caa a22 4500 605514410 CHVBK 20210128100704.0 cr unu---uuuuu 210128e20150701xx s 000 0 eng 10.1007/s00360-015-0898-4 doi (NATIONALLICENCE)springer-10.1007/s00360-015-0898-4 Nitrogen metabolism, acid-base regulation, and molecular responses to ammonia and acid infusions in the spiny dogfish shark ( Squalus acanthias ) [Elektronische Daten] [C. Nawata, Patrick Walsh, Chris Wood] Although they are ureotelic, marine elasmobranchs express Rh glycoproteins, putative ammonia channels. To address questions raised by a recent study on high environmental ammonia (HEA) exposure, dogfish were intravascularly infused for 24h at 3mlkg−1 h−1 with isosmotic NaCl (500mmoll−1, control), NH4HCO3 (500mmoll−1), NH4Cl (500mmoll−1), or HCl (as 125mmoll−1 HCl+375mmoll−1 NaCl). While NaCl had no effect on arterial acid-base status, NH4HCO3 caused mild alkalosis, NH4Cl caused strong acidosis, and HCl caused lesser acidosis, all predominantly metabolic in nature. Total plasma ammonia (TAmm) and excretion rates of ammonia (J Amm) and urea-N (J Urea-N) were unaffected by NaCl or HCl. However, despite equal loading rates, plasma TAmm increased to a greater extent with NH4Cl, while J Amm increased to a greater extent with NH4HCO3 due to much greater increases in blood-to-water PNH3 gradients. As with HEA, both treatments caused large (90%) elevations of J Urea-N, indicating that urea-N synthesis by the ornithine-urea cycle (OUC) is driven primarily by ammonia rather than HCO3 −. Branchial mRNA expressions of Rhbg and Rhp2 were unaffected by NH4HCO3 or NH4Cl, but v-type H +-ATPase was down-regulated by both treatments, and Rhbg and Na+/H+ exchanger NHE2 were up-regulated by HCl. In the kidney, Rhbg was unresponsive to all treatments, but Rhp2 was up-regulated by HCl, and the urea transporter UT was up-regulated by HCl and NH4Cl. These responses are discussed in the context of current ideas about branchial, renal, and OUC function in this nitrogen-limited predator. Springer-Verlag Berlin Heidelberg, 2015 Elasmobranchs nationallicence Rh glycoproteins nationallicence Gene expression nationallicence Urea nationallicence Ammonia nationallicence HCl nationallicence NH4Cl nationallicence NH4HCO3 nationallicence Gills nationallicence Kidney nationallicence Rhp2 nationallicence Ornithine-urea cycle nationallicence Nawata C. Bamfield Marine Sciences Centre, 100 Pachena Road, V0R 1B0, Bamfield, BC, Canada aut Walsh Patrick Bamfield Marine Sciences Centre, 100 Pachena Road, V0R 1B0, Bamfield, BC, Canada aut Wood Chris Bamfield Marine Sciences Centre, 100 Pachena Road, V0R 1B0, Bamfield, BC, Canada aut Journal of Comparative Physiology B Springer Berlin Heidelberg 185/5(2015-07-01), 511-525 0174-1578 185:5<511 2015 185 360 https://doi.org/10.1007/s00360-015-0898-4 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00360-015-0898-4 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Nawata C. Bamfield Marine Sciences Centre, 100 Pachena Road, V0R 1B0, Bamfield, BC, Canada aut NATIONALLICENCE 700 1- Walsh Patrick Bamfield Marine Sciences Centre, 100 Pachena Road, V0R 1B0, Bamfield, BC, Canada aut NATIONALLICENCE 700 1- Wood Chris Bamfield Marine Sciences Centre, 100 Pachena Road, V0R 1B0, Bamfield, BC, Canada aut NATIONALLICENCE 773 0- Journal of Comparative Physiology B Springer Berlin Heidelberg 185/5(2015-07-01), 511-525 0174-1578 185:5<511 2015 185 360