Adlimoghaddam 2015 J Exp Biol

Adlimoghaddam A, Boeckstaens M, Marini AM, Treberg JR, Brassinga AK, Weihrauch D (2015) Ammonia excretion in Caenorhabditis elegans: mechanism and evidence of ammonia transport of the Rhesus protein CeRhr-1. J Exp Biol 218:675-83.

» PMID:25740900 Open Access

Adlimoghaddam A, Boeckstaens M, Marini AM, Treberg JR, Brassinga AK, Weihrauch D (2015) J Exp Biol

Abstract: The soil-dwelling nematode Caenorhabditis elegans is a bacteriovorous animal, excreting the vast majority of its nitrogenous waste as ammonia (25.3±1.2 µmol gFW^-1 day^-1) and very little urea (0.21±0.004 µmol gFW^-1 day^-1). Although these roundworms have been used for decades as genetic model systems, very little is known about their strategy to eliminate the toxic waste product ammonia from their bodies into the environment. The current study provides evidence that ammonia is at least partially excreted via the hypodermis. Starvation reduced the ammonia excretion rates by more than half, whereas mRNA expression levels of the Rhesus protein CeRhr-2, V-type H⁺-ATPase (subunit A) and Na⁺/K⁺-ATPase (α-subunit) decreased correspondingly. Moreover, ammonia excretion rates were enhanced in media buffered to pH 5 and decreased at pH 9.5. Inhibitor experiments, combined with enzyme activity measurements and mRNA expression analyses, further suggested that the excretion mechanism involves the participation of the V-type H⁺-ATPase, carbonic anhydrase, Na⁺/K⁺-ATPase, and a functional microtubule network. These findings indicate that ammonia is excreted, not only by apical ammonia trapping, but also via vesicular transport and exocytosis. Exposure to 1 mmol l^-1 NH4Cl caused a 10-fold increase in body ammonia and a tripling of ammonia excretion rates. Gene expression levels of CeRhr-1 and CeRhr-2, V-ATPase and Na⁺/K⁺-ATPase also increased significantly in response to 1 mmol l^-1 NH4Cl. Importantly, a functional expression analysis showed, for the first time, ammonia transport capabilities for CeRhr-1 in a phylogenetically ancient invertebrate system, identifying these proteins as potential functional precursors to the vertebrate ammonia-transporting Rh-glycoproteins. • Keywords: Vesicular transport, Na⁺/K⁺-ATPase, V-ATPase, Carbonic anhydrase

• O2k-Network Lab: CA Winnipeg Treberg JR

Labels: MiParea: Respiration, Comparative MiP;environmental MiP 

Organism: Caenorhabditis elegans 

Preparation: Intact organism 

Regulation: ATP production  Coupling state: ROUTINE 

HRR: Oxygraph-2k