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Hyper-ammonia stress causes induction of inducible nitric oxide synthase gene and more production of nitric oxide in air-breathing magur catfish, Clarias magur (Hamilton)

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Abstract

Nitric oxide (NO) is an important signalling molecule that plays diverse physiological functions in several vertebrates including that of adaptation to various stressful stimuli. The air-breathing magur catfish (Clarias magur) is known to tolerate a very high external ammonia (HEA) stress in its natural habitats. We report here the possible induction of inducible nitric oxide (inos) gene and more generation of NO in magur catfish exposed to HEA. Exposure to HEA (25 mM NH4Cl) for 14 days led to the higher accumulation of NO in different tissues of magur catfish and also more efflux of NO from the perfused liver of NH4Cl-treated fish as a consequence of high build of toxic ammonia in body tissues. More synthesis and accumulation of NO in body tissues was associated with the induction of iNOS activity, which otherwise was not detectable in control fish. The stimulation of iNOS activity in HEA exposed fish was mainly due to induction of inos gene as evidenced by more expression of inos mRNA and also more abundance of iNOS protein in different tissues of magur catfish. Immunocytochemical analysis indicated the zonal specific expression of iNOS protein in different tissues of magur catfish. The augmentation of iNOS in the fish under HEA could be an adaptive strategy of the fish to defend against the ammonia stress through the generation of NO. Therefore, the present finding identifies the potential role of iNOS to enhance the adaptive capacity and survivability of catfish under various adverse environmental and pathological conditions that it faces in its natural habitats.

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Acknowledgements

This study was supported by projects sanctioned to N. S. by the Science and Engineering Research Board, Department of Science and Technology, New Delhi, National Agricultural Science Fund, Indian Council of Agricultural Research, New Delhi, and the University Grants Commission, New Delhi. Rajiv Gandhi National Fellowship received by S.K is gratefully acknowledged.

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Correspondence to Nirmalendu Saha.

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All animal experimentations were approved by the Animal Ethics Committee of North-Eastern Hill University, Shillong (No. IEC/NEHU/Ph.D./NOC/47). Furthermore, all experimental methods were performed according to the relevant guidelines and regulations of Animal Ethics Committee.

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Kumari, S., Choudhury, M.G. & Saha, N. Hyper-ammonia stress causes induction of inducible nitric oxide synthase gene and more production of nitric oxide in air-breathing magur catfish, Clarias magur (Hamilton). Fish Physiol Biochem 45, 907–920 (2019). https://doi.org/10.1007/s10695-018-0593-y

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  • DOI: https://doi.org/10.1007/s10695-018-0593-y

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