The mechanism of the calorigenic action of thyroid hormone. Stimulation of Na plus + K plus-activated adenosinetriphosphatase activity.
In an earlier study, we proposed that thyroid hormone stimulation of energy utilization by the Na(+) pump mediates the calorigenic response. In this study, the effects of triiodothyronine (T(3)) on total oxygen consumption (Q(OO2)), the ouabain-sensitive oxygen consumption [Q(OO2)(t)], and NaK-ATPase in liver, kidney, and cerebrum were measured. In liver, approximately 90% of the increase in Q(OO2) produced by T(3) in either thyroidectomized or euthyroid rats was attributable to the increase in Q(OO2)(t). In kidney, the increase in Q(OO2)(t) accounted for 29% of the increase in Q(OO2) in thyroidectomized and 46% of the increase in Q(OO2) in euthyroid rats. There was no demonstrable effect of T(3) in euthyroid rats on Q(OO2) or Q(OO2)(t) of cerebral slices. The effects of T(3) on NaK-ATPase activity in homogenates were as follows: In liver +81% from euthyroid rats and +54% from hypothyroid rats. In kidney, +21% from euthyroid rats and +69% from hypothyroid rats. T(3) in euthyroid rats produced no significant changes in NaK-ATPase or Mg-ATPase activity of cerebral homogenates. Liver plasma membrane fractions showed a 69% increase in NaK-ATPase and no significant changes in either Mg-ATPase or 5'-nucleotidase activities after T(3) injection. These results indicate that thyroid hormones stimulate NaK-ATPase activity differentially. This effect may account, at least in part, for the calorigenic effects of these hormones.
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology; D007668:Kidney / Q000201:enzymology / Q000378:metabolism; D008099:Liver / Q000201:enzymology / Q000378:metabolism; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects*; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D012964:Sodium / Q000378:metabolism*; D013961:Thyroid Gland / Q000502:physiology; D013965:Thyroidectomy; D014284:Triiodothyronine / Q000494:pharmacology*
D014284:Triiodothyronine; D010042:Ouabain; D012964:Sodium; D000251:Adenosine Triphosphatases; D011188:Potassium