THE EFFECT OF THYROXIN AND THYROTROPIC HORMONE ON LIVER AND KIDNEY TISSUE RESPIRATION OF RATS OF VARIOUS AGES1

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Abstract
In 2 age series of rate of both sexes from 2 to 12 mos. of age, (a) fasted 18 to 24 hrs., (b) fasted 42 to 48 hrs;, the effects of thyroxin, injected for 6 days previously, on liver and kidney tissue metabolism were studied by the Warburg method, using the Marsh flask. [female] tissues after longer fasting maintained metabolism through the age range better than [male]. Longer fasting reduced the R. Q. in liver often to 0.48, in kidney only to 0.80. The significance of the low liver R. Q.''s is discussed. Thyroxin produced an increasing hypermetabolism of liver tissue with age to the region of 30 to 35% after 6 to 8 mos. It produced a generally diminishing effect with age in kidney of [male][male], but a sustained (a) or increasing (b) effect in kidney of [female][female]. Thyrotrophic hormone was administered for 6 days only in (b) series. It produced a generally increasing hypermetabolism with age in both sexes, which, from the dosage used, reached a level of only 20% in liver and 10% in kidney tissue. The peak was reached earlier in [male] liver (6 mos.) than in [female] (12 mos.). In kidney it came at the same age (12 mos.) in both sexes. A single group of 18-month-old [female][female] showed a high or maximal effect of thyroxin but a lesser effect of thyrotrophic hormone than did the 12-mo.-old group. Neither hormone changed the R. Q. of either tissue at any age.