filtration rates (GFR) and low tubular reabsorption rates, while actively reabsorbing most ions at high rates. The excreted product has a high urine flow rate (UFR) with a dilute composition. In SW, GFR is greatly reduced, and the tubules reabsorb as much water as possible, while actively secreting divalent ions. The excreted product has a low UFR, and is almost isosmotic to the blood plasma, with Mg2+, SO42–, and Cl– as the major ionic components. Early studies at the organismal level have described these basic patterns, while in the last two decades, studies of regulation at the cell and molecular level have been implemented, though only in a few euryhaline groups (salmonids, eels, tilapias, and fugus). There have been few studies combining the two approaches. The aim of the review is to integrate known aspects of renal physiology (reabsorption and secretion) with more recent advances in molecular water and solute physiology (gene and protein function of transporters). The renal transporters addressed include the subunits of the Na+, K+- ATPase (NKA) enzyme, monovalent ion transporters for Na+, Cl–, and K+ (NKCC1, NKCC2, CLC-K, NCC, ROMK2), water transport pathways [aquaporins (AQP), claudins (CLDN)], and divalent ion transporters for SO42–, Mg2+, and Ca2+ (SLC26A6, SLC26A1, SLC13A1, SLC41A1, CNNM2, CNNM3, NCX1, NCX2, PMCA). For each transport category, we address the current understanding at the molecular level, try to synthesize it with classical knowledge of overall renal function, and highlight knowledge gaps. Future research on the kidney of euryhaline fishes should focus on integrating changes in kidney reabsorption and secretion of ions with changes in transporter function at the cellular and molecular level (gene and protein verification) in different regions of the nephrons. An increased focus on the kidney individually and its functional integration with the other osmoregulatory organs (gills, skin and intestine) in maintaining overall homeostasis will have applied relevance for aquaculture

Sulfate homeostasis in Atlantic salmon is associated with differential regulation of salmonid-specific paralogs in gill and kidney

Sulfate (SO2−4) regulation is challenging for euryhaline species as they deal with large fluctuations of SO2−4 during migratory transitions between freshwater (FW) and seawater (SW), while maintaining a stable plasma SO2−4 concentration. Here, we investigated the regulation and potential role of sulfate transporters in Atlantic salmon during the preparative switch from SO2−4 uptake to secretion. A preparatory increase in kidney and gill sodium/potassium ATPase (Nka) enzyme activity during smolt development indicate preparative osmoregulatory changes. In contrast to gill Nka activity a transient decrease in kidney Nka after direct SW exposure was observed and may be a result of reduced glomerular filtration rates and tubular flow through the kidney. In silico analyses revealed that Atlantic salmon genome comprises a single slc13a1 gene and additional salmonid-specific duplications of slc26a1 and slc26a6a, leading to new paralogs, namely the slc26a1a and -b, and slc26a6a1 and -a2. A kidney-specific increase in slc26a6a1 and slc26a1a during smoltification and SW transfer, suggests an important role of these sulfate transporters in the regulatory shift from absorption to secretion in the kidney. Plasma SO2−4 in FW smolts was 0.70 mM, followed by a transient increase to 1.14 ± 0.33 mM 2 days post-SW transfer, further decreasing to 0.69 ± 0.041 mM after 1 month in SW. Our findings support the vital role of the kidney in SO2−4 excretion through the upregulated slc26a6a1, the most likely secretory transport candidate in fish, which together with the slc26a1a transporter likely removes excess SO2−4 , and ultimately enable the regulation of normal plasma SO2−4 levels in SW

Sulfate homeostasis in Atlantic salmon is associated with differential regulation of salmonid-specific paralogs in gill and kidney

Sulfate (SO2−4) regulation is challenging for euryhaline species as they deal with large fluctuations of SO2−4 during migratory transitions between freshwater (FW) and seawater (SW), while maintaining a stable plasma SO2−4 concentration. Here, we investigated the regulation and potential role of sulfate transporters in Atlantic salmon during the preparative switch from SO2−4 uptake to secretion. A prepara-tory increase in kidney and gill sodium/potassium ATPase (Nka) enzyme activity during smolt development indicate preparative osmoregulatory changes. In con-trast to gill Nka activity a transient decrease in kidney Nka after direct SW expo-sure was observed and may be a result of reduced glomerular filtration rates and tubular flow through the kidney. In silico analyses revealed that Atlantic salmon genome comprises a single slc13a1gene and additional salmonid- specific duplica-tions of slc26a1 and slc26a6a, leading to new paralogs, namely the slc26a1a and - b, and slc26a6a1 and - a2. A kidney- specific increase in slc26a6a1 and slc26a1a during smoltification and SW transfer, suggests an important role of these sul-fate transporters in the regulatory shift from absorption to secretion in the kid-ney. Plasma SO2−4 in FW smolts was 0.70mM, followed by a transient increase to 1.14±0.33mM 2days post- SW transfer, further decreasing to 0.69±0.041mM after 1month in SW. Our findings support the vital role of the kidney in SO2−4 ex-cretion through the upregulated slc26a6a1, the most likely secretory transport can-didate in fish, which together with the slc26a1a transporter likely removes excess SO2−4, and ultimately enable the regulation of normal plasma SO2−4 levels in SW

PigghåFRI – Hvordan unngå problemer med pigghå?

This study has mapped the impact of interaction of spiny dogfish (Squalus acanthias) with aquaculture installations in Norway and studied the behavior of spiny dogfish, in laboratory and field studies, in response to sensory cues for possible development of an anti-shark measure for fish farms. Electromagnetic pulse and smell of dead conspecific (skin extract) induce aversive response without inducing chronic stress in spiny dogfish; orca sound has no effect as repellent against spiny dogfish behaviour. This suggests a promising approach in development of technology based on electromagnetic pulse stimulation and aversive chemical cues to keep spiny dogfish away from fish farms.PigghåFRI – Hvordan unngå problemer med pigghå?publishedVersio