Data on the transport of thyroxine-I-131 by the plasma proteins in various animal species

Abstract

The thyroxin circulates in conjunction with the albumin fraction and a fraction situated between the alpha-r and alpha-2 globulins (interalphaglobulin fraction, or Thyroxin binding protein, TBP), as has been observed by several authors (2, 4, 6) with electrophoresis on paper with a veronal tampon and radioactive thyroxin. INGBAR (3) showed how it is possible to perceive a third fraction which transport thyroxin, the prealbumin fraction, using a tampon of tris-maleate pH 8.6, for the veronal tampon inhibits the fixing of the thyroxin to the said protein.

Tn the present work we have analysed 22 serums of animals belonging to 7 spe­cies (bull, pig, sheep, goat, horse, rabbit and chicken) with the addition in vitro of thyroxin-F31, and, after an incubation period, electronhoresis on paper was carried out with a tris-maleate tampon. The radioactivitv of the strips of electro­ phoresis was determined by a Philips countage unit, and the corresponding autoradiographies were also obtained in this way. The strips are finally dved by the usual technique and are read on a densimeter.

In table I and figure i it will be seen how, in general, the alohaglobulin and albumin fractions act as transporters, and we have not been able to observe the presence of the prealbumin fraction, as has been pointed out in the monkey (7), and also in the duck and the npigeon (1,5). In the chicken only an albumin fraction has shown itself, and in the pig it cannot be determined to which protein fraction the radioactivity corresponds. In general it may be indi­cated that the tris maleate tampon pro­duces results noticeably inferior to those obtained with the veronal tampon as far as the differentiation between the plasmatic proteins is concerned.

The absence of the prealbumin frac­tion is discussed and an evaluation is made of the results in view of the few data obtained.