Cell division and DNA replication, in particular in malignant cells, are associated with high glycolysis. An exception to this rule is illustrated by the fact that polyoma transformed hamster cells (BHKpy and NILpy) grow better on galactose than on glucose, yet form only moderate amounts of lactic acid. Moreover, in the total absence of glycolysis (by prolonged exposure to sugar-free modified MEM) several cell functions, such as active transport, kinases, and certain dehydrogenases are regulated upwards (enhancement responses). The sugar starvation phenomenon in non-transformed cells (NIL) manifests itself in density inhibited cultures as well as in dense transformed cultures (NILpy). It has certain features in common with cell physiological modification seen after tumor transformation, such as enhancement of transport, facilitated exchange and enhancement of kinases. However, several criteria readily differentiate the two types of regulation. Although thymidine uptake (into TCA soluble fraction) and active transport of cycloleucine seem to be enhanced in sugar-starved NILpy cultures, the rate of the thymidine incorporation into DNA was found to be greatly lowered in the sugar-starved cultures (approx. 10-20 percent of that of galactose fed cultures). Protein syntheis and turnover will now be examined as will the effect of inhibitors of protein synthesis on the sugar-starvation induced enhancement of cycloleucine transport. The effect of pH on various uptake and transport systems will be examined in a systematic way. Regulations of biosynthesis of specific membrane proteins as a function of tumor virus transformation or of changes in sugar nutrients will be examined by 2-dimensional polyacrylamide gel electrophoresis.