Binding of [125I]insulin to specific receptors and stimulation of nucleotide incorporation in cells cultured from rat brain.
The occurrence of insulin receptors and biological responses to insulin has been investigated in trypsin-dissociated fetal rat brain cells maintained in culture for 8 days. Binding of [125I]insulin to brain cells in culture was time- and pH-dependent and 85--90% specific. Porcine insulin competed for [125I]insulin binding in a dose-dependent manner. Unrelated polypeptides, including angiotensin II, glucagon, bovine growth hormone, and bovine prolactin did not compete for [125I]insulin binding. The half-life of [125I]insulin dissociation from receptors at 24 degrees C was 15 min and a plot of In[B/Bo] vs time suggested two dissociated rate constants of 2.7 X 10(-4) sec-1 and 5.0 X 10(-5) sec-1. Scatchard analysis of the binding data gave a curvilinear plot which may indicate negative cooperativity or the occurrence of both high affinity (Ka = 2 X 10(11) M-1) and low affinity (Ka = 4 X 10(10) M-1) sites. Of the estimated total of 4.9 X 10(4) binding sites per cell, 28--30% appear to be high affinity sites. Incubation of cultures with insulin caused a time- and dose-dependent stimulation of [3H]thymidine and [3H]uridine incorporation into TCA-precipitable material. Maximum stimulation of thymidine incorporation (2--5-fold) occurred 11 h after incubation with 167 nM insulin. The same concentration of insulin caused a 2.2-fold increase in [3H]uridine incorporation in 2 h. These results indicate that cells cultured from rat brain contain specific insulin receptors capable of mediating effects of insulin on macromolecular synthesis in the central nervous system.
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D005333:Fetus; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology*; D007700:Kinetics; D012313:RNA / Q000096:biosynthesis; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism*; D014529:Uridine / Q000378:metabolism*
D007328:Insulin; D012313:RNA; D004247:DNA; D011972:Receptor, Insulin; D013936:Thymidine; D014529:Uridine