Reciprocal modulation of insulin and insulin-like growth factor-I receptor affinity by calcium |
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Authors: | R C Baxter P F Williams |
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Institution: | Department of Endocrinology, Royal Prince Alfred Hospital, Sydney, NSW 2050, Australia |
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Abstract: | In contrast to its stimulation of insulin binding to human placental membranes, calcium inhibited the binding of insulin-like growth factor-I. The effects on receptors for both peptides were half-maximal at 2 mM calcium, and were entirely due to alterations in high affinity binding sites for the respective ligands. Calcium decreased the affinity of insulin-like growth factor-I sites, while stimulating the expression of high affinity insulin sites. Competition by each peptide at the receptor for the other peptide was enhanced by calcium. Modulation by calcium might provide a mechanism to amplify functional differences between the two structurally similar receptors. |
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