Diabetes is associated with a fall in serum levels of
insulin-like growth factor-1/
somatomedin-C (IGF-1/Sm-C) and a rise in
somatomedin inhibitor,
a factor which antagonizes
somatomedin action. We attempted to determine if the presence of
glucocorticoids was required for diabetes-related alterations in these circulating
growth factors. Diabetes was induced with
streptozotocin in intact or adrenalectomized rats. Adrenalectomized-nondiabetic and adrenalectomized-diabetic rats were given either no
glucocorticoids or daily
hydrocortisone acetate at 0.5 or 50 mg/kg
body weight, and killed 48 hours after
streptozotocin treatment. After serum fractionation via size exclusion high performance liquid chromatography (HPLC), IGF-1/Sm-C was determined by radioimmunoassay, and
somatomedin inhibitor by bioassay according to the ability of serum fractions to blunt cartilage stimulation by normal serum. Intact-diabetic rats had 22%
weight loss,
glucose 427 mg/dL, and
beta-hydroxybutyrate 7.2 mmol/L (all P less than .001 v control). Serum IGF-1/Sm-C levels in intact-diabetic rats were decreased 71%, while
somatomedin inhibitor rose to 470% of the control values (both P less than .004). Adrenalectomized-diabetic rats displayed comparable
hyperglycemia (greater than 400 mg/dL) and decline in IGF-1/SmC, with or without
glucocorticoid replacement. However, adrenalectomized-diabetic rats had greatly reduced
weight loss (10%),
beta-hydroxybutyrate (1.5 mmol/L), and
somatomedin inhibitor (59% of control), all P less than .01 v intact-diabetic.
Hydrocortisone 0.5 mg/kg in these animals increased
weight loss but had no significant effect on
beta-hydroxybutyrate or
somatomedin inhibitor levels.(ABSTRACT TRUNCATED AT 250 WORDS)