New Insights into Ammonia Transport
Sponsored by the APS Cell & Molecular Physiology Section

The recent identification that specific proteins mediate transmembrane ammonia transport may revolutionize our understanding of the physiologic mechanisms underlying ammonia metabolism.  Previous work had suggested that ammonia transport occurred primarily through non-ionic diffusion of NH₃.  Increasing evidence, obtained from a wide variety of techniques, suggests that a specific family of proteins (Mep/Amt/Rh glycoprotein), mediate specific and regulated NH₃ transport.  Some of the most recent work has been published in Science (Science  305: 1587-1594, 2004), PNAS (Proc Natl Acad Sci U S A  101: 17090-17095, 2004; Proc Natl Acad Sci U S A  101: 7787-7792, 2004), JBC (J Biol Chem  279: 17443-17448, 2004, J Biol Chem  277: 12499-12502, 2002) and in several Am J Physiol journals (Am J Physiol Gastrointest Liver Physiol  DOI, 10.1152/ ajpgi.00418.2004, 2004; Am J Physiol Renal Physiol  287: F628-F638, 2004; Am J Physiol Renal Physiol  284: F323-F337, 2003).  The goal of this symposium is to summarize current knowledge in this rapidly progressing field.  Separate talks would summarize:  1) Identification of the tertiary structure of the bacterial ammonia transporter family, AmtB; 2) Transport characteristics of mammalian ammonia transporter family members; 3) Expression and regulation of mammalian ammonia transporter family members in the kidney, liver, gastrointestinal tract and other organs; 4) Evidence that members of ammonia transporter family may mediate CO₂ transport.  A balanced and multi-disciplinary approach to this rapidly emerging field should result from this symposium.