The initial kinetics of NH3 /NH4+ efflux from L3 Teladorsagia circumcincta

• Published in: Parasitology international 2012-09, Vol.61 (3), p.487-492
• Main Authors: Muhamad, Noorzaid, Walker, Lisa R, Pedley, Kevin C, Simcock, David C, Brown, Simon
• Format: Article
• Language: English
• Subjects: Ammonia - pharmacokinetics; Animals; Energy Metabolism; Gastroenterology and Hepatology; Hydrogen-Ion Concentration; Infectious Disease; Kinetics; Larva - enzymology; Ostertagia - metabolism; Permeability; Phosphates - metabolism; Quaternary Ammonium Compounds - metabolism; Temperature
• ISSN: 1383-5769; 1873-0329
• DOI: 10.1016/j.parint.2012.04.003

Abstract The initial rate of NH3 /NH4+ accumulation in a medium containing L3 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 NH3 /NH4+ did not exceed about 130 μM. The rate of NH3 /NH4+ accumulation increased with temperature between 4 °C and 37 °C, declined with increasing pH or increasing external NH3 /NH4+ 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 NH3 /NH4+ is a diffusive process and that the secreted or excreted NH3 /NH4+ is generated enzymatically rather than dissociating from the surface of the nematode. The enzymatic source of the NH3 /NH4+ is yet to be identified. Since the concentration of NH3 /NH4+ in the rumen and abomasum is higher than 130 μM, it is unlikely that T. circumcincta contributes to it, but NH3 /NH4+ may be accumulated from the rumen fluid by the nematode.