Abstract
Employing a tequnique which determined the rotary Brownian motion by fluorescene polari- zation, an attempt was made to assay for blood thyroxine.
The principle of the method was briefly as follows. Fluorescent-labelled T-4 reacted with T4 with anti-T-4 fractionated to IgG, so that the weight of the molecules with fluorescence was con- siderably altered; this then resulted in a rotary Brownian motion. Fluorescene polarization was detected by FP analyzer (JIMCO Polarization Spectrofluorometer Model IBF-129)(Fig. 1).
By this method, a correlated relation ship between the alteration in fluorescence polarization and the concentration of thyroxine extracted from serum with methanol was obtained (Fig. 3).
A comparison was made between the assay levels obtained by the present method and the radioimmunoassay (Fig. 5). The specificity of the present method for T-4 was confirmed by examining the cross reactivity with tri, di and mono-iodothyronine (Fig. 4).
For clinical purpose, the present assay method requires only a small amount of serum (less than 100μl is available). The main advantage of our method is that the assay requires only simpleand rapid procedures as well as no use of radioisotope. The procedure of separation for T4 andanti-T-4 complex from free T-4 is eliminated.
