Somatomedin in rat serum has been measured by a sensitive radioreceptor assay using
125I-labelled human somatomedin and human placental membrane. In rats made diabetic with
strepotzotocin, receptor-reactive somatomedin levels were decreased by up to 75%.
The decrease followed the time course of increasing serum glucose and occurred to
the same extent in rats aged between 4 and 40 weeks. Endogenous serum receptor-reactive
somatomedin appeared exclusively in high molecular weight fractions on gel chromatography.
In diabetes the decreased somatomedin was due to a fall in this high molecular weight
activity, but was not accompanied by a fall in somatomedin binding protein. These
results suggest a role for insulin in maintaining serum somatomedin levels.
Somatomedin - Radioreceptor Assay - Diabetes - Binding Protein
