Effect of Thyroxin on Formation of Sugar in Surviving Liver of Winter Frog.

Abstract

This study was made upon the perfused liver of the bullfrog (Rana catesbiana). It was found that in the isolated livers, whether excised or left in situ, thyroxin as a rule produced a slight fall in the amount of sugar given off into the perfusate, as against the amounts of sugar obtained during the preliminary control periods.

When the body of the frog was perfused with thyroxin through the systemic aorta there was a marked rise in the sugar of the perfusate draining from the hepatic vein. (Graph 1.) This increase lasted only a limited length of time and was then followed by a gradual decline of the sugar concentration to the control level. The fall occurred in spite of prolonged perfusion with thyroxin. The same results were observed in a frog with the adrenals excluded from the circulation.

When the liver was tied off so that it could be perfused separately from the body, and the body perfusates, collected from the posterior vena cava, were passed through the isolated organ, there was a sharp and prolonged increase in the hepatic sugar. There was no further rise, however, as a result of perfusion with body perfusate which had thyroxin added to it before passing it through the body. In an experiment with 2 frogs which were cross-perfused, the fluid from the vena cava of the one frog emptying through a rubber tube connection into the liver of the other, there was a 22% rise in the hepatic sugar. At the end of the experiment this liver was found to contain only 6.10 mg. of glycogen.

These results seem to point to the conclusion that the effect of thyroxin upon the carbohydrate of the liver is probably an indirect one. The manner in which this influence is brought about is not yet clear.