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  • Title: Up-regulation of insulin receptors in rat liver plasma membranes.
    Author: Corin RE, Donner DB.
    Journal: J Biol Chem; 1981 Nov 25; 256(22):11413-6. PubMed ID: 7028732.
    Abstract:
    Kinetic experiments (uptake versus time) were utilized to examine the effects of occupancy on insulin receptor availability in rat liver plasma membranes in vitro. The following observations were made: 1) at 4 degrees C, a 3-h exposure of membranes to 100 nM native insulin, followed by removal of unbound hormone, resulted in a subsequent decrease of 125I-insulin binding at 4 degrees C. In a similar experiment at 23 degrees C, no decrease of 125I-insulin binding was observed. 2) At 23 degrees C, 131I-insulin (5 nM) was bound to membranes in a slowly reversible manner after a 3-h association. After removal of free hormone, the 131I-insulin-treated membranes displayed similar binding of 125I-insulin (1 nM) relative to controls despite persistent high level occupancy of receptors by 131I-insulin. 3) At 23 degrees C, phospholipase pretreatment of membranes enhanced 125I-insulin uptake (approximately 40%). Phospholipase-digested membranes exposed to 100 nM native insulin for 3 h bound more 125I-insulin (approximately 40%) than did nondigested membranes preincubated without native insulin. The results allowed speculation that rat liver membranes up-regulated insulin receptors after treatment with insulin and that this was mediated by exposure of cryptic binding sites.
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