Distribution and regulation of deoxythymidine kinase activity in differentiating cells of mammalian intestines.

SUMMARY The distribution of deoxythymidine kinase activity has been reexamined in rat and human intestinal mucosa separated by a planing technique into cells in different stages of differentiation. When epithelial cells leave the crypts, a decrease in kinase activity was observed in both resuspended pellet and supernatant fractions. Commercial preparations of phospholipase C added to the assay system resulted in remarkable stimulation of kinase activity, an effect that was more pronounced in extracts from rat tissues and in pellet fractions of all the tissues studied. Although pellet activity in preparations from human mucosa was primarily associated with the nuclear fraction, significant activity was also found in the mitochondrial fraction. The effects of phospholipase C and/or detergents varied consid erably with the various subcellular fractions. The degree of stimulation by phospholipase C appeared to be inversely related to the level of deoxythymidine kinase activity present under standard assay conditions. The implications of some aspects of these observations have been discussed.