IMMUNOCYTOCHEMICAL LOCALIZATION OF THE RENAL NEUTRAL AND BASIC-AMINO-ACID TRANSPORTER IN RAT ADRENAL-GLAND, BRAIN-STEM, AND SPINAL-CORD

A neutral and basic amino acid transporter (NBAT) cloned from rat kidn ey was recently localized to enteroendocrine cells and enteric neurons . We used an antibody directed against a synthetic peptide representin g a putative extracellular domain of NBAT to determine whether this tr ansporter was also present in other endocrine and neural tissues, incl uding rat adrenal gland, brainstem, and spinal cord. Abundant, highly granular labeling for NBAT was observed in the cytoplasm of chromaffin and ganglion cells in the adrenal medulla. A small population of inte nsely labeled varicose processes was also seen in both the cortex and the medulla of the adrenal gland. More numerous, intensely labeled var icose processes were detected in brainstem and spinal cord nuclei, inc luding the locus coeruleus, rostral ventrolateral medulla, nuclei of t he solitary tract, dorsal motor nucleus of the vagus, and intermediola teral cell column of the thoracic spinal cord. Significant perikaryal labeling for NBAT was only detected in brainstem and spinal cord follo wing intraventricular colchicine treatment, which increased the number , distribution, and intensity of NBAT-immunolabeled cells. These NBAT- immunoreactive perikarya were most numerous in the locus coeruleus, ro stral ventrolateral medulla, nuclei of the solitary tract, and raphe n uclei. Ultrastructural examination of the nuclei of the solitary tract of normal rats showed that NBAT was localized predominantly to axon t erminals. Within these labeled terminals, NBAT was associated with lar ge dense core vesicles and discrete segments of plasma membrane. The o bserved localization of NBAT suggests that this renal specific amino a cid transporter subserves a role as a vesicular or plasmalemmal transp orter in monoamine-containing cells, including chromaffin cells and au tonomic neurons. (C) 1995 Wiley-Liss, Inc.