Insulin binding and insulin receptor tyrosine kinase activity are not altered in the liver of rats with non-insulin-dependent diabetes.
Using the insulin-glucose clamp technique, we have previously shown that an increased sensitivity to insulin in vivo is a characteristic of the liver in rats with non-insulin-dependent diabetes induced by neonatal streptozotocin administration. We have thus studied the properties of liver insulin receptor in that model. 125I-porcine insulin binding was found normal both in isolated plasma membranes and in solubilized, wheat germ agglutinin purified receptors prepared from livers of rats with non-insulin-dependent diabetes, when compared to controls. Basal and insulin-stimulated insulin receptor kinase activities were also found normal for both the autophosphorylation of the beta subunit of the insulin receptor and the phosphorylation of the artificial substrate poly (Glu-Tyr) 4:1. Thus, in that model of chronic insulin deficiency and mild hyperglycemia: 1) liver insulin receptors are not up-regulated; 2) tyrosine kinase activity remains unaffected. This last observation supports the hypothesis that the increased insulin effect in the liver of rats with non-insulin-dependent diabetes is probably distal to the insulin receptor kinase.
Kergoat
M
M
Lab. Physiol. Dev., CNRS UA 307, Université Paris 7, France.
Simon
J
J
Portha
B
B
D000818:Animals; D001345:Autoradiography; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D007328:Insulin / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011972:Receptor, Insulin
D007328:Insulin; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin