Transferrin (Tf) is the chief iron-transport protein in mammalian blood. Seventy-four diabetics 43 males and 31 females ranging in age from 14 to 79 yr were studied. In all cases, urine protein was negative, and Hb and liver function were normal.Serum fasting blood sugar (FBS), albumin, the integral IRI value after50gOGTT and Tf were measured.The Tf was estimated by laser immunoassay. There was no significant difference between the serum Tf levels of diabetic subjects and normal controls (287±43mg/dl vs.305±37mg/dl, mean±SD) However, the serum Tf levels in subjects with IDDM were significantly lower than those in the normal controls and subjects with NIDDM (249±41mg/dl vs.305±37, 299±36mg/dl;p<0.001). The serum Tf levels in diabetics were significantly correlated with the serum albumin levels (r=0.366, p<0.002, n=74), FBS (r=-0.338, p<0.02, n=55) and integral IRI values (r=0.608, p<0.002, n=25).
Rabbit anti-human thyroxine binding globulin (TBG) was precipitated with 50% ammonium sulfate, followed by passage through a DEAE-cellulose column.The immunoglobulin G (IgG) fraction so obtained was covalently attached to Sepharose CL-4B and used as an immunoadsorbent of serum TBG. After treatment with charcoal to remove endogenous thyroid hormones, 25ul of serum from5 healthy subjects was incubated with 125I-T3 andvarious concentrations of cold T3, 8-anilino-1-naphthalene sulf nic acid (ANS), tolbutamide, chlorpropamide and glibenclamide, followed by immunoadsorption with anti-TBG Sepharose. The binding of 125I-T3 was inhibited by cold T3 and ANS, whereas sulfonylurea drugs exerted no effect on the interaction between TBG and T3 at concentrations of between 2 and 200mg per dl of serum. These results, in contrast to the previous report of Hershman et al., suggest that sulfonylurea drugs at serum concentrations which would be expected from their daily therapeutic doses, do not affect the interaction between TBG and T3.