Abstract
ABSTRACT: To assess the effect of fetal hypothyroidism during late gestation on postnatal cardiovascular responsiveness, we measured heart rate and cardiac output responses to isoproterenol in newborn tombs. To evaluate the effect of such altered thyroid status on the development of β-adrenergic signaling cascade, we measured myocardial β-adrenergic receptor concentration and affinity, guanine nucleotide regulatory protein density, and adenylyl cyclase responsiveness. Twenty fetal lambs underwent either thy-roidectomy and line placement or line placement alone at 128–130 d gestation. Five thyroidectomized and six control newborns were treated with isoproterenol, five thyroidectomized and four control newborns were killed upon delivery and tissue was obtained for biochemical studies, and four additional animals were delivered and killed at 126 d gestation and tissue was obtained for receptor analysis. Of the newborns treated with isoproterenol, the thyroidectomized Iambs showed tower increase in heart rate and cardiac output compared with euthyroid newborns. Compared with the myocardium of normal newborns of similar gestation, the myocardium of the newborns who underwent fetal thyroidectomy failed to show the normal increase in β-adrenoceptors accompanied by reduction in β-adrenergic-stimulated adenylate cyclase activity. These results suggest that near term, the normal development of ovine fetus myocardial β-adrenergic receptor is affected by thyroid hormones.
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Birk, E., Tyndall, M., Erickson, L. et al. Effects of Thyroid Hormone on Myocardial Adrenergic β-Receptor Responsiveness and Function during Late Gestation. Pediatr Res 31, 468–473 (1992). https://doi.org/10.1203/00006450-199205000-00011
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DOI: https://doi.org/10.1203/00006450-199205000-00011
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