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

We investigated the effect of thyroid hormone (TH) receptor (TR)alpha and -beta isoforms in TH action in the heart. Noninvasive echocardiographic measurements were made in mice homozygous for disruption of TRalpha (TRalpha(0/0)) or TRbeta (TRbeta(-/-)). Mice were studied at baseline, 4 wk after TH deprivation (using a low-iodine diet containing propylthiouracil), and after 4-wk treatment with TH.

Type 1 iodothyronine deiodinase in the house musk shrew (Suncus murinus, Insectivora: Soricidae): cloning and characterization of complementary DNA, unique tissue distribution and regulation by T(3).

The house musk shrew Suncus murinus (Insectivora: Soricidae) has been reported as having low thyroxine to 3,3'5-triiodothyronine (T(3)) converting activity in liver and kidney homogenates and was assumed to be type 1 iodothyronine deiodinase (D1)-deficient. To study whether this is due to structural abnormality of shrew D1, we cloned the cDNA and characterized the enzyme. The deduced amino acid sequence of shrew D1 was found to be highly homologous to other known D1s and the enzyme itself to have similar catalytic activity.