scholarly journals Revisiting the effects of crowding and feeding in the gulf toadfish, Opsanus beta: the role of Rhesus glycoproteins in nitrogen metabolism and excretion

2011 ◽  
Vol 215 (2) ◽  
pp. 301-313 ◽  
Author(s):  
T. M. Rodela ◽  
A. J. Esbaugh ◽  
D. Weihrauch ◽  
C. M. Veauvy ◽  
M. D. McDonald ◽  
...  
Keyword(s):  
Nitrogen Metabolism ◽  
Opsanus Beta ◽  
Gulf Toadfish

Ammonia affects brain nitrogen metabolism but not hydration status in the Gulf toadfish (Opsanus beta)

2005 ◽  
Vol 74 (1) ◽  
pp. 32-46 ◽  
Author(s):  
Clémence M. Veauvy ◽  
M. Danielle McDonald ◽  
Johan Van Audekerke ◽  
Greet Vanhoutte ◽  
Nadja Van Camp ◽  
...  
Keyword(s):  
Nitrogen Metabolism ◽  
Hydration Status ◽  
Opsanus Beta ◽  
Gulf Toadfish

Guanylin peptides regulate electrolyte and fluid transport in the Gulf toadfish (Opsanus beta) posterior intestine

2014 ◽  
Vol 307 (9) ◽  
pp. R1167-R1179 ◽  
Author(s):  
Ilan M. Ruhr ◽  
Charlotte Bodinier ◽  
Edward M. Mager ◽  
Andrew J. Esbaugh ◽  
Cameron Williams ◽  
...  
Keyword(s):  
Fluid Transport ◽  
Short Circuit ◽  
Secretory Response ◽  
Seawater Adaptation ◽  
Posterior Intestine ◽  
Ussing Chambers ◽  
Opsanus Beta ◽  
Anterior Intestine ◽  
Gulf Toadfish

The physiological effects of guanylin (GN) and uroguanylin (UGN) on fluid and electrolyte transport in the teleost fish intestine have yet to be thoroughly investigated. In the present study, the effects of GN, UGN, and renoguanylin (RGN; a GN and UGN homolog) on short-circuit current ( Isc) and the transport of Cl−, Na+, bicarbonate (HCO3−), and fluid in the Gulf toadfish ( Opsanus beta) intestine were determined using Ussing chambers, pH-stat titration, and intestinal sac experiments. GN, UGN, and RGN reversed the Isc of the posterior intestine (absorptive-to-secretory), but not of the anterior intestine. RGN decreased baseline HCO3− secretion, but increased Cl− and fluid secretion in the posterior intestine. The secretory response of the posterior intestine coincides with the presence of basolateral NKCC1 and apical cystic fibrosis transmembrane conductance regulator (CFTR), the latter of which is lacking in the anterior intestine and is not permeable to HCO3− in the posterior intestine. However, the response to RGN by the posterior intestine is counterintuitive given the known role of the marine teleost intestine as a salt- and water-absorbing organ. These data demonstrate that marine teleosts possess a tissue-specific secretory response, apparently associated with seawater adaptation, the exact role of which remains to be determined.

scholarly journals The role of the rectum in osmoregulation and the potential effect of renoguanylin on SLC26a6 transport activity in the Gulf toadfish (Opsanus beta)

2016 ◽  
Vol 311 (1) ◽  
pp. R179-R191 ◽  
Author(s):  
Ilan M. Ruhr ◽  
Yoshio Takei ◽  
Martin Grosell
Keyword(s):  
Water Absorption ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Potential Effect ◽  
Posterior Intestine ◽  
Distal Intestine ◽  
Opsanus Beta ◽  
Ion Absorption ◽  
Gulf Toadfish

Teleosts living in seawater continually absorb water across the intestine to compensate for branchial water loss to the environment. The present study reveals that the Gulf toadfish ( Opsanus beta) rectum plays a comparable role to the posterior intestine in ion and water absorption. However, the posterior intestine appears to rely more on SLC26a6 (a HCO3−/Cl− antiporter) and the rectum appears to rely on NKCC2 (SLC12a1) for the purposes of solute-coupled water absorption. The present study also demonstrates that the rectum responds to renoguanylin (RGN), a member of the guanylin family of peptides that alters the normal osmoregulatory processes of the distal intestine, by inhibited water absorption. RGN decreases rectal water absorption more greatly than in the posterior intestine and leads to net Na+ and Cl− secretion, and a reversal of the absorptive short-circuit current ( ISC). It is hypothesized that maintaining a larger fluid volume within the distal segments of intestinal tract facilitates the removal of CaCO3 precipitates and other solids from the intestine. Indeed, the expression of the components of the Cl−-secretory response, apical CFTR, and basolateral NKCC1 (SLC12a2), are upregulated in the rectum of the Gulf toadfish after 96 h in 60 ppt, an exposure that increases CaCO3 precipitate formation relative to 35 ppt. Moreover, the downstream intracellular effects of RGN appear to directly inhibit ion absorption by NKCC2 and anion exchange by SLC26a6. Overall, the present findings elucidate key electrophysiological differences between the posterior intestine and rectum of Gulf toadfish and the potent regulatory role renoguanylin plays in osmoregulation.

EFFECTS OF AMMONIA ON SURVIVAL, SWIMMING AND ACTIVITIES OF ENZYMES OF NITROGEN METABOLISM IN THE LAKE MAGADI TILAPIA OREOCHROMIS ALCALICUS GRAHAMI

1993 ◽  
Vol 180 (1) ◽  
pp. 323-327 ◽  
Author(s):  
P. J. Walsh ◽  
H. L. Bergman ◽  
A. Narahara ◽  
C. M. Wood ◽  
P. A. Wright ◽  
...  
Keyword(s):  
Nitrogen Metabolism ◽  
Swimming Performance ◽  
Ammonia Excretion ◽  
Ammonia Toxicity ◽  
Short Term ◽  
Opsanus Beta ◽  
Lake Magadi ◽  
High Ammonia ◽  
Unionized Ammonia ◽  
Ammonia Exposure

The Lake Magadi tilapia, Oreochromis alcalicus grahami, is remarkable among teleosts in that it flourishes under extremely well-buffered alkaline water conditions (pH 10, CCO2 180 mmol l-1) at temperatures of 30–40 °C (Wood et al. 1989). As expected from current models in teleosts, ammonia excretion into such water would be difficult at best (Wood, 1993). Part of the survival strategy of the Lake Magadi tilapia is that it has a complete ornithine-urea cycle (O-UC) in the liver and excretes virtually all of its waste nitrogen as urea (Randall et al. 1989). Ammonia toxicity in ammoniotelic teleosts has been studied extensively, and typical values for unionized ammonia (NH3) 96 h LC50 (the concentration at which half of test subjects die after 96 h) are well below 100 micromolar (Haywood, 1983; Thurston et al. 1983a,b; Campbell, 1991). Surprisingly, no ammonia LC50 values are available for ureogenic teleost fish, and one would predict that fish synthesizing and excreting urea for whatever purpose would have higher LC50 values than their ammoniotelic counterparts. Additionally, since ammonia exposure has been implicated in the functional response of urea excretion in the Lake Magadi tilapia (Wood et al. 1989) and another ureogenic teleost (the gulf toadfish Opsanus beta) (Walsh et al. 1990), we reasoned that ammonia exposure in the Lake Magadi tilapia might reveal insights into the biochemical regulation of the O-UC in this species; in particular that it might induce enzyme activity. We report here that the Lake Magadi tilapia has a rather high ammonia LC50 compared to values for other teleosts, but that short-term ammonia exposure has very limited effects on the activities of the enzymes of nitrogen metabolism and on swimming performance.

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