LACTATE-DEHYDROGENASE ISOENZYMES IN SERUM OF MAMMALIAN AND AVIAN ORIGIN

In the article we describe characteristics of lactate dehydrogenase (LD) (EC 1.1.1.27) isoenzymes of fowl origin. We compare them with characteristics of evolutionary different mammalian forms of the enzyme. Separations of LD isoenzymes have been done using the most progressive electrophoretic techniques available at present. They included electrophoresis in homogeneous and gradient polyacrylamide gels (PAGE) as well as isoelectric focusing (IEF). A typical densitometric pattern of serum LD isoenzymes obtained by gradient PAGE is illustrated in Fig. 1. It is obvious that LD isoenzymes of all investigated animals have been well separated under applied experimental conditions, with an exception of fowl serum. We succeeded in separating fowl LD isoenzymes using isoelectric focusing. It was possible to distinguish five fractions of lactate dehydrogenase (Fig. 2) by this technique.As shown in Fig. 2, mobility of avian isoenzymes in the gradient of pH differs from that of their mammalian analogues. Fowl LD isoenzymes were localized in cathodic part of IEF-gram. In the case of mammalian isoenzymes (cattle and rabbit), we found LD4 and LD5 forms of the enzyme in this part. The major fractions, i. e. LD1 to LD3 were present in anodic part of IEF-gram. We quantitatively expressed this different mobility of mammalian and avian forms of LD using retention factors R(f) (Tab. III). A migration distance of cattle LD1 served as a reference point. It could be seen from a comparison of R(f) values that avian forms of LD (of galiform origin) differed from mammalian ones by an outstanding shift of their isoelectric points, especially that of LD1, toward basic values. The total LD activity (IU) and the relative distribution of the LD isoenzyme activities (%) in normal serum of various animals are listed in Tabs I and II. A comparison of these values showed that, in contrast to mammalian serum (with the exception of the rat one), LDs was the predominant fraction in fowl serum, followed by LD4. LD1 to LD3 occurred in low amounts with fairly similar proportions. On the other hand, most of mammalian serum revealed a reverse pattern of LD isoenzymes, i. e. predominant portion of serum activity had been concentrated in the first three anodic fractions and LD4 and LD5 had been found to be minor ones.