Abstract
Embryonic rat myocardium was grafted into the anterior eye chamber (in oculo) of adult host rats in a series of two experiments that studied the effects of thyroid hormones [triiodothyronine (T3) and thyroxine (T4)] on heart tissue developing without hemodynamic load. In each experiment, surgical sympathectomy of one eye chamber was used to define possible interactions between thyroid hormones and sympathetic innervation to the graft. In the first experiment, propylthiouracil (PTU, 20 mg/kg sc) greatly suppressed growth and beating rate of whole heart grafts, while excess T4 (0.1 mg/kg sc) transiently increased beating rate but not growth. In the second experiment, T3 (5 mg/21 days, slow-release pellet) failed to promote growth in ventricular grafts. However, the size of atrial grafts in surgically sympathectomized eye chambers was larger in T3-treated compared with control rats. T3 administration increased beating rate in ventricular grafts. In both experiments, thyroid hormone treatments were effective in increasing heart weight-to-body weight ratios in the host rats. The data suggest that exposure to normal levels of thyroid hormones may be necessary for optimal cardiac growth. The data also support the hypothesis that a hemodynamic load is required for thyroid hormone-induced cardiac growth.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
