Thyroid hormone and cardiac function in mice deficient in thyroid hormone receptor- or - : an echocardiograph study

Weiss, Roy E., Claudia Korcarz, Olivier Chassande, Kevin Cua, Peter M. Sadow, Eugene Koo, Jacques Samarut, and Roberto Lang. Thyroid hormone and cardiac function in mice deficient in thyroid hormone receptoror : an echocardiograph study. Am J Physiol Endocrinol Metab 283: E428–E435, 2002; 10.1152/ajpendo.00019. 2002.—We investigated the effect of thyroid hormone (TH) receptor (TR) and isoforms in TH action in the heart. Noninvasive echocardiographic measurements were made in mice homozygous for disruption of TR (TR 0/0) or TR (TR / ). Mice were studied at baseline, 4 wk after TH deprivation (using a low-iodine diet containing propylthiouracil), and after 4-wk treatment with TH. Baseline heart rates (HR) were similar in wild-type (WT) and TR 0/0 mice but were greater in TR / mice. With TH deprivation, HR decreased 49% in WT and 37% in TR / mice and decreased only 5% in TR 0/0 mice from baseline, whereas HR increased in all genotypes with TH treatment. Cardiac output (CO) and cardiac index (CI) in WT mice decreased ( 31 and 32%, respectively) with TH deprivation and increased ( 69 and 35%, respectively) with TH treatment. The effects of CO and CI were blunted with TH withdrawal in both TR 0/0 ( 8 and 2%, respectively) and TR / mice ( 17 and 18%, respectively). Treatment with TH resulted in a 64% increase in LV mass in WT and a 44% increase in TR 0/0 mice but only a 6% increase in TR / mice (ANOVA P 0.05). Taken together, these data suggest that TR and TR play different roles in the physiology of TH action on the heart.