Insulinlike growth factor I receptors in rabbit gastrointestinal tract. Characterization and autoradiographic localization.
Insulinlike growth factor I is a potent mitogen with insulinlike metabolic effects. Insulinlike growth factor I is synthesized in the liver, intestine, and other organs. Insulinlike growth factor I receptors are widely distributed and structurally similar to insulin receptors. Frozen sections of rabbit gastrointestinal tract were incubated in buffer containing 40 pmol/L [125I]insulinlike growth factor I. Binding was saturable, temperature- and time-dependent, and reversible. Saturation binding experiments showed a single class of high-affinity receptors (Kd = 0.9 nmol/L, Bmax = 0.36 pmol/mg protein). The IC50s for insulinlike growth factor I and insulinlike growth factor II were 3 nmol/L and 90 nmol/L, respectively; whereas insulin at 1-3 mumol/L displaced 50% of specific binding. Autoradiography of insulinlike growth factor I binding demonstrated significant differences in receptor density in gastrointestinal smooth muscle, epithelium of the esophagus, stomach, small intestine, and colon. These results indicate that a single class of specific, high-affinity insulinlike growth factor I receptors were distributed in muscular and mucosal layers of the entire rabbit gastrointestinal tract. Insulinlike growth factor I is likely to be an important local mediator of intestinal growth and metabolism.
Termanini
B
B
Medical and Surgical Service, Veterans Administration Medical Center, Washington, D.C.
Nardi
R V
RV
Finan
T M
TM
Parikh
I
I
Korman
L Y
LY
D000818:Animals; D001345:Autoradiography; D002851:Chromatography, High Pressure Liquid; D046508:Culture Techniques; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000648:ultrastructure*; D009130:Muscle, Smooth / Q000648:ultrastructure; D011817:Rabbits; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000378:metabolism*; D013627:Talc / Q000378:metabolism
D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins; D013627:Talc; D007334:Insulin-Like Growth Factor I