Ammonia movement and distribution after exercise across white muscle cell membranes in rainbow trout

摘要: Manipulations of pH and electrical gradients in a perfused preparation were used to analyze the factors controlling ammonia distribution flux trout white muscle after exercise. Trout exercised exhaustion, then an isolated-perfused with discrete arterial inflow venous outflow was made from posterior portion tail. The tail-trunks low (7.4)-, medium (7.9)-, high (8.4)-pH saline, achieved by varying HCO3- concentration ([HCO3-]) at constant Pco2. Intracellular extracellular pH, ammonia, CO2, K+, Na+, Cl- measured. Muscle intracellular not affected changes pH. Increasing caused decrease transmembrane NH3 partial pressure (PNH3) gradient efflux. When K+ increased 3.5 15 mM medium-pH group, depolarization cell membrane potential -92 -60 mV 0.1-unit depression occurred. Ammonia efflux despite marked reduction PNH3 gradient. Amiloride (10(-4) M) had no effect, indicating that Na+/H(+)-NH4+ exchange does participate transport this system. A comparison observed intracellular-to-extracellular ratios those modeled according either or Nernst distributions supports model which across membranes is both gradients, are permeable NH4+. Membrane potential, acting retain levels NH4+ compartment, appears have dominant influence during postexercise period. However, rest, may be more important, resulting much lower ratios. We speculate NH3-to-NH4+ permeability ratio change between rest condition.