Calmodulin in rat incisor secretory ameloblasts as revealed by protein A-gold immunocytochemistry

Thin sections of aldehyde-fixed, undecalcified, embedded rat incisor enamel organ were incubated with sheep antiserum to bovine testes calmodulin to reveal the sites of antigen-antibody reaction at the ultrastructural level in secretory ameloblasts using the protein A-gold immunocytochemical technique. Specific immunolabelling was localized intensely on free polyribosomes and those attached to rough-surfaced endoplasmic reticulum but only rarely observed in the cisternal space. The nuclei, mitochondria, cytosol, and plasma membranes were also immunoreactive. The Golgi membranes and related vesicles, secretion granules, and lysosomes were unlabelled. The proximal and distal cell web junctional complex systems were not immunoreactive. These findings suggest that calmodulin location reflects its synthetic site and multifunctional roles in the immunolabelled cytoplasmic components of secretory ameloblasts.