Abstract
Plasma membrane preparations were isolated from mononuclear leukocytes obtained from 18 children with IDDM (insulin-dependent diabetes mellitus), 9 healthy children, and 8 normal adults.Their β-adrenergic receptor (β-receptor) was studied using 125I-iodohydroxybenzylpindolol (125I-IHYP) as a radioligand. The β-receptor densiy in the mononuclear leukocytes of the IDDM patients was found to be decreased (Bmax = 27.6 ± 2.0 fmol 125I-IHYP/mg protein : mean ± SE) compared with those of normal children (40.4 ± 3.5) and normal adults (36.9 ± 2.1), while no significant difference was seen in the density between normal children and adults. There were no significant differences in the binding affinities among those groups. When the IDDM patients were divided into groups on the basis of their blood glycosylated hemoglobin (HbAl) levels, group B patients (HbAl≥10%, n=9) had smaller receptor densities in the leukocytes than group A patients (HbAl<10%, n=9). In IDDM patients, a negative correlation was found between the receptor density and blood levels of glucose or HbAl, while no correlation was observed between the receptor density and plasma catecholamines, free insulin or glucagon.
As group B patients had high blood levels of both HbAl and glucose, the decrease in the recepter density might be a homeostatic response for restoring the poorly-controlled hyperglycemic state to normoglycemia.
