Abstract
We previously reported that rat adrenal chromaffin cells contained GABA which may play a paracrine or autocrine role. The fractional study of bovine adrenal medullae indicates that GABA is recovered in fractions with low density (corresponding to 10-15% sucrose) but not those with high density (50-65%), whereas dopamine-β-hydroxylase was detected in both fractions, suggesting that chromaffin granules are heterogeneous in terms of GABA contents. In the present study, this notion was morphologically examined in rat chromaffin cells and PC12 cells by immunocytochemical methods and immunoelectron microscopy. Immunocytochemistry with anti-vesicular GABA transporter (VGAT) antibodies showed dot-like staining in the cytoplasm, which was partially co-localized with chromogranin A-like immunoreactivity, a marker of chromaffin granule. Synaptophysin-like immunoreactivity, a marker of synaptic-like vesicle, was also detected in the cytoplasm and it did not seem to be co-localized with VGAT or chromogranin A-like immunoreactivity. The immunostaining of endogenous VGAT in PC12 cells also partly coincided with that of chromogranin A, but not that of synaptophysin. These results demonstrate that in adrenal chromaffin cell, GABA is accumulated in chromaffin granules but not in synaptic-like vesicles and support that chromaffin granules are heterogeneous: one group of granules contains GABA; the other does not. Fine localization of VGAT in chromaffin cells by immunoelectron microscopy will be shown and more details of GABA-containing vesicles will be discussed. [J Physiol Sci. 2008;58 Suppl:S199]
