title: L-leucine transport in liver of Antarctic fish in vivo at 0 degrees C.
abstract: Uptake of L-[14C]leucine by liver of an endemic Antarctic fish, Trematomus hansoni, was studied by a single injection technique with [3H]inulin as a reference. Rate constants for leucine influx and efflux and incorporation into liver protein were determined by analysis of isotope distribution in the free and protein-bound compartments of liver and in blood draining the liver at various times after injection. Transport rates were slower than in temperate fish at 20 degrees C, but saturation properties and ability to accumulate leucine in liver were comparable. Kinetic analysis indicated that 30% of uptake at 0 degrees C was due to active transport, similar to that in toadfish at 20 degrees C. This contrasts with the absence of this component in toadfish cooled to 10 degrees C. Average polypeptide chain assembly time was 19 min at 0 degrees C. Transport functions were maintained in fish warmed to 10 degrees C; however, protein synthesis declined at temperatures above 5 degrees C. The results indicate this system is adapted to function at extremely low temperatures in a manner qualitatively similar to organisms adapted to much higher temperatures. Transport and synthetic rates, however, were low, consistent with a normal temperature dependency (Q10 about 2.5) for biological reaction rates.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D002250:Carbon Radioisotopes; D003080:Cold Temperature; D005260:Female; D005399:Fishes / Q000378:metabolism*; D007930:Leucine / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008297:Male; D008433:Mathematics
chemical_list: D002250:Carbon Radioisotopes; D007930:Leucine