Insulin action in pancreatic acini from streptozotocin-treated rats. III. Electron microscope autoradiography of 125I-insulin.
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.
D000818:Animals; D001345:Autoradiography; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D007328:Insulin / Q000502:physiology*; D008297:Male; D008854:Microscopy, Electron; D009940:Organoids / Q000378:metabolism; D010179:Pancreas / Q000503:physiopathology*; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism*
D007328:Insulin; D011972:Receptor, Insulin