Bovine Chromaffin Cells Have Insulin‐Like Growth Factor‐I (IGF‐I) Receptors: IGF‐I Enhances Catecholamine Secretion

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Abstract
The binding of 125I‐insulin‐like growth factor‐I (125I‐IGF‐I) to bovine chromaffin cells was measured. Chromaffin cell cultures contained 111,000 ± 40,000 IGF‐I binding sites/cell. These sites bound IGF‐I with a KD of 1.1 ± 0.3 nM and had a much lower affinity for insulin. Cross‐linking studies showed that 125I‐IGF‐I bound to a protein that had an Mr of ∼ 125,000, similar to the Mr of the α subunit of the IGF‐I receptor in other tissues. Cells cultured with IGF‐I (10 nM) for 4 days exhibited an almost twofold increase in high K+‐evoked catecholamine secretion. Insulin was much less potent than IGF‐I in enhancing catecholamine secretion. These data indicate that binding of IGF‐I to its receptors on chromaffin cells can modulate the function of these cells.