Tadao Ishii

Comparison of thyroxine-binding plasma proteins of various vertebrates and their evolutionary aspects.

Abstract The patterns and the binding capacities of thyroxine-binding plasma proteins in various species of vertebrates were compared, and their evolutionary aspects were considered. Protein association of radioactivity in plasma-radioactive thyroxine mixtures was characterized by use of a radioautographic technique after cellulose acetate electrophoresis. Thyroxine-binding capacity of alpha-globulin was determined after adding carrier l -thyroxine to the plasma of the test animals: In Primates, prealbumin, albumin, and alpha-globulin-bound thyroxine; in cattle, albumin, post-albumin, and alpha-globulin-bound thyroxine; in other Artiodactyla, i.e., goats, sheep, muntjak deer, and swine, albumin- and alpha-globulin-bound thyroxine. In the Artiodactylas, the thyroxine-binding capacity by alpha-globulin was high compared with other orders of Mammalia and the lower classes of vertebrates. In horses and dogs, most radiothyroxine was bound to albumin and a relatively smaller amount of radioactivity was found in alpha-globulin. In cats and rabbits, the presence of thyroxine-binding alpha-globulin was questionable, and relatively strong binding of radiothyroxine was found in post-albumin and albumin. No apparent thyroxine-binding alpha-globulin was detectable in Rodentia. Bound radioactivity was found only in plasma albumin in guinea pigs, but in mice both in albumin and post-albumin. In rats, most radiothyroxine was bound to albumin and a very little amount of radioactivity was found in postalbumin. In lower vertebrates such as Aves, Reptilia, Amphibia, and Pisces, no thyroxine-binding alpha-globulin was found. Radiothyroxine concentrated in plasma albumin in some species (chicken, duck, caiman, fish), but in other species (pigeon, snake, lizard, tortoise, frog, newt), the radiothyroxine concentrated both in albumin and pre-albumin.

A procedure for the determination of plasma thyroxine in farm animals

ラジオステレオアッセイ法による家畜の血漿中サイロキシン測定を行なうため,抽出条件の検討を行ない次の結論を得た.1) 血漿中サイロキシンの抽出溶媒としては,アルコールとケトンの類が優れているが,なかでも蛋白凝固力,蒸発除去の難易などを考慮すると血漿の2-3倍量のエタノール使用が最適である.2) 血漿に2倍量のエタノールを加えてサイロキシンを抽出した場合,抽出液にサイロキシン結合能を有する血漿蛋白質が混入した.この混入蛋白質が血漿中サイロキシン測定値を負にする主因と考えられる.3) 抽出液中の混入蛋白質は,抽出液を乾固後エタノールで再抽出する方法でほとんど除去され,サイロキシン結合能も失なわれる.すなわち,再抽出法によって蛋白質混入による血漿中サイロキシン測定値の低下は防止される.4) 抽出液の蒸発乾固によってはサイロキシンの散逸は起こらない.