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    • Keywords


      Ammoniotelism; ammonium chloride; hyper-ammonia stress; urea cycle; ureogenesis

    • Abstract


      In the present study, the possible role of ureogenesis to avoid the accumulation of toxic ammonia to a lethal level under hyper-ammonia stress was tested in the air-breathing walking catfishClarias batrachus by exposing the fish at 25 mM NH4Cl for 7 days. Excretion of ammonia by the NH4Cl-exposed fish was totally suppressed, which was accompanied by significant accumulation of ammonia in different body tissues. The walking catfish, which is otherwise predominantly ammoniotelic, turned totally towards ureotelism from ammoniotelism with a 5-to 6-fold increase of urea-N excretion during exposure to higher ambient ammonia. Stimulation of ureogenesis was accompanied with significant increase of some of the key urea cycle enzymes such as carbamyl phosphate synthetase (urea cycle-related), argininosuccinate synthetase and argininosuccinate lyase both in hepatic and non-hepatic tissues. Due to this unique physiological strategy of turning towards ureotelism from ammoniotelism via the induced urea cycle, this air-breathing catfish is able to survive in very high ambient ammonia, which they face in certain seasons of the year in the natural habitat.

    • Author Affiliations


      Nirmalendu Saha1 Shritapa Datta1 Kuheli Biswas1 Zaiba Y Kharbuli1

      1. Biochemical Adaptation Laboratory, Department of Zoology, North-Eastern Hill University, Shillong - 793 022, India
    • Dates

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