Uptake of GABA by bovine adrenal medulla slices.

A sodium dependent GABA uptake system has been found in bovine adrenal medulla slices. This uptake has a Km of 83.19 +/- 38.45 microM and a Vmax of 9.20 +/- 1.36 pmol/min X mg of tissue. It was inhibited by nipecotic acid and 2,4-diaminobutyric acid (IC50 67 and 38.5 microM, respectively) but not by beta-alanine at concentrations up to 5 mM, a result which is similar to those found for the neuronal GABA uptake rather than the glial uptake. It is suggested that GABA uptake together with catabolic action of GABA-transaminase, also found in this tissue, could be regulating the GABA levels disposable for the proposed modulator role on catecholamine secretion of this amino acid in adrenal medulla.