Thermal sensitivity of white muscle lactate dehydrogenase isolated from a lake trout, (Salmo trutta), inhabiting lake Plav, Montenegro

Abstract

To shed light on thermoadaptive properties of Salmo trutta from lake Plav (Montenegro), we undertook kinetic studies of pyruvate reduction rates and thermal stability analyses of white muscle LDH. We compared these with the data obtained for trout of the same, confirmed by us, Danubian lineage living in rivers and streams of Serbia and Montenegro. We also tested the effect of acclimation in captivity at 4 and 14 A degrees C. The lake trout was of a typical smoltified phenotype (the size, the elongated silver colored body). At physiological substrate concentration, the breaks in the Arrhenius plots (critical temperature - T-c) correlated with acclimation temperatures or habitat water temperatures. Q(10) values for temperatures above T-c were close to one, in all cases except 4 A degrees C acclimated trout. At temperatures below T-c Q(10) was close to two, except in the case of 14 A degrees C acclimated trout. Lake trout had a highest Q(10) values at temperatures below T-c. It was conspicuous that within the entire range of tested temperatures the differences in Q(10) resulted from the effect of environmental temperature. Higher Q(10) values were obtained with LDH isolated from trout acclimated to 4 A degrees C compared with LDH acclimated to 14 A degrees C. E-a values were much lower at a temperature below T-c compared with temperatures above Tc. Thermal stability of muscle LDH was lower after acclimation to 14 compared to 4 A degrees C, while extremely high thermostability was obtained with the lake trout enzyme. Our data support the concept that T-c values have distinct physiological significance.