title: Characteristics of leucine transport by isolated hepatocytes of Antarctic fish at low temperatures.
abstract: Hepatocytes prepared by collagenase perfusion from Antarctic nototheniid fish of genus Trematomus are active in uptake of [14C]leucine at 0, 5, and 10 degrees C. The system is saturable with apparent Km about 1.0 mM. Isoleucine and phenylalanine were major competitors, valine was about one-half as effective, while alanine, glycine and histidine had no effect. Temperature dependency of rates in the 0-10 degrees C range yielded Ea = 65 kJ/mol (Q10 = 2.7). The average first-order rate constant at 0 degrees C was 0.1 min-1, one-third the value of 0.3 min-1 estimated for clearance of [14C]leucine by liver of these species in vivo. Affinity and specificity agreed well with in vivo data on liver clearance of leucine, both in Antarctic fish at 0 degrees C and in temperate fish acclimated to 10 degrees C and 20 degrees C. The results indicate similar modifications of leucine transport associated with evolutionary cold adaptation and seasonal acclimation in fish.
mesh_terms: D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D000864:Antarctic Regions; D001692:Biological Transport / Q000187:drug effects; D003081:Cold Climate; D005399:Fishes / Q000378:metabolism*; D066298:In Vitro Techniques; D007700:Kinetics; D007930:Leucine / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D013696:Temperature
chemical_list: D000596:Amino Acids; D007930:Leucine