GABA transport and subcellular distribution in the rat anterior pituitary gland

In this investigation we have studied the uptake of gamma aminobutyric acid (GABA) into anterior pituitary slices. Tissue:medium ratios of about 45:1 were obtained after a 30-min incubation. The process responsible for 3H-GABA uptake was temperature-sensitive and sodium-dependent. The kinetic constants of saturable GABA transport were: Km 4.141 microM and Vmax 0.973 pmol/min/mg protein, at 25 degrees C. The incorporation of GABA into anterior pituitary was inhibited by specific inhibitors of neuronal and/or glial uptake. The subcellular distribution of GABA was investigated by continuous sucrose density gradients and differential centrifugation. Most of the endogenous and labelled GABA was present in the soluble fraction. However, a small part of GABA was found in the particulate fraction. These observations indicate that the anterior pituitary gland is able to concentrate GABA which interacts with intracellular particles.