Abstract
ABSTRACT: We investigated the effect of thyroxine (T4), glucocorticoids, and T4 + glucocorticoids on the maturation of fetal rabbit brain and heart insulin receptors. Five doses of T4 over 10 days (50 μg/kg body weight per dose) were administered to the mother; significant amounts crossed the placenta (fetal serum free T4 = 0.75 ± 0.08 versus a control of 0.21 ± 0.02 ng/dl, p < 0.02) and increased the specific binding of [125I]insulin to 30-day-old fetal heart membranes from a control of 3.6 ± 0.74% per 100 μg protein to 5.8 ± 0.19% (p < 0.05). Curvilinear Scatchard plots revealed an increase in receptor number × 107 μg protein-1 from 137 ± 4 to 244 ± 39 (p < 0.05) with no change in receptor affinity. No appreciable alteration by T4 in the [125I]insulin-specific binding and receptor number of 30-day fetal brains was noted. Fetal heart glycogen content was decreased and there was a small increase in plasma glucose concentration in the T4-treated group (each p < 0.02). Betamethasone at 0.17 mg/kg did not affect the specific binding of [125I]insulin to 27-day fetal heart or brain plasma membranes, although a decrease in heart glycogen content and an increase in plasma glucose concentration were observed (each p < 0.02). Also T4 + betamethasone did not alter the [125I]insulin binding to 27-day fetal heart or brain plasma membranes, but resulted in an additive effect (a marked depletion) on cardiac glycogen (p < 0.001). Brain glycogen was undetectable in all fetuses, control of treated (regardless of the type of hormonal treatment). Thus T4 and glucocottcoids produce different effects on developing fetal brain and heart insulin receptors, alon with a depletion of the myocardial glycogen stores.
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Devaskar, S., Grim, P. & Devaskar, U. A Differential Effect of Thyroxine and Glucocorticoids on Fetal Brain and Heart Insulin Receptor. Pediatr Res 19, 192–198 (1985). https://doi.org/10.1203/00006450-198502000-00009
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DOI: https://doi.org/10.1203/00006450-198502000-00009