PAH secretion in the urinary bladder of a crab Cancer borealis.
Uptake of 10 microM p-aminohippuric acid (PAH) by sections of Cancer borealis urinary bladder was concentrative, saturable (Km 67 microM, Vmax 1.7 nmol.mg tissue-1.h-1), inhibitable by other organic anions, and dependent on medium Na and glycolytic metabolism. Bladders mounted in flux chambers exhibited net secretory transport of PAH, with serosa-to-lumen fluxes (Js leads to l) being about 4 times lumen-to-serosa fluxes (Jl leads to s). In 60-min flux chamber studies, tissue-to-medium ratios exceeded unity with serosal, but not luminal, PAH. Initial (10 min) fluxes and tissue accumulations (Ac) were measured in the absence and presence of 1-5 mM BCG (bromocresol green; competitor organic anion). With serosal PAH, serosal BCG (1 mM) reduced serosa-to cell flux (Js leads to c), Ac, and Jc leads to l by 60-75%. With luminal PAH, luminal BCG (1 mM) had no effect on Jl leads to c, Ac, or Jc leads to s; increasing the luminal BCG concentration to 5 mM reduced Jl leads to c, Ac, and Jc leads to s by 40-50%. The data are consistent with a model featuring an inwardly directed pump on the serosal membrane, cellular accumulation, and a facilitated carrier on the luminal membrane.
D000618:Aminohippuric Acids / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D003386:Brachyura; D001961:Bromcresol Green; D007700:Kinetics; D008297:Male; D001743:Urinary Bladder / Q000187:drug effects / Q000502:physiology*; D010130:p-Aminohippuric Acid / Q000378:metabolism*
D000618:Aminohippuric Acids; D001961:Bromcresol Green; D010130:p-Aminohippuric Acid