Regional distribution of L-[methyl-14C] methionine (14C-MET) and 4-[18F] fluoro-antipyrine was compared using experimental rat tumors (AH109A) and a computerized autoradiogram image processor. Tissue distributions of the two tracers were found to be inhomogeneous in the tumor with nearly identical image patterns. Analysis of tissue radioactivities revealed that 82% of 14C-MET was derived from the acid insoluble fraction at 60 min after injection. The present study showed that 14C-MET uptake closely relates to tissue blood flow and may depend on its blood to tissue transport. Rapid incorporation of MET in the acid insoluble fraction implies that it is rapidly metabolized after transport into tumor tissue.
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