On the comparative turnover rates of the lactate dehydrogenase isozymes in rat tissues

1. 1. An affinity chromatography technique for the determination of turnover parameters has been utilized for the derivation of new data for lactate dehydrogenase and its isozymes in a wide variety of tissues from female rats. 2. 2. This methodology allowed the establishment of relative turnover characteristics in all tissues examined, and the evaluation of rate constants for synthesis and degradation and half-life values in the majority of these enzyme sources. 3. 3. Considerable variation was evident in the turnover characteristics of total protein and lactate dehydrogenase in the different tissues, with the synthesis of the enzyme being highest in reproductive tissues, heart and liver, and degradation most prominent in reproductive tissues. 4. 4. With regard to the isozymes, marked differences in half-lives were evident not only between the same isozyme in different tissues, but also between the various isozymes in any one tissue. 5. 5. Bi-directional trends in the half-life values for the isozyme sequences in several tissues, indicated a distinctive contribution to turnover from the different cell types present. 6. 6. These data have been discussed in relation to the available comparisons in the literature, and the known physiological correlations of lactate dehydrogenase in these tissues