The uptake and metabolism of L-glutamate by tissue slices of the cestode Hymenolepis diminuta.

The in vitro uptake of L-[3H]glutamate by tissue slices of the cestode Hymenolepis diminuta, denuded of tegument, was investigated. Two sodium concentration-dependent mechanisms, one of high affinity (Kt 1.8 X 10(-5) M; Vmax 4.76 pMoles/min/mg wet weight) and another of low affinity (Kt 2.2 X 10(-4) M; Vmax 50.7 pMoles/min/mg wet weight), were identified, in addition to a sodium insensitive component. Exchange of preloaded [3H]glutamate did not occur in tissue slices incubated in dilute unlabelled glutamate. Acidic amino acids, imipramine and fluoxetine were effective inhibitors of high and low affinity uptake, while glutamate receptor ligands, neurotransmitters and some antihelminthics generally were not. The concentrations present in, and the metabolism of glutamate by, tissue slices was examined by HPLC. The significance of the three modes of glutamate uptake and their possible role in the physiology of H. diminuta are discussed.