UPTAKE OF C14INTO THE BRAIN AND OTHER TISSUES OF NORMAL AND DYSTHYROIDAL MALE RATS AFTER INJECTION OF C14-L-GLUTAMINE

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Abstract
Uptake studies on whole plasma, brain and other tissues were performed at various time intervals after injection into euthyroid, hypothyroid and hyperthyroid male rats. The total uptake of C14 into whole tissue, bound-protein or TCA soluble (free amino acids) fractions was influenced by both dysthyroidal states. Chromatographic analysis of the TCA and bound-protein fractions of plasma and brain suggest that the metabolism of glutamine as reflected by its distribution between the free and bound-protein fractions was also influenced by both dysthyroidal states. The rather marked changes in plasma radioactivity as either glutamine or glutamic acid in relation to change in thyroid state were of considerable magnitude and suggest widespread disruption of normal glutamine metabolism throughout the body. Comparison of uptake of C14 -activity into the ventral horn motor neurons with other parts of the CNS [central nervous system] and other tissues revealed that these motor neurons take up considerably more of the labeled material on a per unit weight basis than any other single region of the CNS or of even any other organ of the body. The significance of this observation is discussed in relation to the "blood-brain barrier.".