Calbindin D‐27 kDa: preferential localization in non‐B islet cells of the rat pancreas

Abstract

The presence and abundance of calbindin in rat pancreatic islet cells was assessed by immunohistochemistry of either whole islets or purified B and non‐B islet cells, as well as by Western blotting of extracts derived from whole islets and purified B and non‐B islet cells. Immunohistochemistry of pancreatic sections indicated a higher calbindin content in non‐B cells, located at the periphery of the islets, than in the centrally located insulin‐producing B cells. Comparable results were obtained in purified islet cells. Likewise, scanning densitometry of the Western blots indicated that, relative to cell volume, the single calbindin band (Mr 27 kDa) was 5‐7 times higher in non‐B than in B cells. In the splenic lobe of chick pancreas, however, the opposite situation prevailed. Thus, insulin‐producing cells clustered in small roundish islets were more intensely labelled after exposure to anti‐calbindin serum than non‐B islet cells located in large and irregularly shaped islets. Nevertheless, even in the chick pancreas, non‐B islet cells contained an appreciable amount of calbindin.