The phospholipid base-exchange system as a possible modulator of γ-aminobutyric acid transport in brain cells.

Mixed cell suspensions from rabbit brain have been used to study the effect of base exchange in membrane phospholipids, on amino acid accumulation in vitro. γ-Aminobutyric acid (GABA), glutamic acid, and aminoisobutyric acid have been used. The accumulation of [(3)H]GABA, at concentrations employing the high-affinity uptake system, was measured after base-exchange reactions with ethanolamine, choline, orL-serine. Serine incorporation induced an increase of GABA uptake at all the concentrations used, while choline incorporation essentially led to inhibition of GABA accumulation. Ethanolamine exchange produced both stimulation and inhibition. The observed effects were not specific for GABA. Neuronal and glial cell perikarya and synaptosomes were studied in the same system in an attempt to resolve the complex type of response obtained with the mixed suspension. Cell specificity was found with respect to stimulation or inhibition of GABA transport after base exchange but, in some cases, the isolated fractions retained the multiphasic response observed with the mixed suspension.