Insulin receptor studies of erythrocytes and mononuclear leucocytes in phasic insulin diabetes mellitus.

This study was designed to investigate any differences in cellular binding of insulin between phasic insulin-dependent (malnutrition-related) diabetes mellitus (PIDDM) and insulin-dependent, non-insulin-dependent, and normal controls. Isolated, washed red and white blood cells obtained after 12-14 hr fast, were separately incubated with varying concentrations of non-radioactive insulin, and a fixed quantity of radioactively labelled insulin. After the 3-hr incubation, cells were washed with buffer, and radioactivity determined on an autogamma counter. Percentage binding, receptor sites number and affinity were all determined by linear regression of the Scatchard plot. Fasting plasma insulin and glucose levels were also assayed. The results obtained show decreased binding of insulin in red blood cells [11.3 +/- 1.3%) and white blood cells 2.9 +/- 0.5%) in PIDDM. This was due to decreased receptor sites (red blood cells 39 +/- 11; white blood cells 0.5 +/- 0.11 x 10(4] as well as decreased affinity (red blood cells 0.14 +/- 0.03 x 10(9) M-1; white blood cells 0.17 +/- 0.04 x 10(9) M-1) when compared to the normal and diabetic (both insulin and non-insulin-dependent) controls. Phasic insulin-dependent diabetes (malnutrition-related diabetes mellitus) is characterized by decreased red and white cellular binding to insulin, in addition to decreased production of insulin.