Creatine accumulation and exchange by HEK293 cells stably expressing high levels of a creatine transporter

We have generated a stable HEK293 cell line expressing high levels of a cre atine transporter (CREAT). This cell line (HEK293-CREAT) was used to study the properties of GREAT in terms of the accumulation and release of creatin e. HEK293-CREAT cells accumulated high steady state levels of creatine unde r saturating creatine levels (approx. 25-fold higher intracellular creatine levels than seen in control cells). The accumulation of high levels of cre atine affected [H-3]creatine uptake by decreasing the V-max for transport. High intracellular creatine levels were maintained in the absence of extrac ellular creatine. External creatine stimulated the release of stored creati ne by an exchange mechanism dependent on extracellular Na+. These studies h ave shown that cellular creatine levels can be affected by the amount of cr eatine transporter in the membrane and exchange through the creatine transp orter. These findings highlight the importance of the creatine transporter in the maintenance of intracellular creatine levels. (C) 1999 Elsevier Scie nce B.V. All rights reserved.