suchiya T

Thyroxine binding by albumins in bisalbuminemic serum

Because of discordant reports about thyroxine (T4) binding by 2 albumin fractions of bisalbuminemic serum, the binding of T4 by 2 albumin fractions was studied in sera of 5 subjects from 5 different families with this condition, following the fractionation of [131I]T4 labelled serum by electrophoresis on cellulose acetate membrane. The electrophoresis of serum demonstrated bisalbumin in all 5 subjects in barbital buffer but in only one of them in glycine acetate buffer. Two albumins of these sera were determined to consist of normal and slow-moving fractions by their electrophoretic mobility. The radioactivity of [131I]T4 added to sera was almost equally distributed in two fractions of albumins whenever two albumins were separable by electrophoresis. The calculated amount of T4 bound by unit gram of each fraction of albumin was in the range of 17.0 to 31.5 μg/g and was not different between two fractions of albumin in the individual subjects. The serum levels of thyroid hormones, T4, free T4, triiodothyronine (T3) and free T3 as well as that of T4-binding globulin capacity (TBGcap) were not different from the respective values of normal subjects. Findings appear to indicate that the presence of bisalbumin has no influence on serum concentrations of thyroid hormones and their serum protein binding.