Human circulating monocytes internalize 125I-insulin in a similar fashion to rat hepatocytes: relevance to receptor regulation in target and nontarget tissues.
Circulating monocytes bind 125I-insulin in a specific fashion and have been used to analyze the ambient receptor status in humans. When freshly isolated circulating monocytes are incubated with 125I-insulin and examined by electron microscopic autoradiography, approximately 18% of the labeled material is internalized after 15 minutes at 37 degrees C. By 2 hours at 37 degrees C, approximately one half of the 125I-insulin is internalized. Internalization occurs also at 15 degrees C but at a slower rate. Furthermore, the monocytes bind and internalize 125I-insulin in a manner that mirrors that of major target tissues, such as rat hepatocytes. These data suggest that the insulin receptor of the circulating monocyte might be regulated by adsorptive endocytosis in a manner analogous to that of target tissue, such as the liver.
Grunberger
G
G
Robert
A
A
Carpentier
J L
JL
Dayer
J M
JM
Roth
A
A
Stevenson
H C
HC
Orci
L
L
Gorden
P
P
D000818:Animals; D001345:Autoradiography; D002469:Cell Separation / Q000379:methods; D002498:Centrifugation; D002499:Centrifugation, Density Gradient; D005362:Ficoll; D006651:Histocytochemistry; D006801:Humans; D007457:Iodine Radioisotopes; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008854:Microscopy, Electron; D009000:Monocytes / Q000378:metabolism* / Q000648:ultrastructure; D011205:Povidone; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism*; D012822:Silicon Dioxide; D013696:Temperature
D007457:Iodine Radioisotopes; D005362:Ficoll; C016039:Percoll; D012822:Silicon Dioxide; D011972:Receptor, Insulin; D011205:Povidone