Fig. 5. Immunogold localization of IP₃ receptors in isolated nuclei. Isolated nuclei from skeletal muscle cells were immunolabeled for type-1 or type-3 IP₃R with isoform-specific antibodies linked to 10 nm gold particles. (A) Type-1 IP₃R gold particles (indicated by arrows) located in the nuclear membrane mainly grouped in clusters. (B) Type-3 IP₃R labeling (indicated by arrows) is located in groups of particles in the nuclear membrane and the nucleoplasm. Inset, the nucleolus presents clusters associated with undefined structures. Bar, 100 nm.