Figure 4. Immunogold electron microscopy showing the localization of IP₃R1 in secretory granules in astrocytes.

Astrocytes from human brain tissues were immunolabeled for IP₃R1 (15 nm gold) with the affinity purified IP₃R1 antibody (A and B). The IP₃R1-labeling gold particles (indicated by arrows) were primarily localized in the membranes of secretory granules (SG) with some in the endoplasmic reticulum (see A), but not in the mitochondria (M). In the control experiments without the primary antibody no gold particles were seen in secretory granules (not shown). fm, filament. Bar = 200 nm.