Please use this identifier to cite or link to this item: https://doi.org/10.1007/s00360-004-0444-2
Title: The ammonotelic African lungfish, Protopterus dolloi, increases the rate of urea synthesis and becomes ureotelic after feeding
Authors: Lim, C.K.
Wong, W.P.
Lee, S.M.L.
Chew, S.F.
Ip, Y.K. 
Keywords: Feeding
Lungfish
Nitrogen metabolism
Protopterus dolloi
Urea
Issue Date: Oct-2004
Citation: Lim, C.K., Wong, W.P., Lee, S.M.L., Chew, S.F., Ip, Y.K. (2004-10). The ammonotelic African lungfish, Protopterus dolloi, increases the rate of urea synthesis and becomes ureotelic after feeding. Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology 174 (7) : 555-564. ScholarBank@NUS Repository. https://doi.org/10.1007/s00360-004-0444-2
Abstract: This study aimed to elucidate the role of urea synthesis in the slender African lungfish Protopterus dolloi in detoxifying ammonia after feeding. There were significant increases in the rate of ammonia excretion in P. dolloi between hours 6 and 15 after feeding. Simultaneously, there were significant increases in urea excretion rates between hours 3 and 18. Consequently, the percentage of total nitrogen (N) excreted as urea N increased to ∼60% between hours 12 and 21 post-feeding. Hence, after feeding, the normally ammonotelic P. dolloi became ureotelic. Approximately 41% of the N intake from food was excreted within 24 h by P. dolloi, 55% of which was in the form of urea N. At hour 12 post-feeding, the accumulation of urea N was greater than the accumulation of ammonia N in various tissues, which indicates that feeding led to an increase in the rate of urea synthesis. This is contrary to results reported previously on the infusion of ammonia into the peritoneal cavity of the marine dogfish shark, in which a significant portion of the exogenous ammonia was excreted as ammonia. In contrast, feeding is more likely to induce urea synthesis, which is energy intensive, because feeding provides an ample supply of energy resources and leads to the production of ammonia intracellularly in the liver. The capacity of P. dolloi to synthesize urea effectively prevented a postprandial surge in the plasma ammonia level as reported elsewhere for other non-ureogenic teleosts. However, there was a significant increase in the glutamine content in the brain at hour 24, indicating that the brain had to defend against ammonia toxicity after feeding. © Springer-Verlag 2004.
Source Title: Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology
URI: http://scholarbank.nus.edu.sg/handle/10635/101858
ISSN: 01741578
DOI: 10.1007/s00360-004-0444-2
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