A STUDY OF INSULIN RECEPTORS IN HUMAN MONONUCLEAR LEUCOCYTES

Abstract

Insulin [porcine] binding sites were demonstrated in human mononuclear leucocytes by a technique which includes isolation of mononuclear leucocytes from defibrinated blood and separation of cell bound and free [125I]insulin with silicone oil. Binding was time and temperature dependent. At 15.degree. C, equilibrium was reached after 90 min and a plateau maintained for at least 50 min. Incubations were carried out at 4.degree. C, 15.degree. C and 37.degree. C. Maximal binding was obtained at 15.degree. C. The optimum pH for insulin receptor interaction occurred at about 8. [125I]insulin binding to mononuclear leucocytes was a linear function of cell number concentration over a range of 17-70 .times. 106 .times. ml-1. The binding was a displaceable function of native insulin concentration. In a group of 21 young healthy persons with normal body weight a mean specific cell binding fraction of 1.92 .+-. 0.58 (s) .times. 10-2 was found. Analysis of the equilibrium between insulin and its receptor revealed an apparent heterogeneity of insulin receptors.