RELATIONSHIP BETWEEN RESTING METABOLISM AND HEPATIC-METABOLISM - EFFECT OF HYPOTHYROIDISM AND 24 HOURS FASTING

In this paper, we have examined the relationship between the changes i n the resting metabolic rate (RMR) and the changes in hepatic metaboli sm induced by hypothyroidism and 24 h fasting. The results show that h ypothyroidsm induces a significant decrease in RMR, while 24 h fasting reduces RMR in euthyroid but not in hypothyroid rats. We have also me asured oxygen consumption in isolated hepatocytes from euthyroid and h ypothyroid rats, fed or fasted for 24 h. The results show that hypothy roidism is characterized by reduced hepatic oxygen consumption. On the other hand, 24 h fasting induces an increase in oxygen consumption in both euthyroid and hypothyroid rat liver cells, although the respirat ory rates of hypothyroid rats were lower than those of euthyroid rats. The above findings, as a whole, show that hypothyroidism and 24 h fas ting have similar effects on RMR but opposite effects on hepatic metab olism. In addition, a normal thyroid state does not appear to be neces sary for the observed changes in hepatic metabolism due to 24 h fastin g.