Immunocytochemical colocalizations of insulin, aromatic L-amino acid decarboxylase, dopamine beta-hydroxylase, S-100 protein and chromogranin A in B-cells of the chicken endocrine pancreas

Abstract

The colocalization of aromatic L-amino acid decarboxylase (AADC), dopamine beta-hydroxylase (DBH), S-100 protein and chromogranin A (CgA) in the insulin-containing B-cells of the chicken endocrine pancreas was investigated by using light microscopic immunohistochemistry and combined pre-embedding immunoperoxidase and post-embedding immunogold electron microscopic immunocytochemistry. Using the post-embedding method, immunoreactivity against the anti-insulin serum by protein A-gold technique was observed in the core of all types of B-cell granules. Immunoreaction with anti-S-100 protein serum was detected in the core of all types of B-cell granules from non-osmicated tissues even by post-embedding method, but immunoreactivities against the anti-AADC, DBH and CgA sera were only demonstrable in crystalloid granules of B-cells by pre-embedding method. Immunoreaction with the anti-CgA serum was also detected in the cytoplasmic matrix around crystalloid granules and also in the dense bodies showing immunonegative with anti-insulin serum. From these results, it seems likely that S-100 protein co-stored all types of B-cell granules involved in the maturation of granules, and AADC, DBH and CgA are related to the synthesis of noradrenaline in crystalloid granules of B-cells.