NUMERICAL-ANALYSIS REVEALS COMPLEXITIES OF GLUTAMATE TRANSPORT

The uptake of radiolabeled glutamate into cultured human (HeLa S3) and hamster (CHO-Kl) cells was analyzed according to modified Michaelis-M enten models fit by the Marquardt least-squares method. Kinetic parame ters not previously reported for these cells were obtained. Some rarel y used features available with this fitting method proved to be extrem ely helpful. Most importantly, a goodness-of-fit measure revealed a si gnificant alteration of glutamate uptake in HeLa cells that was induce d by starvation. This apparent regulation, unexpected for glutamate tr ansport, might have been missed if the fit had been judged by eye or b y the magnitude of parameter standard deviations. Techniques for analy zing parameter distributions, improving experimental design and perfor ming tests of significance are also described.