Receptors for insulin and epidermal growth factor: relation to synthesis of DNA in cultured rabbit lens epithelium. |
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Authors: | M D Hollenberg |
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Affiliation: | Division of Clinical Pharmacology, Department of Pharmacology and Experimental Therapeutics, and Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205 USA |
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Abstract: | Epidermal growth factor (EG factor) and insulin stimulate the incorporation of thymidine into contact-inhibited rabbit lens epithelial cells in culture. The maximal stimulation observed with EG factor is greater than with insulin. Half-maximal stimulation by EG factor is observed at 6 × 10?10m and for insulin at 1 × 10?9m. [125I]-labeled EG factor (2000 Ci/mmol, about 1 g atom of iodine per mol) is equipotent with native EG factor in stimulating DNA synthesis. Both insulin and EG factor bind to distinct high-affinity sites in intact lens cell monolayers; half-maximal binding is observed at about 10?9m for both polypeptides. A maximum of approximately 8 × 104 insulin molecules and 4 × 104 EG factor molecules are bound per cell. These observations indicate that cultured rabbit lens cells possess receptors for insulin and EG factor by biological and physicochemical criteria and raise the possibility that both peptides may play a role in lens growth and development. |
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