FURTHER OBSERVATIONS ON THE EFFECT OF THYROGLOBULIN AND THYROXIN ON THE O2CONSUMPTION OF TISSUES IN VITRO1

Abstract

Using a Warburg-Barcroft differential manometer system the effect of thyroglobulin and thyroxin upon the in vitro O2 consumption of guinea-pig kidnev. testis and heart was investigated. At lower levels of metabolism thyroglobulin stimulated the metabolism of each of these tissues. However, there appeared to be a "ceiling" above which thyroglobulin could no further elevate the O2 uptake, and this "ceiling" was higher, in the case of kidney and heart, in serum than in a salt buffer mixture. Thyroxin generally had no stimulating effect in either the salt buffer mixture or the serum. In 2 expts. in serum, however, a stimulating effect appeared, raising the possibility that thyroxin under certain circumstances may be made physiologically active by contact with serum.