AJP - Gastrointestinal and Liver Physiology, Vol 240, Issue 1 69-G75, Copyright © 1981 by American Physiological Society
Insulin action in pancreatic acini from streptozotocin-treated rats. III. Electron microscope autoradiography of 125I-insulin
I. D. Goldfine, B. M. Kriz, K. Y. Wong, G. Hradek, A. L. Jones and J. A. Williams
Electron microscope autoradiographs were prepared from diabetic rat
pancreatic acini that had been incubated with 125I-insulin. Distribution
histograms of the distance of the 125I-insulin silver grains from the
nearest plasma membrane were prepared and compared with a histogram of an
125I line source. After 3 min of incubation, insulin was located
predominately on the plasma membrane, but even at this early time 15% of
the grains had an intracellular location. After 30 min of incubation, there
was a decrease in grains on the plasma membrane and an increase (to 45%) in
grains localized in the cell. At both times of incubation, a comparison of
the distribution of the insulin grains overlying subcellular organelles to
a theoretical random grain distribution pattern indicated that the
intracellular distribution of insulin grains was nonrandom. At 3 min, there
was a relative concentration of grains over the plasma membrane and
vesicles with an average diameter of 100 nm. At 30 min, there was a
concentration of grains over the plasma membrane, 100-nm vesicle, and
Golgi. These studies suggest that 125I-insulin is internalized into
pancreatic acinar cells in a time-dependent manner and then is nonrandomly
distributed inside the cell.
