Changes in the activity of lactate dehydrogenase isoformes in mouse rhabdomyosarcoma under different proliferation conditions

: The activity of lactate dehydrogenase (LDH) isoenzymes was studied in clones of rhabdomyosarcoma (RMS) MX-53, being transplanted on mice of CC57W line. Clones obtained in lungs after the intravenous injection of a tumor cell suspension were transplanted into subcutaneous connective tissue (SCT) and eye anterior chamber (EAC). A study of LDH isoenzymes spectrum in transplants and native muscle tissues has been made using polyacrylamide gel electrophoresis and densitometry. We revealed a variability of LDH isoenzyme activity within one clone, and in population of clones under different proliferation conditions. Under all the proliferation conditions, we observed spectra characteristic of tumors of a given histogenesis with predominating activity of M-subunits. But during proliferation in EAC the M:H ratio decreased, and LDH spectra of tumor cells became more similar to the LDH spectrum of normal skeletal muscles. It is concluded that intra- and interclonal variations of the character "LDH isozyme spectrum" is strongly influenced by the environmental factors.