title: The initial kinetics of NH3/NH4(+) efflux from L3 Teladorsagia circumcincta.
abstract: The initial rate of NH(3)/NH(4)(+) accumulation in a medium containing L(3) Teladorsagia circumcincta was 0.18-0.6 pmol h(-1) larva(-1), which increased linearly with larval density. However it appeared that the larva-generated external concentration of NH(3)/NH(4)(+) did not exceed about 130 μM. The rate of NH(3)/NH(4)(+) accumulation increased with temperature between 4 °C and 37 °C, declined with increasing pH or increasing external NH(3)/NH(4)(+) concentration and was not significantly affected by the concentration of the phosphate buffer or by exsheathing the larvae. We infer from these data that the efflux of NH(3)/NH(4)(+) is a diffusive process and that the secreted or excreted NH(3)/NH(4)(+) is generated enzymatically rather than dissociating from the surface of the nematode. The enzymatic source of the NH(3)/NH(4)(+) is yet to be identified. Since the concentration of NH(3)/NH(4)(+) in the rumen and abomasum is higher than 130 μM, it is unlikely that T. circumcincta contributes to it, but NH(3)/NH(4)(+) may be accumulated from the rumen fluid by the nematode.
authors.affiliation: Universiti Kuala Lumpur, Royal College of Medicine Perak, 3 Greentown Road, 30450 Ipoh, Perak, Malaysia.
authors.forename: Noorzaid
authors.initials: N
authors.lastname: Muhamad
authors.forename: Lisa R
authors.initials: LR
authors.lastname: Walker
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Pedley
authors.forename: David C
authors.initials: DC
authors.lastname: Simcock
authors.forename: Simon
authors.initials: S
authors.lastname: Brown
mesh_terms: D000641:Ammonia / Q000493:pharmacokinetics*; D000818:Animals; D004734:Energy Metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007814:Larva / Q000201:enzymology; D010028:Ostertagia / Q000378:metabolism*; D010539:Permeability; D010710:Phosphates / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D013696:Temperature
chemical_list: D010710:Phosphates; D000644:Quaternary Ammonium Compounds; D000641:Ammonia