We immunohistochemically examined the distribution of glucokinase (GK) in t
he B-cells of pancreatic islets of normal rats. GK was stained punctately i
n the cytoplasm of B-cells when examined under the light microscope. By use
of a double-immunostaining technique, most of the GK immunoreactivity was
observed to bie colocalized with insulin immunoreactivity. Electron microsc
opic examination by the immunogold method revealed that GK immunoreactivity
was predominantly located within insulin-secretory granules of pancreatic
B-cells.