Abstract
In the course of a study of the influence of lactic acid upon tissue respiration it was observed that tissues from thyroidless rats showed a lower rate of oxygen consumption than did similar tissues from normal rats.
Bits of diaphragm tissue suspended in Ringer solution containing 0.2 per cent glucose and buffered to pH 7.5 by a M/80 phosphate mixture under an atmosphere of oxygen were studied by Warburg's 1 manometric method.
The results are of interest in connection with the recent paper of Grafe, Reinwein and Singer, 2 who found that the rates of respiration of surviving tissues of animals varying in size from the mouse to the ox, are of substantially the same magnitude, whereas the oxygen absorption per kilogram of the whole living animal is some 20 times greater for the mouse than for the ox, thus demonstrating that the constant relation between metabolism and surface area is a function of the intact animal, and not a result of inherent characteristics of the protoplasm. These authors seek an explanation in considerations of oxygen supply to the tissues and the relative number of patent capillaries. In the case of our thyroidless rats the metabolism of the living animal is 25 to 30 per cent below the average normal, as is also the respiration of its isolated tissues under conditions of maximum oxygen supply.
My thanks are due to Professor P. E. Smith, who gave me the thyroidectomized animals. Further work is in progress.
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