ZONE ELECTROPHORESIS IN THE PREPARATION OF SERUM AND PITUITARY EXTRACTS FOR BIOASSAY OF THYROID STIMULATING HORMONE1

Abstract

Using zone electrophoresis in a starch-supported phosphate buffer medium at pH 7.4, and a chick I131 uptake assay for TSH, it was shown that: thyroid stimulating activity of a partially purified commercial beef TSH preparation is associated with the protein peak and is transported primarily with the gamma-globulins of human serum when added in vitro. There is clear cut separation between the I containing fraction of serum or thyroxine and exogenous TSH. Inhibition of the manifest efficacy of TSH by thyroxine is reversible by electrophoresis and does not imply structural alteration of the TSH. The observed differences in transport of beef TSH and thyroxine probably also apply to human pituitary TSH. Beef TSH preparations and human crude pituitary extract display comparable fractions which inhibit the end point in the bioassay. Fractionation of human sera reveals a non- iodine containing inhibitor of the augmented uptake of I131 in response to beef TSH in some sera but does not uncover endogenous TSH.