抄録
We have previously demonstrated that GABA system (GABAA receptors, GABA synthesizing enzyme, and vesicular GABA transporter) existed in rat adrenal medullae (AM) at mRNA and protein levels but not in adrenal cortical (AC) cells, and have conclude GABA may function as a paracrine or autocrine in AM cells. In the present study, we examined vesicles of bovine AM cells immunologically and morphologically with the sucrose density gradient and electron microscopy to identify which organelle contains GABA. The fractionation study showed that vesicular GABA transporter (VGAT), which was a necessary enzyme to accumulate GABA in vesicles from cytosol, was found mainly in the low density fractions (10 and 15%), while DβH, a marker protein of chromaffin granules, was presented in both low (10–25%) and high density fractions (50–65%) but not in the middle density fractions (30–45%) where synaptophysin, a marker protein of synaptic-like vesicles, was enriched. Catecholamine distribution over the sucrose gradient was nearly consistent with DβH distribution. EM study demonstrated that there was a difference in the size distribution of vesicles in different fractions. Fifteen percent and 60% fractions mainly contained granules with a median of diameter of 210 nm and 237 nm respectively while a 25% fraction contained synaptic-like vesicles with 189 nm. These results suggest that chromaffin granules are heterogeneous and GABA may be stored in chromaffin granules with a low density, but not in synaptic-like vesicles. [J Physiol Sci. 2007;57 Suppl:S172]
