May 10, 1976

Binding and degradation of insulin by human peripheral granulocytes. Demonstration of specific receptors with high affinity

The Journal of Biological Chemistry
R D FussgangerP De Meyts

Abstract

The interaction of insulin with human circulating granulocytes was studied with the use of 125I-insulin. Human granulocytes, isolated from blood by the Böyum technique, showed high insulin-degrading activity in vitro which almost obscured the presence of specific, high affinity binding sites. Degradation, measured by trichloroacetic acid precipitation and by binding to well characterized insulin receptors on cultured human lymphocytes (IM-9 line), was due to extracellular as well as cell-bound enzymes. Degradation was enhanced by Ca2+ and thiols and inhibited by various protease inhibitors and sulfhydryl-blocking reagents. Phenylmethylsulfonyl fluoride (5 X 10(-4) M), a serine protease inhibitor, was the most potent and inhibited 125I-insulin degradation by 80 to 90%. Tert-butyl hydroperoxide (2 X 10(-3) M), a glutathione-oxidizing reagent, inhibited degradation by 35 to 50%, possibly due to an effect on a glutathione-insulin transhydrogenase. Neither of the inhibitors affected cell viability. In the presence of inhibitors of degradation, binding sites for insulin with high affinity were detected, which by multiple criteria were true insulin receptors. Binding to these sites was rapid, saturable, and reversible with about 1000 ...Continue Reading

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Mentioned in this Paper

Glutathione-insulin transhydrogenase
Protease Inhibitors [MoA]
Extracellular
Enzymes, antithrombotic
Lymphocytes as Percentage of Blood Leukocytes (Lab Test)
Hormone Receptors, Cell Surface
Serine Proteinase Inhibitors
Granulocyte Count
Lymphoid Cells
P4HB

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