DIANGOSTIC OF IGF-1 INDUCTION IN GROWTH RETARDED CHILDREN: CHANGES OF IGF-1 RECEPTOR NUMBER AND BINDING AFFINITY AFTER 5 DAYS GH ADMINISTRATION

Abstract

The acute response of IGF-1 to GH treatment (5 days, 0.1 E/kg per day) has been tested in seven children with growth retardation. All chlldrens have a normal GH-stimulation . With the change of the IGF-1 level after GH administration we tested the change of the IGF-1 receptor number and -affinity on the isolated lymphocytes of these patients. The IGF-1 level raised from 102 ± 57 ng/ml to 180 ± 94 ng/ml ≙ 186 + 65 %. In 5 patients there was no significant change in receptor affinity (from 0.47 ± 0.33 × 109 M−1 to 0.45 ± 0.31 × 109 M−1). Two subjects had a stimulation of receptor affinity from 0.28 ± 0.1 to 0.48 ± 0.15 · 109 M−1. The receptor number from 6 patients however decreased from 7282 ± 3309 to 4926 + 2538. This decrease was strongly correlated to the increase of the IGF-1 level (r= 0.94). One patient had an increase of receptor number from 2500 to 4980. Our results are corresponding with the suggestion of Rosenfeld et al (1982), that the downregulation of IGF-1 binding is accounted by a decrease in receptor number rather than change in binding affinity. It has to be discussed whether GH itself has an influence of increase of receptor affinity ( 2 patients) or receptor number ( 1 patient ). R.G. Rosenfeld et al (1982) Diabetes 31:375