Specific and functional insulin receptors in rat renal papilla.
To investigate a possible action of insulin on the rat kidney papilla, the binding of 125I-insulin to papilla microsomes was examined. This binding was specific to insulin in that it was displaced by increasing concentrations of unlabelled porcine insulin and to a lesser extent by porcine proinsulin and IGF-I, but not by IGF-II and bGH. Scatchard plot of the binding data was curvilinear consistent with either two classes of receptors with different affinities or a single class of receptors that showed negative cooperativity. A small fraction of 125I-insulin (maximum 2%) was degraded during incubation, but with a Km two order of magnitude higher than the constant of affinity for binding. Insulin stimulates the incorporation of phosphate to phosphatidylcholine in a dose-dependent manner, reaching a maximum with 10 nM insulin. This data showed both the presence of specific insulin receptors in the kidney papilla and an insulin action through the synthesis of phospholipids by insulin.
Balbis
A
A
Departamento de Quimica Biológica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina.
Setton-Avruj
C P
CP
Sterin-Speziale
N B
NB
Turyn
D
D
D000818:Animals; D001667:Binding, Competitive; D007328:Insulin / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D007457:Iodine Radioisotopes; D007679:Kidney Medulla / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008861:Microsomes / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism; D010761:Phosphorus Radioisotopes; D011384:Proinsulin / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011972:Receptor, Insulin / Q000502:physiology*
D007328:Insulin; D007457:Iodine Radioisotopes; D010710:Phosphates; D010713:Phosphatidylcholines; D010761:Phosphorus Radioisotopes; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D011384:Proinsulin; D011972:Receptor, Insulin