Abnormal mobility of serum lactate dehydrogenase isoenzymes during electrophoresis.

An unusual electrophoretic pattern for the isoenzymes of serum lactate dehy­ drogenase (LD; EC 1.1.1.27) was ob­ served. Two diffuse bands of LD activity w ere seen in the reg ion of the electropherogram in which LD-4 and LD-5 normally migrate, when this serum was fractionated by cellulose acetate e lec­ trophoresis (figure 1-A). One of the bands appeared to have the same mobility as LD -4 w ith the second band m ore cathodic, but less so than normal LD-5. Those bands normally seen as the most anodic, LD-1, LD-2 and LD-3, were not visible. A mixture of equal volumes of the serum w ith the unusual pattern and another serum with LD isoenzym es of normal mobility (although apparently elevated LD-5; figure 1-C) yielded an LD pattern which was of abnormal mobility (figure 1-B). Further study revealed that even when the mixture consisted of 10 percent by volume of the unusual serum, a signifi­ cant alteration of the normal mobility was 489 observed. The ability of the serum to pro­ duce this effect was not elim inated by prior heat-treatm ent (53°C, 60 min). The procedure for electrophoresis was essentially that provided in the Helena Laboratories Instruction Manual.* T o ta l serum LD ac tiv ity was only slightly elevated or normal in specimens y ie ld in g th is p a tte rn . T he im m unoelectrophoretic pattern did not appear dif­ ferent from a normal control w hen deter­ m ined with polyvalent, IgA, IgG, IgM, kappa and lambda antisera by conven­ tional means. Levels of IgG, IgM and IgA, determ ined by radial immunodiffusion, were w ithin the normal range. T he serum was from a 51-year old fem ale who, w hen exam ined in 1971, p re s e n te d w ith h y p e rte n s io n , over­ weight, slightly enlarged heart and some ao rtic sc le ro sis . H er serum LD was slightly elevated, bu t fractionation was w ithin normal limits. At the time the specim en with the un­ usual pattern was drawn (approximately