CELL TRANSFORMATION AND DEDIFFERENTIATION .3. CHANGES IN LEUCINE AMINOTRANSFERASE ISOZYMES BY VIRAL TRANSFORMATION AND ITS CORRELATION WITH ISOENZYME CHANGES OCCURRING DURING DIFFERENTIATION

Abstract

The isozyme pattern of leucine aminotransferase (EC 2.6.1.6) in various cell lines and their viral-transformed derivatives were examined. The Wistar 3C rat liver cell line contained only isozyme 1, while its SV 40-transformed counterpart had isozyme III in addition to isozyme I. A spontaneously transformed late passage clone of these liver cells also acquired isozyme III. Polyoma virus-transformed baby hamster kidney cells also contained a greater predominance of isozyme III than their normal untransformed counterpart. Examination of the isozymes in a cloned normal rat kidney cell line transformed by a mutant of Rous sarcoma virus which is temperature-sensitive for transformation indicated that such an isozyme change does correlate with transformation. When grown at 36.degree. C these cells contained predominantly isozyme III; upon reacquiring normal morphology and lowered glucose transport activity when grown at 40.degree. C, their isozyme pattern was changed and consisted predominantly of isozyme I, as is found in normal adult rat kidney tissue. Isozyme III was present in neonatal kidney tissue of the rat and hamster and its predominance in the virus-transformed normal rat and baby hamster kidney cells was interpreted as indicative of the dedifferentiation of these cells upon viral transformation. A similar change of the isozyme pattern of leucine aminotransferase in chicken embryos during their development was observed, such that in 5 day old embryos Form III was predominant while in the more mature differentiated chicken embryo of day 17, Form I was predominant.