ERYTHROCYTE INSULIN-LIKE GROWTH-FACTOR-I RECEPTOR EVALUATION IN NORMAL SUBJECTS, ACROMEGALICS, AND GROWTH HORMONE-DEFICIENT AND INSULIN-DEPENDENT DIABETIC CHILDREN

Insulin-like growth factor-I (IGF-I) receptors are characterized in se veral animal and human tissues. IGF-I receptor studies performed in er ythrocytes to assess IGF-I receptor status at target-cell tissues are potentially useful for clinical studies, since tissue biopsies or cult ures are not required. However, validation of results is challenged by some investigators on the basis of discrepancies described in compara tive studies with other cell types, probably related to populations of different cell ages affecting binding to red blood cells (RBCs). By c orrecting cell age for creatine, we studied IGF-I receptor status in 2 4 normal subjects (11 adults and 13 children, eight prepubertal and fi ve pubertal) and 33 patients with pathologic conditions (five adult ac romegalics, six children with pituitary dwarfism, and 22 type I diabet ic children, 15 prepubertal and seven pubertal). Acromegalic patients with higher plasma IGF-I and insulin levels presented lower IGF-I spec ific binding ([B-o] mean +/- SEM, 6.1% +/- 0.8%) and affinity ([ED(50) ] 28.5 +/- 2.2 ng/mL) than normal adults (B-o, 10.9% +/- 0.7%; ED(50), 16.4 +/- 0.9 ng/mL; P < .001), and growth hormone (GH)-deficient chil dren showed higher IGF-I binding (24.6% +/- 1.7%, P < .001) without si gnificant affinity alterations than normal prepubertal children (B-o, 14.7% +/- 1.0%). Both prepubertal and pubertal type I diabetic childre n with higher GH levels presented decreased IGF-I binding (11.4% +/- 0 .9% for prepubertal, P < .05; 10.0% +/- 1.1% for pubertal, P < .05) to RBC receptors in comparison to the respective control group (14.7% +/ - 10% and 14.9% +/- 1.3%, prepubertal and pubertal, respectively). Whe reas in pubertal diabetics mean IGF-I basal levels were significantly reduced as compared with the respective controls, no difference was ob served in mean IGF-I basal levels in normal and diabetic prepubertal c hildren. Copyright (C) 1995 by W.B. Saunders Company